CBSE Class 12

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 16 Environmental Issues. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 16 Important Extra Questions Environmental Issues

Environmental Issues Important Extra Questions Very Short Answer Type

Question 1.
What are pollutants?
Answer:
The substances causing pollution are termed pollutants.

Question 2.
What is the source of aerosols?
Answer:
Smoke, ash, soot.

Question 3.
What photochemical oxidants pollute the air?
Answer:
Peroxyacetyl nitrate, ozone, and aldehyde.

Question 4.
The use of lead-free petrol or diesel is recommended to reduce the pollutants emitted by automobiles. What role does leadership play?
Answer:
Lead inactivates the catalytic converter.

Question 5.
In which year was the Air (Prevention and Control of Pollution) Act amended to include noise as an air pollutant?
Answer:
In 1987.

Question 6.
Name the city in our country where the entire public road transport runs on CNG.
Answer:
Delhi.

Question 7.
It is a common practice to undertake desilting of overhead water tanks. What is the possible source of silt that gets deposited in the water tanks?
Answer:
The soil particles carried by water from a source of the water supply.

Question 8.
What is cultural eutrophication?
Answer:
Faster aging of a lake due to the presence of large amounts of industrial, agricultural wastes, and domestic sewage produced by human activities is called cultural or accelerated eutrophication.

Question 9.
List any two adverse effects of particulate matter on human health.
Answer:

1. Breathing and respiratory problems like bronchitis, asthma, inflammation of lungs, etc.
2. Cardiovascular disorders and premature death.

Question 10.
Why are tall chimneys recommended for factories?
Answer:
To reduce air pollution at ground level.

Question 11.
Name the biggest source of air pollution in large cities.
Answer:
Automobiles.

Question 12.
Why is CNG better than diesel? (CBSE Outside Delhi 2016)
Answer:
CNG burns most efficiently in automobiles and very little of it is left unburnt. It is cheaper and cannot be easily adulterated.

Question 13.
What is the frequency of infrasound and ultrasound?
Answer:

1. Infrasound below 50 Hz.
2. Ultrasound-Above 20000 Hz.

Question 14.
Name the layer of atmosphere that is associated with ‘good ozone’.(CBSE 2019)
Answer:
Stratosphere

Question 15.
What would have been the temperature at the surface of the earth without the greenhouse effect? (HOTS)
Answer:
18°C as compared to the present average of 15°C.

Question 16.
How much average global temperature will rise by the year 2100?
Answer:
1.4 – 5.8°C.

Question 17.
What are Dobson units? (CBSE Delhi 2011)
Answer:
Dobson units (DU) measure the thickness of ozone in a column of air from the ground to the top of the atmosphere.

Question 18.
Explain polar vortex.
Answer:
Antarctic air is completely isolated from the rest of the world by the natural circulation of wind called the polar vortex.

Question 19.
Name the world’s most problematic aquatic weed. What is the nature of the water body in which the weeds grow abundantly? (CBSE Delhi 2008)
Answer:

1. Eichhornia
2. Highly polluted freshwater bodies containing organic waste.

Question 20.
Write the name of the organism that is referred to as ‘Terror of Bengal’. (CBSE Delhi 2014)
Answer:
Eichhornia (Water hyacinth).

Question 21.
State the cause of Accelerated Eutrophication. (CBSE Delhi 2014)
Answer:
Nutrient enrichment due to the addition of pollutants from industries and homes into water bodies causes accelerated eutrophication.

Environmental Issues Important Extra Questions Short Answer Type

Question 1.
An electrostatic precipitator in a thermal power plant is not able to generate a high voltage of several thousand. Write the ecological implication because of it. (CBSE 2017)
Answer:
It will not be able to remove particulate matter present in the exhaust of thermal power plants. Hence it cannot control pollution as dust particles will be released into the air.

Question 2.
List four benefits to human life by eliminating the use of CFCs. Suggest two practices giving one example of each that helps protects rare or threatened species. (CBSE 2017)
Answer:
Benefits to human life by eliminating the use of CFCs:

1. Ozone depletion will be prevented.
2. The greenhouse effect will be controlled.
3. Global warming will be controlled.
4. It will prevent old climatic changes that take place due to a rise in temperature.

Two practices that help, protect rare or threatened species are:

1. Ex-situ conservation: In this, organisms are taken out of their natural habitat and kept at a special care location. Example: Botanical garden, zoo, etc.
2. In situ conservation: Here the species are conserved in their natural habitat. Example: Natural park, sanctuaries.

Question 3.
Why are microbes like Spirulina being produced on a commercial scale? Mention its two advantages. (CBSE Delhi 2018C)
Answer:
Spirulina is produced on a commercial scale due to the following reasons:

1. Spirulina is a rich source of protein. It can be used to solve the problem of hunger and malnutrition.
2. It also reduces environmental pollution as it utilizes the waste as raw material which otherwise pollutes the environment.

Question 4.
Classify pollution on the basis of origin.
Answer:
Types of pollution on the basis of origin:

1. Natural, e.g. volcanic eruption.
2. Anthropogenic, e.g. man-made such as industrial pollution.

Question 5.
What are the two main sources of air pollution?
Answer:

1. Fixed sources: Which include large factories, electrical power plants, mineral smelters, small industries.
2. Mobile sources: They include all sorts of transports.

Question 6.
What are the effects of carbon monoxide?
Answer:
Carbon monoxide (CO) is a product of the incomplete combustion of fossil fuels. Nearly 50% of all CO emission originates from automobiles. It is also present in cigarette smoke. CO is short-lived in the atmosphere and gets oxidized to CO₂. Carbon monoxide is highly poisonous to most animals. When inhaled, CO reduces the oxygen-carrying capacity of the blood.

Question 7.
Write the names of four main gases which pollute the air.
Answer:
C0₂, CO, N0_2, and S02 pollute the air.

Question 8.
Differentiate between primary air pollutants and secondary air pollutants.
Answer:
Differences between primary air pollutants and secondary air pollutants:

Question 9.
What are the effects of air pollution? How can it be minimized?
Answer:
Effects of air pollution: Atmospheric pollution causes respiratory and vascular diseases in humans, produces fluorosis in livestock, adversely affects plants and buildings, and poses a threat to the climate.

Control of air pollution: Air pollution can be minimized by separating pollutants from harmless gases, or by converting them to harmless substances before releasing the industrial and motor vehicle exhausts into the atmosphere.

Question 10.
What is particulate matter? How does particulate matter affect the biological world?
Answer:
Suspended Particulate Matter (SPM): The solid particles or liquid droplets (aerosols) remain suspended in the air. For example, smoke, soot, dust, asbestos, etc. SPM above the size of 10 mm is trapped by nasal hair, pharyngeal, tracheal, and bronchial mucus. The same is coughed out or deposited in the nose as nasal scales. Smaller particles of SPM reach the alveoli.

There they may be attacked by phagocytes or pass into living cells. SPM causes irritation in the respiratory tract, bronchitis, and lung diseases. These particles may cause asbestosis, pneumoconiosis, etc. They also result in reduced visibility.

Question 11.
What is photochemical smog? How smog affects the biological world?
Answer:
1. Photochemical Smog: It is a secondary pollutant. It is yellowish-brown smog that is formed under oxidizing conditions and high temperatures over cities and towns that are releasing a lot of nitrogen oxides and unburnt hydrocarbons. In still air, the two interact photochemically to produce photochemical oxidants-ozone, PAN, aldehydes, and phenols. Photochemical smog does not have any appreciable amount of primary pollutants. It is also called Los Angeles smog.

2. Effect on the biological world: It causes bleaching of foliage of certain plants. It also causes silvering, glazing, and necrosis of the leaves. It causes respiratory problems in animals.

Question 12.
What is acid rain? What are its effects on plants?
Answer:
Acid rains: Sulphur dioxide and sulfur trioxide are produced by the oxidation of sulfur in fossil fuels. Similarly, nitrogen dioxide or nitrogen monoxide are released through vehicular emissions. These gases react with water and form sulphuric acid, sulfurous acid, or nitric acid. These acids when precipitated as rain or snow create acid rain or acid precipitation. The pH of acid rain is less than 5-6 and could be as low as 4. Acid rain adversely affects plant vegetation by causing chlorosis and necrosis.

Question 13.
Write the effects of hydrocarbons (HCs).
Answer:
Effects of hydrocarbons:

1. Benzene and its derivatives are carcinogens.
2. Formaldehyde causes indoor pollution. It contributes to photochemical smog. Inhaling formaldehyde can cause respiratory irritation.
3. Some reactive HCs contribute to the formation of secondary pollutants.

Question 14.
What is the relation between epiphytic lichen and air pollution?
Answer:
Epiphytic lichens are reliable indicators of air pollution and can often be ranked on a sensitivity scale to estimate changing level of atmospheric pollution, especially of S02. The presence or absence of certain epiphytic lichens in a given locality and the pattern of their distribution can be related to the extent of pollution in the area.

Question 15.
How is air pollution responsible for changing the ill effects of ultraviolet radiation?
Answer:
Air pollution is enhancing the ill effects of UV radiation. Fluorocarbons are threatening and depleting the ozone layer of the stratosphere, thus allowing the UV radiations to reach this planet. The UV radiations cause serious damages to life by damaging nucleic acids in living organisms.

Question 16.
Mention any two examples of plants used as windbreakers in the agricultural fields.
Answer:
Windbreakers or shelterbelts provide shelter from wind and protect soil from erosion. Jamun and Imli and some other trees like Babul, Lawsonia, Thevetia, and Calotropis act as windbreakers in the agricultural field.

Question 17.
It is true that carpets and curtains/drapes placed on the floor or wall surfaces can reduce the noise levels. Explain briefly.
Answer:
Yes, it is true that placing carpets on the floor and curtains on the wall surface, windows, reduce the noise level. This is because the curtains and carpets on the wall surface act as muffling devices and absorb sounds of moderate level.

Question 18.
What is hybrid vehicle technology? Explain its advantages with a suitable example.
Answer:
The technology used to run vehicles on dual-mode like petrol or compressed natural gas is said to be hybrid vehicle technology. These vehicles run on either petrol or CNG. As CNG is a clean and green fuel so it is helpful to reduce environmental pollution and also to conserve petrol and other fossil fuels.

Question 19.
Is it true that if the dissolved oxygen level drops to zero the water will become septic? Give an example that could lower the dissolved oxygen content of an aquatic body.
Answer:
Yes, the water becomes septic if the dissolved oxygen drops to zero. Organic pollution (biodegradable) is an example.

Question 20.
Name any one of the greenhouse gases and their possible source of production on a large scale. What is the harmful effect of it?
Answer:
C02 and Methane. C02 levels are increasing due to the burning of fossil fuels leading to global warming.

Question 21.
It is a common practice to plant trees and shrubs near the boundary walls of buildings. What purpose do they serve?
Answer:
The plants growing near the boundary wall act as barriers to sound pollution and act as dust catchers.

Question 22.
Why has the National Forest Commission of India recommended a relatively larger forest cover for hills than the plains?
Answer:
National Forest Commission in its National Forest Policy (1988) has recommended 33 percent forest cover for the plains and 67 percent for the hills because plains mainly provide land for human settlements. Forests on the hills prevent soil erosion and landslides.

Question 23.
How can slash and burn agriculture become environment-friendly?
Answer:
Slash and burn agriculture can become environment-friendly if rows of trees and shrubs are left intact while clearing the area for cultivation. This will prevent soil erosion and the invasion of weeds. There will be a quicker recovery of the forest after the area is abandoned.

Question 24.
What is the main idea behind the “Joint Forest Management Concept” introduced by the Government of India?
Answer:
It is government-private entrepreneurship for upkeeping forests. The forest department prepares the plan, procures saplings and equipment for planting and plant protection. The locals take care of the plants till they become mature. For this, they get an honorarium and share in plant products. This sort of management provides livelihood to locals and protection to plants against stealing and illegal felling of trees.

Question 25.
What do you understand by snow blindness?
Answer:
Snow blindness is temporary blindness caused by inflammation of the cornea due to absorption of UV-B radiations. It is accompanied by photo burning and dimming of eyesight after which cataract develops. Regular exposure to UV-B radiations causes permanent damage to the cornea resulting in blindness.

Question 26.
What is water pollution?
Answer:
Water pollution: The addition of harmful materials to water is termed water pollution. The sources of inland water pollution are community wastewater (sewage) and wastes from industries and agricultural practices. Water pollutants include organic matter, pathogens, chemicals and minerals, solid particles, radioactive wastes, and heat.

Question 27.
What are two serious problems with the use of nuclear energy?
Answer:
Nuclear energy has two most serious problems:

1. The accidental leakage of radioactivity
2. The safe disposal of radioactive wastes.

Question 28.
Particulate and gaseous pollutants along with harmless gases are released from the thermal power plants.
(i) Name any two harmless gases released.
Answer:
Nitrogen and oxygen.

(ii) Name the most widely used device for removing particulate pollutants from the air. Explain how the device is used? (CBSE 2009)
Answer:
Electrostatic precipitator: Working of electrostatic precipitator The device has electrode wires kept at very high voltage in order to produce corona that releases electrons. These electrons provide dust particles a negative charge. The device has a collecting plate that is grounded. So when air with dust rushes through the device, the negatively charged dust is trapped at the collecting plate.

Question 29.
Study the graph given below and answer the questions that follow:
(i) What is the relationship between dissolved oxygen and biochemical oxygen demand (BOD)?
(ii) Mention their effect on aquatic life in the river. (CBSE 2008)

Answer:
(i) BOD indicates the quantity of wastewater. BOD refers to the amount of dissolved oxygen required by bacteria in decomposing oxygen.

Thus greater the BOD, the lesser will be dissolved oxygen. A sudden decline in dissolved oxygen causes the death of many aquatic organisms.

(ii) There is a sharp decline in the dissolved organic waste downstream from the point of discharge. More the dissolved oxygen, the healthier will be the aquatic life and vice versa.

Question 30.
A crane had a DDT level of 5 ppm in its body. What would happen to the population of such birds? Explain giving reasons. (CBSE 2009)
Answer:

1. Fish-eating bird crane has a DDT level of 5 ppm due to biomagnification.
2. The high concentration of DDT disturbs calcium metabolism in birds.
3. It causes thinning of eggshells and premature breaking of the egg.
4. There will be a decline in the bird population.

Question 31.
Study the graph given below. Explain how is oxygen concentration affected in the river when the sewage is discharged into it. (CBSE Delhi 2011)
Answer:
The figure shows the changes as a result of sewage discharged into the river. Micro-organisms involved in the biodegradation of organic matter in the receiving water body consume a lot of oxygen. As a result, there is a sharp decline in dissolved oxygen downstream. It causes the death of a large number of fishes and other aquatic creatures.

Question 32.
“Determination of Biochemical Oxygen Demand (BOD) can help in suggesting the quality of a water body” Explain. (CBSE Delhi 2015)
Answer:
The quality of the water body depends upon the organic wastes present in it. More is the amount of organic wastes present, poorer is the quality of water body for human consumption. The number of organic wastes can be determined by the BOD of that water body, e.g. BOD of pure drinking water is less than one, below 1500 mg/liter for weak organic wastewater but is more than 4000 mg/liter for a highly polluted water body.

Question 33.
Discuss the role of women and communities in the protection and conservation of forests.
Answer:
Role of women and communities in the protection and conservation of forests:

1. In 1731, the Bishnoi community led by a woman Amrita Devi obstructed the cutting of trees by hugging the tree and asked the workers of the king to cut her before cutting the tree. Her three daughters and hundreds of other Bishnois lost their lives in saving trees.
2. Chipko movement started by Chandi Prasad Bhatt and Sunder Lai Bahuguna of Silyara in the Tehri region when workers of the contractor were not allowed to cut the trees by village people by hugging around them.

Question 34.
Explain the different steps involved during the primary treatment phase of sewage. (CBSE Delhi 2015)
Answer:
Primary treatment of wastewater in sewage treatment plants involves mechanisms like floatation, Alteration, and sedimentation so as to remove insoluble and stable solid wastes. The final product after primary treatment is called primary sludge.

Question 35.
How have human activities caused desertification? Explain. (CBSE Delhi 2013)
Answer:
Desertification caused by human activities. The development of the fertile topsoil takes centuries. But it can be removed very easily due to human activities.

• Over-cultivation
• Unrestricted grazing
• Deforestation
• Poor irrigation practices.

All these human activities result in arid patches on land. When large barren patches extend and meet over time a desert is created.

Thus desertification is a major problem particularly due to increased urbanization.

Environmental Issues Important Extra Questions Long Answer Type

Question 1.
Define pollution. Compare the biodegradable and non-biodegradable pollutants.
Answer:
Pollution: “Environmental pollution is an unfavorable alteration of our surroundings largely as a by-product of man’s actions through direct or indirect effects of changes in energy patterns, radiation levels, chemical and physical conditions and abundance of organisms.”

Differences between biodegradable and non-biodegradable pollutants:

Question 2.
What is air pollution? List various air pollutants.
Answer:
Air pollution: The release of harmful materials into the air is called air or atmospheric pollution. It is the degradation of air quality and atmospheric conditions.

Air pollutants include gaseous materials, suspended particles, and radioactive substances.
1. The gaseous pollutants of the air come from combustion in motor vehicles and industries. These include CO, C0₂, NO, N0₂, S0₂, S0₃, hydrocarbons, fluorides, and photochemical oxidants such as peroxyacetyl nitrate (PAN), ozone (0₃), and aldehydes. PAN is a secondary pollutant formed in the air by the interaction between nitrogen oxides and hydrocarbons in the presence of sunlight. It is more toxic than the primary pollutants. An increase in toxicity by the reaction among pollutants is called synergism.

2. The particulate contaminants of air also come from industries and automobiles. These include fly-ash, soot, metal dust, cotton fibers, asbestos, fibers, lead, aerosols (chlorofluorocarbons or CFCs), polychlorinated biphenyls (PCBs), tobacco smoke, smog, pollen, spores, cysts, and bacteria.
(in) Radioactive substances released by nuclear explosions and war explosives are also very harmful air pollutants.

Question 3.
Define a pollutant. How many types of pollutants are there?
Answer:
Pollutant: It is a substance (e.g. dust, smoke), chemical (e.g. S0₂), or factor (e.g. heat, noise) that on release into the environment has an actual or potentially adverse effect on human interests. A pollutant can also be defined as a constituent in the wrong amount, at the wrong place, or at the wrong time.

Question 4.
What measures do you suggest to control pollution from automobile exhaust?
Answer:
Control of pollution from automobile exhaust:

1. Efficient engines can reduce the number of unburnt hydrocarbons from vehicuLar emissions.
2. Use of cataLytic converters to convert harmful gases to harmless.
3. Use of good quality fuel.
4. Unleaded petroL can reduce the amount of lead in the exhaust.
5. The use of CNG (compressed natural gas) Lowers the toxic contaminants in the exhaust.

Question 5.
Blends of polyblend and bitumen, when used, help to increase road life by a factor of three. What is the reason?
Answer:
Polyblend is a fine powder of recycled modified plastic. The binding property due to increased cohesion and enhanced water-repelling property of plastic makes the road last longer besides giving added strength to withstand more loads.

This is because:

• Plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently crosses 45°C.
• Rainwater will not seep through because of the plastic in the tar.

Question 6.
“Indiscriminate human activities have strengthened the greenhouse effect resulting in Global Warming.” Give the relative contribution of various Greenhouse Gases in the form of a pie chart and explain the rate of the energy of sunlight reaching the earth’s surface contributing towards Global Warming. (CBSE Sample Paper 2020)
Answer:
a)
(b) Rate of the energy of sunlight:

• Clouds and gases reflect one-fourth of incoming solar radiations.
• Some of the energy is absorbed by clouds and gases.
• Thus only half of the solar energy falls on the surface of the earth.
• The small amount of energy is reflected back.
• Earth surface re-emits heat in the form of infrared radiations.
• The major fraction of solar energy is absorbed by atmospheric gases.

Question 7.
How does a scrubber function?
Answer:
Scrubber: A scrubber can remove gases like sulfur dioxide. In a scrubber, the exhaust is passed through a spray of water or lime. Water dissolves gases and lime reacts with sulfur dioxide to form a precipitate of calcium sulfate or sulfite.

Question 8.
Discuss the causes and effects of global warming.
Answer:
Global warming: The increase in global mean temperature due to the enhanced greenhouse effect is called global warming.

Effects of global warming:
1. Effect on weather and climate.
(а) The average temperature of the earth may increase by 1.4° to 5.8°C by the year 2100.
(б) Winter precipitation may decrease at lower altitudes.
(c) Frequency of droughts, floods may increase.
(d) Climatic change is a threat to human health in tropical and subtropical countries.

2. Sea level change. Sea level had been raised by 1 to 2 mm per year during the 20th century. It is predicted that by the year 2100, the global mean sea level can increase up to 0.88 m over the 1990 level. Global warming may contribute to sea-level rise due to the thermal expansion of the ocean.

3. Effect on a range of species distribution. Vegetation may extend 250-600 km poleward with a global rise in temperature by 2 to 5°C during the 21st century.

4. Effect on food production. Increased temperature will cause an eruption of plant diseases and pests and vast growth of weeds.

Question 9.
Show the relative contribution of greenhouse gases to total global warming.
Answer:
Greenhouse gases:

The relative contribution of various greenhouse gases to total Global warming.

Question 10.
Make a chart illustrating the kinds of water pollutants.
Answer:
Classification of water pollutants:

Question 11.
List four laws that enforce control of pollution.
Answer:
1. The Environment (Protection) Act, 1986: This act clearly brings the protection of air, water, and soil quality, and the control of environmental pollutants including noise under its purview.

2. The Insecticide Act, 1968: This act deals with the regulation of import, manufacture, sale, transport, distribution, and use of insecticides with a view to preventing risk to human health and other organisms.

3. The Water (Prevention and Control of Pollution) Act, 1974: This act deals with the preservation of water quality and the control of water pollution with a concern for the detrimental effects of water pollutants on human health and also on the biological world.

4. The Air (Prevention and Control of Pollution) Act, 1981: The act deals with the preservation of air quality and the control of air pollution with a concern for the detrimental effects of air pollutants on human health and also on the biological world. In 1987, important amendments of the Air Act 1981 were made and the noise was recognized as an air pollutant.

5. Many countries have enacted legislation to control noise. India enacted the Air (Prevention and Control of Pollution) Act, 1981 and as per this, noise pollution has been declared as an offense.

Question 12.
A factory drains its wastewater into the nearby lake causing algal bloom.
(i) How was the algal bloom caused?
Answer:
An algal bloom is caused due to enrichment of water with nutrients such as nitrogen and phosphorus. As fertility increases plant life increases.

(ii) What would be the consequences?
Answer:
Water becomes unfit for aquatic fauna because of scum and unpleasant odors. The fish and other organisms die because of a shortage of oxygen.

(iii) Name the phenomenon that caused it. (CBSE2008)
Answer:
Eutrophication.

Question 13.
Explain accelerated eutrophication. Mention any two consequences of this phenomenon. (CBSE 2009)
Answer:
Accelerated eutrophication: The natural aging of a lake by the biological enrichment of its water is called eutrophication. However, if pollutants from man’s activities like effluents from industries and homes radically accelerate the aging process, it is called accelerated cultural eutrophication.

Consequences:

• There is excess growth of algae causing algal bloom that gives an unpleasant odor.
• There is a shortage of oxygen which causes the death of the fauna of the water body.
• Ultimately death of the lake occurs.

Question 14.
How does algal bloom destroy the quality of a freshwater body? Explain. (CBSE Delhi 2013)
Answer:
Algal bloom destroys the quality of the freshwater body. Phosphorus and nitrates dissolved in polluted water act as nutrients for the green algal plants. These pollutants accelerate the growth of algae that may form a mat on the water surface. It is termed an algal bloom.

Effect:

1. The algae use oxygen at night and deoxygenate the water enough to kill the fish and other aquatic animals.
2. The algal mat on the water surface blocks light, making it unavailable for submerged plants.
3. The algae and dead organisms feed the oxygen-consuming bacteria.
4. Silt and decaying matters accumulate and finally fill the water body (lake or pond). This process is called senescence.
5. It is a natural stage in the change of water body into dry land and it becomes barren. Ultimately death of the water body occurs.

Question 15.
How did a citizen group called Friends of Areata March, Areata, California, USA, help to improve the water quality of the marshland using Integrated Waste Water Treatment? Explain in four steps. (CBSE 2018)
Answer:
Wastewater including sewage can be treated in an integrated manner by utilizing a mix of artificial and natural processes, which are as follows:

1. First of all the conventional sedimentation, filtering, and chlorine treatments are given. However, after this stage, a lot of dangerous pollutants like dissolved heavy metals still remain.
2. To combat this, an innovative approach was taken. The biologists developed a series of six connected marshes over 60 hectares of marshland.
3. Appropriate plants, algae, fungi, and bacteria were seeded into this area, which neutralizes, absorbs, and assimilates the pollutants. Hence, as the water flows through the marshes, it gets purified naturally.
4. The marshes also constitute a sanctuary, with a high level of biodiversity in the form of fishes, animals, and birds.

Question 16.
List the control measures for minimizing air pollution.
Answer:
Control measures for minimizing air pollution:

1. Simple combustible solid wastes should be burnt in incinerators.
2. Automobiles must be either made to eliminate the use of gasoline and diesel oil or complete combustion is obtained in the engine so that harmful products are omitted.
3. There should be a cut in the use of agricultural sprays.
4. Excessive and undesirable burning of vegetation should be stopped.
5. Smoking should be stopped.
6. Use of electrostatic precipitators and filters in the factories to minimize atmospheric pollution.
7. The use of tall chimneys can substantially reduce the concentration of pollutants at the ground level.
8. Weather forecasts can help in controlling air pollution as the meteorological conditions affect the dispersion, dilution, and mixing of various emissions and proper operation of factory schedule, e.g. when atmospheric stagnation or calm is predicted, a power plant should switch over from coal to gas.
9. Separation of pollutants from harmless gases.
10. Dispersion of pollutants to innocuous (harmless) products before releasing into the atmosphere.

Question 17.
Why is the ozone layer in the stratosphere called a protective layer?
Answer:
Ozone layer as a protective layer: The ozone layer in the stratosphere is very useful to human beings because it absorbs the major part of harmful ultraviolet radiation coming from the sun. Therefore, it is called a protective layer. However, it has been observed that the ozone layer is getting depleted. One of the reasons for the depletion of the ozone layer is the action of aerosols spray propellants.

Chemicals such as fluorocarbons and chlorofluorocarbons are used as aerosol propellants. These compounds react with ozone gas in the atmosphere thereby depleting it. Scientists all over the world are worried about the destruction of the ozone layer. If the ozone layer in the atmosphere is significantly decreased, these harmful radiations would reach the earth and would cause many damages such as skin cancer, genetic disorders in man and other living forms. Efforts are being made to find substitutes for these chemicals that do not react with ozone.

Question 18.
Why industrial effluents are more difficult to manage than municipal sewage? Name a disease that is caused by heavy metal contamination.
Answer:
Industrial effluents released into water contain toxic substances, such as arsenic, cadmium, lead, zinc, copper, mercury, and cyanides, besides some salts, acids, and alkalies. All these materials can prove harmful to health. They may reach the human body. Minamata is a disease caused by heavy metal (Mercury) contaminated water.

Question 19.
What is deforestation? List the causes of deforestation.
Answer:
Deforestation: According to an estimate, almost 40% of forests have been lost in the tropics and 1% of forests in the temperate region. In India, at the beginning of the twentieth century, forests covered about 30% of land whereas, by the end of the century, it reduced to 19.4%. The National Forest Policy (1988) has recommended 33% forest cover for plains and 67% for hills.

Causes of Deforestation:

• Forests are converted into agricultural land to feed the growing human population.
• Forests are cleared for making homes and establishing industries.
• Trees are felled for timber, firewood, etc.
• Jhum cultivation in the north¬eastern states has contributed to deforestation.

Question 20.
List all the wastes that you generate, at home, school, or during your trips to other places that you could very easily reduce. Which would be difficult or rather impossible to reduce?
Answer:
List of wastes:

1. Papers, clothes, polythene bags
2. Disposable crockery
3. Aluminum foil, cans
4. Leftover of tiffins
5. Wood
6. Sewage

Wastes that can be reduced:

1. Papers, clothes,
2. Leftover of tiffins.

Wastes that cannot be reduced:

1. Aluminum foil cans
2. Disposable crockery
3. Polythene bags

Question 21.
Why ozone hole form over Antarctica? How will enhanced UV radiations affect us?
Answer:
Ozone hole: During the period 1956-1970 the springtime O₃ layer thickness above Antarctica varied from 280 to 325 Dobson unit. Thickness was sharply reduced to 225 DU in 1979 and 136 DU in 1985. Antarctic air is completely isolated from the rest of the world by the natural circulation of wind called the polar vortex. The decline in ozone layer thickness during that springtime is called ozone hole. It was first noted in 1985 over Antarctica.

Effects of UV radiation on humans:

• In humans, the increase in UV radiation increases the incidence of cancer (including melanoma).
• Reduces the functioning of the immune system.
• The cornea absorbs UV-B radiations, and a high dose of UV-B causes inflammation of the cornea called snow blindness, cataract, etc. Exposure may permanently damage the cornea and cause blindness.

Question 22.
Write critical notes on:
(i) Eutrophication
Answer:
Eutrophication: The process by which a body of water becomes barren either by natural means or by pollution, extensively rich in dissolved nutrients. It results in the increased primary productivity that often leads to seasonal deficiency in dissolved oxygen. Less dissolved oxygen ultimately affects aquatic life.

Algal bloom: Phosphorus and nitrates dissolved in water act as nutrients and accelerate the growth of algae that may form a mat on the water surface. It is termed algal bloom.

Effects: The algae use oxygen at night and may deoxygenate the water enough to kill the fish and other animals. The algal mat at the water surface may block light to the submerged plants. The algae may die and sink, and feed the oxygen-consuming bacteria. They may be pushed onto the shore by wind and decompose, releasing foul gases, such as hydrogen sulfide. Silt and decaying matter may accumulate and finally fill the lake or pond. This process is called senescence. It is a natural stage in the change of a lake into dry land and it becomes barren.

(ii) Biological magnification (CBSE 2015, 2019 C)
Answer:
Biological magnification: The phenomenon in which the harmful pollutants (such as pesticides) enter the food chain and get concentrated more and more at each successive trophic level of organisms is called biological magnification.

This phenomenon is well known for mercury and DDT. The figure given ahead shows the biomagnification of DDT in an aquatic food chain. Zooplankton (tiny floating animals in the food chain), accumulated modest levels of DDT. However, small fish, forming the next level of the food chain, must eat zooplankton several times their own weight, and thus they accumulated more DDT.

In this manner, the concentration of DDT magnified at successive trophic levels, starting with 0.003 ppb (ppb = parts per billion) in water it ultimately reached 25 ppm (ppm = parts per million) in fish-eating birds. High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshells and their premature breaking eventually causing a decline in the bird population.

Biomagnification of DDT in an aquatic food chain.

(iii) Groundwater depletion and ways for its replenishment. (CBSE 2012)
Answer:
Groundwater depletion and ways for its replenishment: Underground water is most pure and safe for drinking. It is getting polluted particularly in industrial towns. The common sources of underground water pollution are sewage and industrial effluents spilled over the ground. The fertilizers and pesticides used in fields also act as pollutants. Pollution is also increased due to seepage from refuse dumps, septic tanks, and seepage pits. Method to control. Sewage and factory wastes should be treated to clean them before their release into water sources.

Question 23.
List various measures for control of noise pollution.
Answer:
Control of noise pollution:

1. Construction of soundproof rooms for noisy machines in industries.
2. Radios and transistors should be kept at low volume.
3. The use of horns with jarring sounds should be banned.
4. Noise-producing industries, aerodromes, railway stations, etc. should be shifted away from the inhabited areas.
5. Proper laws should be enforced to check the misuse of loudspeakers and public announcement systems,
6. Need to enforce a silence zone around institutions like educational institutes, residential areas, hospitals, etc.
7. Sound-absorbing techniques like acoustical furnishing should be extensively employed.
8. Noise should be deflected away from the receiver by using mechanical devices.
9. The green muffler scheme involves growing green plants along roadsides to reduce noise pollution.

Question 24.
What measures, as an individual, you would take to reduce environmental pollution? (CBSE Delhi 2011)
Answer:
Role of individuals in reducing pollution:

1. Use of unleaded petrol or CNG in vehicles as fuel.
2. Use of reformulated gasoline to save ozone in the atmosphere.
3. The use of power generators in residential areas should be avoided.
4. Plantation of trees.
5. Excessive and unplanned use of fertilizers should be avoided.
6. Biodegradable material should be used.
7. Do not blow the horn with a jarring sound.
8. Radio, transistors, T.V., Music systems should be kept at low volume to control noise pollution.

Question 25.
Discuss briefly the following:
(i) Radioactive wastes
Answer:
(i) Radioactive wastes: Radioactive wastes are of three types depending on the amount of radioactivity.
(a) Low-level radioactive wastes.
(b) Intermediate level radioactive wastes.
(c) High-level radioactive wastes.

The use of nuclear energy has two most serious problems. The first is accidental leakage and the second is safe disposal of radioactive wastes. Wastes from atomic power plants come in the form of spent fuels of uranium and plutonium. People working in such power plants, nuclear reactors, fuel processors, etc. are vulnerable to their exposure. These also undergo biological magnification and may reach 75,000 times in birds.

Radioisotopes. Many radioactive isotopes like C¹⁴, I¹²⁵, P^32, and their compounds are used in scientific researches. The wastewater of these research centers contains radioactive elements which may reach human beings through water and food chains.

Disposal of radioactive wastes. Such wastes are first concentrated to reduce the volume and then kept for 50-100 years in small ponds within the premises of nuclear power plants. This interim storage causes considerable decay of radioactivity and lessening of heat problem. It has been recommended that subsequent storage should be done in suitably shielded containers buried within the rocks, about 500 m deep inside Earth. However, this method of disposal is meeting stiff opposition from the public.

(ii) Defunct ships and e-wastes.
Answer:
Defunct ships and e-wastes: Defunct ships are a kind of solid waste requiring proper disposal. Such ships are broken down in developing countries because of cheap labor and scrap metal. They often contain toxic substances such as asbestos, polychlorinated biphenyls, tributyltin, lead, and mercury.

Similarly, irreparable computers and electronic goods are known as electronic wastes of e-wastes. Most of them are shipped to developing countries for metals like copper, nickel, silicon, gold and are recovered by recycling. Recycling is the only solution for the treatment of such wastes, provided it is carried out in an environment-friendly manner. An international treaty called Basel Convention drafted in Basel (Switzerland) as a result of great demand from developing countries.

(iii) Municipal solid wastes.
Answer:
Municipal Solid Wastes: Solid wastes refer to everything that goes out in the trash. Municipal solid wastes are wastes from homes, offices, stores, schools, etc. that are collected and disposed of by the municipality. The municipal solid wastes generally comprise paper, food wastes, glass, metals, rubber, leather, textile, etc. Burning reduces the volume of the wastes, although it is generally not complete and open dumps often serve as the breeding ground for rats and flies.

Management of municipal solid wastes:

1. Sanitary landfills were adopted as the substitute for open-burning dumps. In a sanitary landfill, wastes are dumped in a depression or trench after compaction and covered with dirt every day.
2. Municipal solid wastes, containing biodegradable organic wastes, can be transformed into organic manure for agriculture.
3. Sewage sludge and industrial solid wastes are used as landfills.
4. Hazardous metal-containing wastes are used as bedding material for road construction.
5. Other options are incineration of wastes and using emitted heat in electricity generation, and recycling various components of wastes.

Question 26.
What initiatives were taken for reducing vehicular air pollution in Delhi? Has the air quality improved in Delhi?
Or
Explain any three measures which will control vehicular air pollution in Indian cities. (CBSE 2009)
Answer:
Automobiles are the major sources of air pollution in Delhi because it has a very high number of cars.

Some specific measures taken to reduce vehicular air pollution are as follows.

• Use of CNG (Compressed Natural Gas) for its public transport system.
• Phasing out of old vehicles.
• Use of unleaded petrol.
• Use of low sulfur petrol and diesel.
• Use of catalytic converter in vehicles.
• Application of Euro II norms for vehicles.

Because of the above-mentioned steps taken up by the Government, the air quality of Delhi has improved with a substantial fall in carbon monoxide, oxides of sulfur, and nitrogen levels between 1997 and 2005.

Question 27.
Discuss briefly the following:
(i) Greenhouse effect
Answer:
Greenhouse effect: Earth’s temperature is maintained by reradiated infrared radiations by CO₂, CH₄, O₃, NO, and N0₂ and slightly by water vapors in the atmosphere. These gases prevent heat from escaping to outer space, so are functionally comparable to glass panels of a greenhouse and are called greenhouse gases (GHGs) and phenomena called the greenhouse effect. The CO₂ is added to the atmosphere mainly by burning fossil fuels, volcanic activities, etc.

Greenhouse gases are useful in keeping the earth warm with an average temperature of 15° C. In their absence, the surface temperature of the earth will be as low as 18° C. This temperature will freeze all water and kill most life. However, excess greenhouse gases are equally harmful. Over 7 × 10¹² kg of CO₂ is being added annually to the atmosphere by the burning of fossil fuels. As a result, the CO₂ concentration of the atmosphere has risen from 0.028% in 1800 to .0359% in 1994. Now enhanced greenhouse effect is resulting in Global Warming.

(ii) Catalytic converters
Answer:
Catalytic converters: Catalytic converters, having expensive metals namely platinum-palladium and rhodium as catalysts, are fitted into automobiles for reducing the emission of harmful gases. As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas, respectively. Motor vehicles equipped with catalytic converters should use unleaded petrol because leaded petrol inactivates the catalyst.

It has been established that the installation of catalytic converters can slash carbon monoxide emissions from 90 grams to 3.4 grams per mile run. So if half the vehicles on Delhi and Mumbai roads are made to install such catalytic converters, then total CO emission in India can be reduced by 70 percent.

(iii) Ultraviolet B
Answer:
Ultraviolet-B radiations: These are high energetic UV-radiations that are mostly blocked by the ozonosphere located in the stratosphere of the atmosphere. But due to the increased production of ozone-depleting substances (ODS) like CFCs, halons, etc., the ozone shield is becoming thinner and thinner. This is increasing the amount of UV-B radiations reaching the earth’s surface. These radiations are carcinogenic.

The cornea absorbs UV-B radiation. High dose of UV-B causes inflammation of the cornea called snow blindness cataract. Exposure may permanently damage the cornea.

Question 28.
Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared a health emergency in the cities where the air quality is very severely poor.
(i) Mention any two major causes of air pollution.
Answer:
Two causes of air pollution are:
(a) Burning of fossil fuels.
(b) Industrial effluents

(ii) Write the two harmful effects of air pollution on plants and humans.
Answer:
Harmful effects of air pollution are:
(a) It affects the respiratory system of humans and animals.
(b) It also reduces the growth and yield of crops and causes premature death of plants.

(iii) As a captain of your school Eco¬club, suggest any two programs you would plan to organize in the school so as to bring awareness among the students on how to check air pollution in and around the school. (CBSE2018)
Answer:
As a captain of your school Eco-club, I shall suggest:
(a) Encouraging public transport, i.e. buses, metro, etc and using CNG/electric vehicles instead of diesel and petrol vehicles.
(b) Planting more trees to curb pollution.

Question 29.
While studying pollution of water, a group of students observed mortality of fish in the river flowing through the city and also in the pond which was away from the city but was adjacent to the crop fields. They further found that drains of the city discharged sewage into the river and the water from farms flowed into the pond. Explain how these could be the cause of fish mortality. (CBSE Delhi 2019 C)
Answer:

• Pollutants from man’s activities cause eutrophication in ponds and rivers.
• The prime contaminants are nitrates and phosphate which act as plant nutrients.
• They overstimulate the growth of algae causing the formation of a thick layer of scum on the surface and an unpleasant odor.
• The dissolved oxygen in the water decreases. It is essential for all forms of aquatic life.
• At the same time, other pollutants flowing from farms into pond poison the whole population of fish.
• As the decomposition of dead fish occurs, the dissolved oxygen content of water further decreases.
• Ultimately pond chokes to death.

Question 30.
A young sperm whale, 33-foot long was found dead off the coast. It had a large amount of human trash like trash bags, polypropylene sacks, ropes, net segments, etc. amounting to 29 kilograms in its digestive system. The whale died because of inflammation of the abdominal lining. Analyze the possible reasons for such mishaps and suggest measures that can be taken to reduce such incidents. (CBSE Sample Paper 2018-19)
Answer:

1. We are increasing the use of non-biodegradable products. In most of the products we buy, there is at least one layer of plastic in it.
2. We have started packaging even our daily use products like milk and water in polybags.
3. In cities, fruits and vegetables are packed in polystyrene and plastic packaging and we contribute heavily to environmental pollution.
4. Most of the wastes are dumped in water bodies without segregation and treatment. One has to reduce the generation of non-biodegradable wastes and stop the irresponsible dumping of wastes into water bodies.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 15 Biodiversity and Conservation. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 15 Important Extra Questions Biodiversity and Conservation

Biodiversity and Conservation Important Extra Questions Very Short Answer Type

Question 1.
Define biodiversity.
Answer:
It refers to the totality of genes, species, and ecosystem of a region, e.g. Forest.

Question 2.
Is biodiversity the same from place to place?
Answer:
No, it differs from one place to another place.

Question 3.
What is the advantage of genetically uniform crop plants?
Answer:
The monoculture of crop plants will give a high yield.

Question 4.
What is the disadvantage of genetically uniform crop plants?
Answer:
Such crop plants are highly prone to diseases.

Question 5.
What is the total number of species discovered and described presently on earth? What is the predicted number?
Answer:
1.7 million and 50 million, respectively.

Question 6.
What are the characteristics that make a community stable?
Answer:
The stability of an ecosystem is controlled by:

1. Carrying capacity,
2. Recycling of wastes,
3. Density-related self-regulation and
4. Feedback system.

Question 7.
What accounts for the greater ecological diversity of India?
Answer:
India has high ecological diversity due to a variety of topography, soil types, climates, rainfall zones, sea coasts, islands, etc. Ten well-demarcated biogeographical zones with different biota occur in India.

Question 8.
What is the difference between endemic and exotic species?
Answer:
Endemic species belong to a local area and are of limited distribution due to biotic and abiotic regulations, e.g. Lion Tailed Macaque.

Exotic species enter from outside with under distribution due to non-control of biotic and abiotic factors. They face little resistance by endemic species, e.g. Eucalyptus.

Question 9.
How does species diversity differ from ecological diversity?
Answer:
Species diversity is the occurrence of variety and abundance of species in a community while ecological diversity is the occurrence of different ecosystems and communities in a geographical area.

Question 10.
Why is genetic variation important in the plant Rauwolfia vomitoria?
Answer:
It results in differences in the potency and concentration of drug reserpine in the plant Rauwolfia vomitoria found in different regions of the Himalayas.

Question 11.
What is the advantage to a species having more genetic diversity?
Answer:
It enables the species to adjust and adapt to changed environmental conditions.

Question 12.
What are the consequences of lower genetic diversity?
Answer:
Lower genetic diversity leads to uniformity.

Question 13.
Coin a term for the following:
(i) Within community diversity
Answer:
Alpha diversity.

(ii) Between community diversity.
Answer:
Beta diversity.

Question 14.
What is the approximate drop of temperature with a corresponding increase/decrease of about 1000 m in altitude?
Answer:
There is about a 6.5° drop in temperature.

Question 15.
What is the cause of mortality of ducks, swans, and cranes?
Answer:
Lead poisoning as they take in spent gunshots that fall into lakes and marshes.

Question 16.
List two uses of the Red List.
Answer:

1. Developing awareness about the importance of threatened biodiversity.
2. Identification and documentation of endangered species.

Question 17.
The red list contains an assessment of how many species?
Answer:
18,000 species out of which 11,000 are threatened.

Question 18.
What could have triggered mass extinctions of species in the past?
Answer:
Glaciation, melting of snow, the eruption of large volcanoes, earthquakes, movement of continents, large meteorites falling on the earth, drought, etc. could have triggered mass extinctions.

Question 19.
What does ‘red’ indicate in the IUCN red list (2004)?
Answer:
‘Red’ in IUCN red list (2004) indicates the threatened species, i.e. the species under varying degrees of extinction risk categories.

Question 20.
What is the importance of cryopreservation in the conservation of biodiversity? (CBSE (Delhi) 2015)
Answer:
It serves the purpose of ex situ conservation.

Question 21.
Name the type of biodiversity represented by the following:
(a) 50,000 different strains of rice in India.
Answer:
Genetic diversity

(b) Estuaries and alpine meadows in India. (CBSE (Delhi) 2013)
Answer:
Ecological diversity.

Question 22.
Write the basis on which an organism occupies a space in its community-natural surrounding. (CBSE Outside Delhi 2013)
Answer:
Alexander von Humboldt observed that within a region species richness increased with increasing explored area up to a limit.

Question 23.
Mention the kind of biodiversity of more than a thousand varieties of mangoes in India. How is it possible? (CBSE (Delhi) 2015)
Answer:

1. Genetic diversity
2. (a) It is the measure of variation in genetic information contained in the organism.
   (b) It enables a population to adapt to the environment.

Biodiversity and Conservation Important Extra Questions Short Answer Type

Question 1.
What will be the consequences of the loss of biodiversity?
Answer:
Consequences of loss of biodiversity:

1. It would check the evolutionary capability of biota to cope up with environmental changes.
2. It would result in the extinction of species.
3. As man is dependant on food and other necessities, its loss will be hard-pressed for mankind.

Question 2.
What are the causes of the loss of biodiversity?
Answer:
Biological diversity is lost before its size is known. Causes of the toss of biodiversity:

1. Increased human population.
2. Increased consumption of resources.
3. Pollution due to human activities.

Question 3.
How many genes are present in mycoplasma, E. coli, Drosophila, Oryza sativa, and Homo sapiens?
Answer:

Question 4.
List three levels of biodiversity.
Answer:
Biodiversity can be studied at the following levels:

1. Genetic diversity
2. Species diversity
3. Ecological/Ecosystem diversity.

Question 5.
What is the basis of speciation?
Answer:
Basis of speciation. The amount of genetic variation is the basis of speciation (evolution of new species). It has a key role in the maintenance of diversity at species and community levels. The total genetic diversity of a community will be greater if there are many species, as compared to a situation where there are only a few species.

Genetic diversity within a species often increases with environmental variability.

Question 6.
Write a note on ecological diversity.
Answer:
Ecological diversity. It is related to species diversity and genetic diversity. India has a greater ecosystem diversity than a Scandinavian country. India has several ecosystems/biomes like alpine meadows, rain forests, deserts, wetlands, mangroves, coral reefs, etc.

Question 7.
List the Natural World Heritage sites of India.
Answer:
Natural World Heritage sites of India:

Question 8.
Depict with the help of simple sketches the representation of global biodiversity of major taxa of plants, invertebrates, and vertebrates. (CBSE 2009)
Answer:

Representation of global biodiversity of major taxa of plants, invertebrates, and vertebrates

Question 9.
Elaborate how invasion by an alien species reduces the diversity of an area.
Answer:
This may be due to any of the following reasons:

1. Fast-growing species may compete with less vigorous local species.
2. Alien species will proliferate in that area if their natural pests and predators are not present.
3. By amensalism, i.e. it may harm local species by producing chemicals.
4. Such species may grow vigorously and may form conditions unfavorable for the growth of local native species like Eichhornia.

Question 10.
Broadly classify the extinction processes.
Answer:
Classification of extinction processes:

1. Natural extinction: It is due to a change in environmental conditions. It is at a very slow rate.
2. Mass extinction: Mass extinction occurs due to catastrophes. In this case, a large number of species became extinct in millions of years.
3. Anthropogenic extinction: Extinction of species is due to man’s activities. It is occurring in a short period of time.

Question 11.
What is an endangered species? Give an example of an endangered plant and animal species each.
Answer:
An endangered species is a population of organisms, which is facing a high risk of becoming extinct because

• Its number is very low.
• It is threatened by changing environment.
• It is facing a predator threat. Endangered plant species-Venus fly trap Endangered animal species-Siberian tiger.

Question 12.
List the benefits of protected areas for the conservation of biodiversity.
Answer:
Benefits of protected areas:

1. Maintaining viable populations of all native species and subspecies.
2. Maintaining the number and distribution of communities and habitats, and conserving the genetic diversity of all the present species.
3. Preventing the human-caused introduction of alien species.
4. Making it possible for species/ habitats to shift in response to changes in the environment.

Question 13.
List the biosphere reserves of India.
Answer:
Biosphere reserves of India:

1. Nanda Devi
2. Nokrek
3. Manas
4. Dibru Saikhowa
5. Dean Debang
6. Sunderbans
7. Gulf of Mannar
8. Nilgiri
9. Great Nicobar
10. Simitipal
11. Ichanghendzonga
12. Pachmarhi
13. Agasthyamatai

Question 14.
Write a note on sacred forests.
Answer:
Sacred forests: These are forest patches protected by tribal communities in India and other Asian countries due to religious belief. These are undisturbed forests having no human intervention and frequently surrounded by highly degraded landscapes. Such forests are located in many states of India and have a number of rare, endangered, and endemic species. Likewise, Khecheopalri which contains several aquatic fauna and flora is declared as a sacred lake in Sikkim.

Question 15.
Differentiate between in situ and ex situ conservation. (CBSE Delhi 2011, Sample Paper 2020)
Answer:
Differences between in situ conservation and ex situ conservation:

Question 16.
(i) Explain the ‘Ex situ’ conservation of Biodiversity. How is the In situ conservation different from it? (CBSE Delhi 2018 C)
Answer:

• It is the conservation of endangered species outside their natural habitat.
• Protection from all adverse factors is ensured.
• Offsprings produced in captive breeding are released in natural habitats for acclimatization.

(ii) Which one of the two in situ or ex situ biodiversity conservation measures helps the larger number of species to survive? Explain. (Outside Delhi 2019)
Answer:

1. In situ, biodiversity conservation measures will help the larger number of species to survive.
2. In situ is onsite conservation, i.e. it is the conservation of endangered species in their natural habitat. Whereas ex situ conservation is the conservation of endangered species outside their natural habitat.
3. To conserve species in their natural habitat, the entire ecosystem has to be conserved including all the biotic and abiotic components of the ecosystem that are associated with the target species.
4. In situ conservation helps in the restoration of degraded ecosystems and habitats that are means of conserving genetic resources species ecosystems and landscapes, without uprooting the local people.

Question 17.
Compare the ecological biodiversity existing in India and Norway. (CBSE Outside Delhi 2019)
Answer:
At the ecosystem level, India is far more diverse than the Scandinavian country Norway with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows.

Question 18.
What are Ramsar sites?
Answer:
Ramsar sites are wetlands spread over a wide area. These sites support a wide range of flora and fauna. There are about 25 Ramsar sites in India. Conservation of wetland is the main mission. World wetland day is observed on 2nd February.

Question 19.
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Answer:

1. Earth’s rich biodiversity is vital for indirect benefits like control of floods and soil erosion. Species richness checks soil erosion by binding the soil particles thereby reducing the rate of water velocity, hence reducing the chances of floods.
2. The roots of plants make the soil porous.

Question 20.
The species diversity of plants at 22% is much less than that of animals. What could be the explanation of how animals achieved greater diversification?
Answer:

1. Since plants cannot move from their predators and harsh treatment of environmental conditions, thus have become extinct.
2. As the animals can move away from such conditions, the evolution of favorable characters has taken place in them.

Question 21.
Suggest two practices giving one example of each that helps protects rare or threatened species. (CBSE 2017)
Answer:

1. By using the cryopreservation (preservation at -196°C) technique, sperms, eggs, tissues, and embryos can be stored for long period in gene banks, seed banks, etc.
2. Plants are propagated in vitro using tissue culture methods.

Question 22.
Pollen banks are playing a very important role in promoting plant breeding programs the world over. How are pollens preserved in the pollen banks? Explain. How are such banks benefitting our farmers? Write any two ways. (CBSE Delhi 2019)
Answer:
Preservation of pollen is done in the pollen banks: Pollen grains of a large number of species can be preserved for years in liquid nitrogen at a temperature of -196°C. It is called cryopreservation. Pollen remains viable for a very long duration.

It helps to conserve a large number of species. It can prevent the complete extinction of many species and help to maintain biodiversity.

Question 23.
What is cryopreservation? Mention how it is used in the conversation of biodiversity. (CBSE Outside Delhi 2019)
Answer:
Cryopreservation or cryo conservation is a process where organelles, cells, tissues, extracellular matrix, organs, or any other biological structures are preserved by cooling to very low temperatures, i.e. 196°C in liquid nitrogen.

Role in the conservation of biodiversity: It is an ex-situ method of conservation of biodiversity. Gametes of threatened species are preserved in viable and fertile conditions for long period. They can be used as and when required.

Biodiversity and Conservation Important Extra Questions Long Answer Type

Question 1.
What is biodiversity? Why has it become important recently?
Answer:
Biodiversity: The term biodiversity was coined by W.G. Rosen in 1985. It is the occurrence of different kinds of organisms and the complete range of varieties adapted to different climates, environments, and areas being constituents of food chains and food webs of biotic interrelationships. Biodiversity refers to the totality of genes, species, and ecosystems of a region. Biodiversity differs from place to place.

Significance of biodiversity: As there is a continuous loss of biodiversity due to increasing population, resource consumption, urbanization, and pollution, it is important to conserve it. The basic reason for concern is that biodiversity is being lost even before it attains its size. Loss of biodiversity would check the evolutionary capability of biota to cope up with an environmental loss.

Question 2.
Explain what is meant by species diversity? (CBSE 2010)
Answer:
Species diversity. The diversity includes the whole range of organisms found on earth. The number of identified species worldwide is between 1.7 and 1.8 million. However, the estimates of total known species maybe 50 million. A large number of plant and animal species are yet to be identified. There are many more species present in the tropics.

The two important measures of species diversity are:

1. Species richness: It refers to the number of species per unit area.
2. Species evenness: It refers to the relative abundance with which each species is represented in an area.
3. The variety and number of individuals determine the level of diversity of an ecosystem.
4. The Western Ghats have a greater diversity of amphibian species than the Eastern Ghats.

Question 3.
What is genetic diversity? Explain. (CBSE 2010)
Answer:
Genetic diversity:

1. The greater the genetic diversity among organisms of a species, the more sustenance it has against environmental perturbations. The genetically uniform populations are highly prone to diseases and harsh environments.
2. The genetic variation shown by Rauwolfia can be in terms of the concentration and potency of the chemical reserpine.
   There are more than 50,000 genetically different strains of rice and 1,000 varieties of mango in India.

Question 4.
Describe the ecological role of biodiversity.
Answer:
The ecological role of biodiversity:

1. Biodiversity provides plant pollinators, predators, decomposers and contributes to soil fertility.
2. It helps in the purification of air and water, management of flood, drought, and other environmental disasters,
3. Ecosystems with more diversity can withstand the environmental challenges better because genetically diverse species present in the ecosystem will have different tolerance ranges for a given environmental stress, hence they cannot be easily eliminated by any single stress at a time. However, if the ecosystem contains only a few species, it will become a fragile or unstable ecosystem.
4. The species with high genetic diversity and the ecosystems with high biodiversity have a greater capacity for adaptation against environmental perturbations.

Question 5.
Write a short note on three perspectives of community and ecosystem level of diversity.
Answer:
The three perspectives of diversity at the level of community and ecosystem are:

1. Alpha diversity
2. Beta diversity and
3. Gamma diversity.

1. Alpha diversity: It refers to the diversity of organisms sharing the same community. It has been found that there is an increase in diversity with a decrease in latitude.

2. Beta diversity: The rate of replacement of species along a gradient of habitat or communities is called beta diversity.

3. Gamma diversity: It is the rate at which additional species are found as a replacement in different localities of the same habitat.

Question 6.
Give an account of global biodiversity.
Answer:
Global biodiversity:
1. According to IUCN (2004), the total number of plant and animal species described is about 1.5 million. The species inventories for taxonomic groups in temperate countries/ regions are more complete than those in tropical countries/regions.

2. A more conservative and scientifically sound estimate has been made by Robert May; it puts the global species diversity at about seven million. More than 70% of all the species recorded are animals and plants account for about 22%; 70% of the animals are insects.

These estimates do not give any figure for prokaryotes for the following reasons:

• The conventional taxonomic methods are not suitable/sufficient for identifying these microbial species,
• Many of these species cannot be cultured under laboratory conditions.
• Biochemical and molecular biology techniques would put their diversity into millions.

Question 7.
Describe the species-area relationship.
Answer:
Species-Area relationship
Alexander Von Humboldt has observed that within a region, species richness increased with the increased explored area, but only up to a limit.

The relationship between species richness and area for a number of taxa like angiosperms plants, freshwater fishes, and birds is found to be a rectangular hyperbola.

On a log scale, the relationship becomes linear (straight line) and is described by the equation.
Species area relationship

log S = log C + Z log A, where,
S = Species Richness
Z = Slope of the line (regression coefficient)
A = area and
C = y-intercept Ecologists have found out that the value of the Z-line ranges between 0.1 and 0.2 irrespective of the taxonomic group or the region.

But this analysis in very large areas like a continent, the Z value ranges between 0.6 and 1.2. The Z value for frugivorous birds and mammals in the tropical forests is found to be 1.15.

Question 8.
What kinds of threats to biodiversity may lead to its loss?
Answer:
Threats to biodiversity:

1. Habitat loss. In order to utilize the resources there occurs the destruction of habitat.
2. Disturbance and pollution. A large number of organisms are destroyed due to natural disturbances such as fire, tree fall, defoliation by insects. Man’s activities are causing pollution.
3. Introduction of exotic species. The introduction of new species into an area causes disturbances that may lead to the disappearance of native species.
4. The extinction of species is a natural process.

Question 9.
Give a brief account of the loss of biodiversity at the global level.
Answer:
The colonization of the tropical Pacific Islands by human beings has led to the extinction of more than two thousand species of native birds.

IUCN red list (2004) documents the extinction of 784 species in the last 500 years that include 359 invertebrates, 338 vertebrates, and 87 plants.

Some of the animals that have become extinct in recent times are given below:

1. Steller’s sea cow (Russia)
2. Dodo (Mauritius)
3. Thylacine (Australia)
4. Quagga (Africa)
5. Three subspecies (Bali, Javan, Caspian) of the tiger.
6. 27 species have become extinct in the last twenty years alone.
7. Amphibians are more vulnerable to extinction.

Though about 15,5000 species are facing extinction, at present following the face the threat of extinction:

• 31% of gymnosperms
• 32% of amphibians
• 12% of bird species
• 23% of mammals

Since the origin of life on earth and evolution, three have been five episodes of mass extinction, but the current rate of extinction is 100-1000 times faster than them, due to human activities.

Question 10.
Write an explanatory note on the efforts for the conservation of biodiversity in India.
Answer:
Conservation of biodiversity in India:

1. In situ conservation is carried out through biosphere reserves, national parks and wildlife sanctuaries, and other protected areas by the Ministry of Environment and Forest reserve.
2. The National Bureau of Plants, Animals, and Fish Genetic Resources collects, conserves and stores germplasms of plants and animals in seed gene banks or field gene banks.
3. Botanical Gardens and Zoological Parks have a large collection of plant and animal species.

Question 11.
Explain the following:
(a) IUCN Red List
Answer:
IUCN Red List: It is a catalog of taxa that are facing the risk of extinction.

The uses of the red list are:

• developing awareness about the threat of loss of biodiversity
• identification and documentation of endangered species
• providing a global index of the decline of biodiversity
• defining conservation.

IUCN has recognized eight red list categories of species.
They are:

1. Extinct
2. Extinct in wild
3. Critically endangered
4. Endangered
5. Vulnerable
6. Lower risk
7. Data deficient and
8. Not evaluated.

The 2000 red list contains an assessment of more than 18,000 species, 11,000 of which are threatened.

(b) Protected areas.
Answer:
Protected areas: These areas are land or sea and are dedicated to the protection and maintenance of biological diversity. They include National Parks, Sanctuaries, and Biosphere reserves. As of September 2002, India has 581 protected areas.

National parks: A national park is an area that is strictly reserved for the betterment of the wildlife and where activities like forestry, grazing, or cultivation are not permitted. In these parks, even private ownership rights are not allowed. Sanctuaries. A sanctuary is a protected area that is reserved for the conservation of only animals and human activities like harvesting of timber, collection of minor forest products and private ownership is allowed so long as they do not interfere with the well-being of animals.

A biosphere reserve is a specified area in which multiple uses of the land are permitted by dividing it into certain zones, each zone is specified for a particular activity.

Question 12.
What is a biosphere reserve? Show the zonation of the biosphere reserve.
Answer:
Biosphere Reserves. Biosphere reserves are a special category of protected areas of land and/or coastal environments, wherein people are an integral component of the system. These are representative examples of natural biomes and contain unique biological communities.

The zonation in a terrestrial Biosphere Reserve

Question 13.
Show the in situ and ex situ approaches of conserving biodiversity in India.
Answer:

The In situ and ex situ approaches of conserving biodiversity in India.

Question 14.
Write critical notes on the following:
1. Hot spots of biodiversity.
2. Ex-situ conservation.
3. India’s effort in biodiversity. (CBSE Delhi 2019)
Or
States any two criteria for determines biodiversity hotspots. Name any two hotspots of India. (CBSE Sample Paper 2020)
Answer:
1. Hot spots of biodiversity: The concept of ‘Hotspots’ was developed by Norman Myers (1988) to designate specific areas for in situ conservation. The hotspots are the richest and most threatened reservoirs of plant and animal life on earth.

The criteria for determining hotspots are:
(a) Number of endemic species.
(b) Degree of threat which is measured in terms of habitat loss.

There are 25 hotspots in the world out of which two are in India. They are the Western Ghats and Eastern Himalayas.

Hotspot of Eastern Himalayas is active centers of evolution and rich in diversity of flowering angiosperms. The Western Ghats have semi-evergreen forests.

The Western Ghats include two main centers of biodiversity:

• Aqastyamatai hills
• Silent valley.

2. Ex-situ conservation: It means maintenance of off-site collections either in gardens by farmers, botanical garden or storing seeds, genes, pollen, tissue culture, etc. The rare plants have been found to flourish in large numbers under the care and protection of gardeners and nature lovers.

The farmers have been maintaining genetic diversity (enormous varieties) of crop plants since ancient times by saving seeds or other components for the next plantings.

Collection of samples of cultivated and wild varieties of plants and storing them in botanical gardens is another method of conservation of germplasm.

In seeds, the living material remains in a metabolically suspended state. When the seeds are to be stored for longer periods, it is necessary to avoid conditions that favor respiration and enzymatic action.

Advantages of ex situ conservation:

• Threatened and endangered species can be conserved.
• Genetic strains of commercially important plants can be preserved for a long time (seed banks).
• Gametes of threatened species can be preserved in viable and fertile conditions for a longer duration by the cryopreservation technique.
• Loss of biodiversity can be reduced.
• Eggs can be fertilized in-vitro.
• Can conserve a large number of species and the aesthetic value.

3. India’s effort in biodiversity conservation: India has greatly contributed to the conservation of biodiversity owing to its great utility and need for conservation.

The following measures have been taken for this purpose:
(a) Setting up of bodies like Indian Board for Wildlife, Bombay Natural History Society, etc.
(b) Observation of the first week of October as national wildlife week.
(c) introduction of the Wildlife Protection Act in 1972.
(d) Setting up of sanctuaries, national parks, and biosphere reserves.

Question 15.
(i) Why should we conserve biodiversity?
Answer:
We should conserve biodiversity for the following reasons:
(a) Narrow utilitarian arguments Human beings draw direct economic benefits from nature like food, firewood, fiber, construction materials, industrial products, medicines, etc.

(b) Broadly utilitarian arguments. Biodiversity plays a major role in maintaining and sustaining the supply of goods and services

• Amazon forests provide 20% of the oxygen present in the atmosphere.
• The ecosystem provides pollinators.

(c) Ethical reasons. Every organism has intrinsic value even if there is no economic value. Conservation of biodiversity.

(ii) Explain the importance of biodiversity hotspots and sacred groves. (CBSE Delhi 2016)
Answer:
Importance of biodiversity hotspots and sacred groves They provide protection of species richness and a high degree of endemism in natural habitat. Hotspots are regions of the high level of species in their natural habitat. Sacred groves are forest tracts set aside and all trees and wildlife within the area are given total protection.

Question 16.
What is the ES Nino effect? Explain how it accounts for biodiversity loss. (CBSE Delhi 2011)
Answer:
1. El Nino: It is an abnormal warming of surface ocean waters in the eastern tropical Pacific. It is called the Southern Oscillation. The Southern Oscillation is the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific.

When the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice versa. Because ocean warming and pressure reversals are, for the most part, simultaneous, scientists call this phenomenon the El Nino/Southern Oscillation or ENSO for short.

El Nino Effect
Unfortunately not all El Ninos are the same nor does the atmosphere always react in the same way from one El Nino to another. This is why NASA’s Earth scientists continue to take part in international efforts to understand El Nino events. Hopefully, one day scientists will be able to provide sufficient warning so that we can be better prepared to deal with the damages and changes that El Nino causes in the weather.

Question 17.
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it? (CBSE Delhi 2011)
Answer:

1. Human effort to eradicate disease-causing organisms (Poliovirus).
2. This situation may appear when alien species are introduced unintentionally or deliberately into an area. Some of them may become invasive and cause damage to indigenous species.
3. Example: Nile perch introduced into lake Victoria in East Africa led to the extinction of 200 species of cichlid fish in the lake. The introduction of African catfish Clarias gariepinus for aquaculture is threatening the indigenous catfishes in rivers of India.

Question 18.
Explain biodiversity as sources of food and improved varieties.
Or
State the uses of biodiversity in modern agriculture. (CBSE 2011)
Answer:
Use of biodiversity in agriculture:

• As a source of new crops.
• As source material for breeding varieties.
• As a source of new biodegradable pesticides.

Only 20% of total plant species are cultivated to produce 85% of the world’s food.

Wheat, corn, and rice, the three major carbohydrate crops, yield nearly two-third of the food sustaining the human population. Fats, oils, fibers, etc. are other uses for which more and more new species need to be investigated.

Question 19.
(i) “India has a greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.
Answer:
Yes. I agree with the statement. India has greater ecosystem diversity than Norway because it has deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows.

(ii) Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organization. (CBSE 2018)
Answer:
Genetic diversity:

1. Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species.
2. A single species might show high diversity at the genetic level, e.g. Man: Chinese, Indian American, African, etc. India has more than 50,0 genetically different strains of rice and 1,000 varieties of mango.
3. Genetic diversity allows species to adapt to changing environments. This diversity aims to ensure that some species survive drastic changes and thus carry on desirable genes.

Specific diversity:

1. Specific diversity is the ratio of one species population over a total number of organisms across all species in the given biome. ‘Zero’ would be infinite diversity, and ‘one’ represents only one species present.
2. Species diversity is a measure of the diversity within an ecological community that incorporates both species richness, i.e. the number of species in a community and the evenness of species.

Question 20.
Give the approximate numbers of species that have been described and identified all over the world.
Answer:
An approximate number of species that have been described and identified from all over the World:

Question 21.
Give an account of latitudinal gradients of biodiversity.
Answer:
Latitudinal gradients of biodiversity:

1. Species diversity decreases from the equator towards the poles.
2. The tropics (between 23.5°N to 23.5°S) harbor more species than temperate and polar regions.
3. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. There are more than 2,00,000 species in India of which several are confined to India (endemic).
4. For example, Columbia situated near the equator has about 1400 species of birds, while Hew York (41 °N) has 105 species, Greenland (70°N) has about 56 species and India (in the equator region) has 1200 species.
5. The number of species of vascular plants in the tropics is about ten times more than that of temperate forests.
6. The Amazonian rain forest in South America has the greatest biodiversity on earth; it harbors about 40,000 species of plants, 1,25,0 species of insects, 3000 fishes, 427 amphibians, 378 reptiles, 1300 birds, and 427 mammals.

Question 22.
Discuss the characteristics of India’s biodiversity.
Answer:
Characteristics of India’s biodiversity. Biodiversity is not uniformly distributed in space and time. It is rich in tropics.

India’s biodiversity is characterized by the following:
1. India contains 10 bio-geographic regions which include the Himalayan, Trans-Himalayan, the Indian desert, the Semi-arid zone, the Western Ghats, the Deccan Peninsula, the Gangetic Plain, North-East India, and the Islands and Coasts which possess different biodiversity levels.

2. India is one of the world’s 12 leading biodiversity centers of the origin of cultivated plants.

3. Though India has only 2.4% of the land area of the world, it has 8.1% of the global species biodiversity.

4. There are about 45,000 species of plants and 90,000-1,00,000 species of animals; many more species are yet to be discovered and named.

5. If we apply Robert May’s global estimate that only 22% of the total species have been recorded, India probably has more than 1,00,000 species of plants and 3,00,000 species of animals to be discovered and described.

6. India has five natural world heritage sites, 14 biosphere reserves, 89 national parks, 492 wildlife sanctuaries, and 2 hotspots. Heritage sites are places that attract tourists.

7. About 33 percent of the country’s recorded flora are endemic to India and concentrated in the North-East, Western Ghats, North-West Himalaya, and Andaman and Nicobar islands.

Question 23.
(a) List any two ways biodiversity loss affects any region.
Answer:
Effects of biodiversity loss:

1. The decline in plant production
2. Lowered resistance to environmental perturbations such as drought
3. Increased variability in certain ecosystem processes.

(b) Explain any two causes of biodiversity loss, with the help of suitable examples. (CBSE Outside Delhi 2019)
Answer:
Causes of loss of biodiversity:
(A) Habitat fragmentation:

1. Habitat loss and fragmentation create barriers that limit the potential of species to disperse and colonize new areas.
2. Species get divided into smaller populations that are unable to sustain themselves.
3. Migratory birds lose their seasonal habitats.
4. It increases edge areas thus making the species more vulnerable to predators as well as wind and fire.

Thus there is the loss of biodiversity because a large number of animals, e.g. elephants, lions, bears, and large cats require big territories to move around and live in. Likewise, some birds reproduce successfully only in deep forests.

(B) Introduction of exotic species leading to endangering the species Exotic species are having a large impact especially in the island ecosystem, which harbor much of the world’s threatened biodiversity.

A few examples are:

1. Nile perch, an exotic predatory fish introduced into Lake Victoria (South African), threatens the entire ecosystem of the lake by eliminating several native species of the small Cichlid fish species that were endemic to this freshwater aquatic system.
2. Water hyacinth clogs rivers and lakes and threatens the survival of many aquatic species in lakes and river flood plains in several tropical countries including India.

Question 24.
List the uses of biodiversity.
Answer:
Uses of biodiversity:

1. As a source of food and improved varieties.
2. As a source of drugs and medicines.
3. Aesthetic and cultural benefits. Examples of aesthetic rewards include ecotourism, bird watching, wildlife, pet-keeping, gardening, etc. Throughout human history, people have related biodiversity to the very existence of the human race through cultural and religious beliefs.
4. Biodiversity is essential for the maintenance and sustainable utilization of goods and services from the ecological systems as well as from individual species.

Question 25.
What are the uses of IUCN Red list categories?
Answer:
Uses of Red list categories:

• Developing awareness about the importance of threatened biodiversity.
• Identification and documentation of endangered species.
• Providing a global index of the decline of biodiversity.
• Defining conservation priorities at the local level and guiding conservation action.

Question 26.
How is the “sixth episode of extinction” of species on earth, now currently in progress, different from the five earlier episodes? What is it due to? Explain the various causes that have brought about this difference.
Answer:
Earth is heading for sixth extinction due to human activities.

Anthropogenic extinction. An increasing number of species are disappearing from the face of the earth due to human activities. This man-made mass extinction represents a very severe depletion of biodiversity, particularly because it is occurring within a short period of time.

It has been estimated at World Conservation Monitoring Centre that about 384 plant species (mostly phanerogams) and 533 animal species (mostly vertebrates) have become extinct since the year 1600. This rate of extinction of species is 1000 to 10,000 times higher than the earlier rate.

A few interesting points of extinction of species noticed are:

• Tropical forests are losing 14,000-40,0 species per year, i.e. at the rate of 2-5 species per hour.
• Near about 50 percent of species may become extinct at the end of the 21st century, if the present rate does not retard.
• Loss of 17,000 endemic plant species and 350,000 endemic animals may take place in the near future from 10 high diversity localities in tropical forests.

It seems that earth is heading for the sixth extinction.

Causes:

• Increase in human population and settlements.
• Hunting.
• ver-exploitation of natural resources.
• Destruction of habitat.

Question 27.
Give three hypotheses for explaining, why tropics show the greatest levels of species richness.
Answer:
The following three hypotheses explain how tropics show the greatest level of species richness:
1. Undisturbance in the tropics: Speciation is usually a function of time, unlike temperate areas subjected to frequent glaciations in the past. This type of disturbance has not occurred or remained relatively undisturbed in tropical latitudes for millions of years. Tropical regions, thus, got a long evolutionary time for species diversification.

2. Constancy in season: In tropical regions, the environment is more constant, less seasonal, and predictable. This is not so in temperate regions. Due to this stability and constancy, niche speciation takes place at a faster rate and leads to species richness.

3. Availability of more solar energy: Due to more availability of solar energy in the tropics, productivity is higher. This contributes indirectly to greater species diversity.

Question 28.
How is biodiversity important for Ecosystem functioning?
Answer:
Importance of biodiversity to the ecosystem:

1. Ecologists believe that communities with more species tend to be more stable than those with fewer species,
2. A stable community has the following attributes.
   (a) It shall not show too many variations in the year-to-year productivity.
   (b) It must be either resistant or resilient to seasonal disturbances.
   (c) It must be resistant also to invasion by alien species.
3. David Tilman had shown through his ecology experiments using outdoor plots the following features.
   (a) The plots with more species showed less year-to-year variation in the total biomass.
   (b) Plots with increased diversity showed higher productivity.
4. It is now realized that species richness and diversity are essential for ecosystem health as well as the survival of the human race on the earth.

Question 29.
What are sacred groves? What is their role in conservation? (CBSE Outside Delhi 2016)
Answer:
Sacred Groves are the secret forest patches around places of worship. They are of great religious value among tribal communities.

In such cases, nature is protected by prevailing religious and cultural traditions. Here tracts of forests are set aside and all plants and animals are venerated and provided with complete protection. Examples of sacred groves are Khasi and Jaintia hills in Meghalaya, Aravali hills in Rajasthan, Western Ghat regions of Karnataka, Maharashtra and Sargiya, Chanda and Bastar areas of M.P. In Sikkim, Khecheopalri lake is declared sacred lake by people, thus protecting the aquatic flora and fauna.

Role in conservation. Many rare and threatened plants have been protected in the sacred groves of Meghalaya. Such areas have been found to be most undisturbed and they are usually surrounded by the most degraded landscapes.

Question 30.
What is Ramsar’s mission? Explain the ‘Wise Use concept’?
Answer:
The Ramsar mission.
The Convention’s mission is “the conservation and wise use of all wetlands through local and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world”.

The Convention uses a broad definition of the types of wetlands covered in its mission, including lakes and rivers, swamps and marshes, wet grasslands and peatlands, oases, estuaries, deltas and tidal flats, near-shore marine areas, mangroves, and coral reefs, and human-made sites such as fish ponds, rice paddies, reservoirs, and salt pans. The Wise Use concept At the center of the Ramsar philosophy is the “wise use” concept.

The wise use of wetlands is defined as “the maintenance of their ecological character, achieved through the implementation of ecosystem approaches, within the context of sustainable development”. “Wise use” therefore has at its heart the conservation and sustainable use of wetlands and their resources, for the benefit of humankind.

Ramsar commitments The Ramsar Contracting Parties, or the Member States, have committed themselves to implement the “three pillars” of the Convention: to designate suitable wetlands for the List of Wetlands of International Importance (“Ramsar List”) and ensure their effective management; to work towards the wise use of all their wetlands through national land-use planning, appropriate policies and legislation, management actions, and public education; and to cooperate internationally concerning transboundary wetlands, shared wetland systems, shared species, and development projects that may affect wetlands.

Question 31.
Sanctuaries are tracts of land where animals are protected from all types of exploitation. Private ownership is permitted. Collection of minor forest products are allowed.
(i) How many sanctuaries are present in India?
Answer:
India has 551 sanctuaries.

(ii) How much land area they cover?
Answer:
3.6% of geographical area.

(iii) Name any three sanctuaries.
Answer:
(a) Keoladeo Ghana Bird Sanctuary, Bharatpur, Rajasthan
(b) Sultanpur Lake Bird Sanctuary, Gurgaon, Haryana
(c) Periyar Sanctuary, Kerala

(iv) List any three human activities which are allowed In sanctuaries.
Answer:
(a) CoLLection of forest products
(b) Harvesting of timber
(C) Tilling of Land
(d) Private ownership of Land.

Question 32.
Make a list of Ramsar Sites In India.
Answer:
A-List of Ramsar sites in India is as following:

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 14 Ecosystem. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 14 Important Extra Questions Ecosystem

Ecosystem Important Extra Questions Very Short Answer Type

Question 1.
What is an ecosystem?
Answer:
Ecosystem. It is a functional unit of nature where living organisms interact among themselves and also with the physical environment.

Question 2.
Who coined the term ecosystem?
Answer:
Sir Arthur Tansley (1935).

Question 3.
Name two major kinds of ecosystems.
Answer:

1. Terrestrial ecosystem.
2. Aquatic ecosystem.

Question 4.
Write three examples of terrestrial ecosystems.
Answer:
Forests, grasslands, and deserts ecosystem.

Question 5.
Give one example of the smallest and another of large-sized ecosystems.
Answer:

1. Pond
2. Forest.

Question 6.
Give three examples of freshwater ecosystems.
Answer:
Ponds, Lakes, and Streams ecosystems.

Question 7.
Name two saltwater ecosystems.
Answer:
Marine and estuaries ecosystems.

Question 8.
Name two man-made ecosystems.
Answer:

1. Spacecrafts
2. Aquarium
3. Crop field.

Question 9.
Write two examples where man has interfered in the ecosystem.
Answer:

1. Cutting of forests
2. Construction of dams.

Question 10.
How do decomposers obtain food?
Answer:
Decomposers release their enzymes into dead and decaying plants and animal remains and absorb the simple inorganic substances.

Question 11.
Give two examples where there is the transfer of matter from terrestrial to the aquatic ecosystem or vice-versa.
Answer:

1. Dropping of leaves of riverbank trees into the water.
2. Terrestrial birds diving into the water to catch fish.

Question 12.
Write the equation that helps in deriving the net primary productivity of an ecosystem. (CBSE Delhi 2013)
Or
How will you calculate net productivity?
Answer:
GPP – R = NPP

Gross primary productivity – Respiratory processes (loss) = Net primary productivity
Or
Net primary productivity = Gross productivity – respiration loss.

Question 13.
Why are green plants not found beyond certain depths in the ocean? (CBSE 2011)
Answer:
The sunlight cannot penetrate beyond certain depths in the ocean.

Question 14.
Why are green algae not likely to be found in the deepest strata of the ocean? (CBSE Outside Delhi 2013)
Answer:
Green algae are not likely to be found in the deepest strata of the sea because the environment is perpetually dark and the sun as a source of energy is not available.

Question 15.
Name two aquatic ecosystems which have a rich diversity of macrophytes.
Answer:
Wetlands and lakes.

Question 16.
Name two structural features of the ecosystem.
Answer:

1. Species composition
2. Stratification.

Question 17.
How does the standing state of nutrients differ?
Answer:
The standing state of nutrients differs from one ecosystem to another or with the season in the same ecosystem.

Question 18.
Define detritus.
Answer:
Dead plant and animal remains are called detritus.

Question 19.
Name above ground and below ground detritus.
Answer:

1. Dried plant parts and dead animals.
2. Dead roots (root detritus).

Question 20.
What is nutrient immobilization?
Answer:
Soil nutrient gets tied up with biomass of microbes and is not available for other organisms.

Ecosystem Important Extra Questions Very Short Answer Type

Question 1.
List the abiotic components of an ecosystem.
Answer:
The abiotic components of an ecosystem are of four types:

1. Inorganic substances like C, N₂, O₂, C0₂, H₂0, etc.;
2. Organic compounds like carbohydrates, proteins lipids, etc.;
3. Climatic factors (including temperature, light, wind, gases, humidity, rain, and water) (also wave action, water currents),
4. the edaphic factor which includes soil.

Question 2.
List the differences between biotic and abiotic components of the ecosystem.
Answer:
Differences between Biotic and Abiotic Components of the ecosystem:

Question 3.
List the kinds of ecosystems.
Answer:
An ecosystem can be as small as an aquarium in the house or as big as an ocean. The biotic community is spread everywhere. Land, water, and air show the presence of living things.

The major ecosystems of the world are:

Question 4.
Show the processes involved in the decomposition of detritus.
Or
Describe the process of decomposition of detritus under the following heads: Fragmentation, Leaching, Catabolism, Humification, and Mineralisation. (CBSE 2010)
Answer:
Process of decomposition:

Processes involved in the decomposition of detritus

1. Fragmentation: Detrivores break down detritus in small particles.
2. Leaching: Water-soluble inorganic nutrients seep inside the soil and get precipitated as unavailable salt.
3. Catabolism: Here, bacteria and fungus degrade detritus by their enzymes into simple inorganic ions.
4. Humification: Formation of hummus at a slow rate.
5. Mineralization: Release of minerals from humus by microbes.

Question 5.
What are the functions of the ecosystem?
Answer:
Functions of the ecosystem. Ecosystems possess a natural tendency to persist. This is made possible by a variety of functions (activities undertaken to ensure persistence) performed by the structural components.

The key functions of the ecosystem are:

• Productivity;
• Energy flow;
• Nutrient cycling;
• Decomposition

Question 6.
What is a food chain? List the kinds of food chains.
Answer:
Food Chain: A nutritive interaction among biotic communities (organisms) involving a producer, various levels of consumers, and a decomposer forms a food chain. Each step in a food chain is called a trophic level. Kinds of the food chain. There are 3 kinds of food chains: predator, parasitic and saprophytic chains.

Question 7.
In relation to energy transfer in the ecosystem, explain the statement “10 kg of deer’s meat is equivalent to 1 kg of lion’s flesh”.
Answer:
Passage of food energy from lower trophic level to higher trophic level follows 10% law. 10% law states that only 10% of total energy is transmitted from one trophic level to another. The rest of the energy is dissipated. A lion feeds on deer (lower trophic level). So 10 kg of meat of deer will form only 1 kg of lion’s flesh. The rest of the food energy present in deer meat is wasted and dissipated.

Question 8.
Primary productivity varies from ecosystem to ecosystem. Explain.
Answer:
Primary productivity depends upon the producers (plant species), their photosynthetic potential, soil, climate, and other environmental factors of an ecosystem. They are seldom similar in different ecosystems. Therefore, primary productivity varies from ecosystem to ecosystem.

Question 9.
What is an incomplete ecosystem? Explain with the help of a suitable example.
Answer:
An ecosystem comprises biotic and abiotic components. Abiotic components include light, air, water, temperature, humidity, etc., while biotic factor comprises all living organisms. The absence or limited availability of any component (either abiotic or biotic) makes an ecosystem incomplete like the profundal and benthic zones in an aquatic ecosystem.

Question 10.
What are the shortcomings of ecological pyramids in the study of ecosystems?
Answer:
Ecological pyramids are the graphical representation of ecological parameters. These are characterized by a pyramid of the number, the pyramid of mass, and the pyramid of energy in an ecosystem. The assumption of a simple food chain is the major shortcoming of ecological pyramids.

If we do not provide a food web, a clear position of the trophic levels of an organism cannot be given. Saprophytic organisms are not given any place in the ecological pyramid, though they are an important component in an ecosystem.

Question 11.
Write a note on secondary productivity.
Answer:
Secondary productivity. It refers to synthesized biomass at different trophic levels beginning from primary consumer level to top-level carnivores. At each consumer level, a part of the energy is used for respiration and a part of it is stored. If there is more storage than consumption, the biomass of the population would be higher at the end of a time period than at the beginning. This rate of increase in biomass of heterotrophs is called secondary productivity.

Question 12.
Sketch Pyramid of energy. Why is pyramid energy upright? (CBSE Delhi 2019 C)
Answer:
A pyramid of energy is always upright: It is a graphic representation of energy, amount of energy trapped per unit time, and area in different trophic levels of a food chain with producers forming the base and top consumer at the top.

An ideal pyramid of energy. Observe that primary producers convert only 1% of the energy from the sunlight available to them into NPP.

There is the unidirectional flow of energy in a food chain. As the energy passes from one trophic level to a higher trophic level along the food chain, its amount decreases. So, the pyramid of energy is always upright.

Question 13.
Construct a pyramid of biomass starting with phytoplankton. Label its three trophic levels. Is the pyramid upright or inverted? Justify your answer. (CBSE Sample Paper 2020)
Answer:
A pyramid of biomass is an aquatic ecosys¬tem and is always inverted. The biomass of primary producer (PP) phytoplankton is smaller than the biomass of zooplankton. The latter constitute primary consumers (PC). The biomass of carnivores, i.e. fish, a secondary consumer (SC), is more than the biomass of the primary consumer. So the pyramid of the biomass of the aquatic ecosystem is inverted.

Pyramid of biomass

Question 14.
What is eco-succession? Write its kinds and pattern.
Answer:
A continuous change in a biotic community is called biotic or eco-succession. A stage of climax is also achieved in the process of succession. Succession is of two types primary and secondary. The pattern of succession in any community is decided by pre-existing conditions of that place.

Three kinds of patterns have been observed:

1. Xerosere,
2. Hydrosere and
3. Merosere.

Question 15.
What are the causes of ecological succession?
Answer:

• Biotic and physiographic factors operating simultaneously are the causes of ecological succession.
• Biotic factors, direct succession, and physiographic factors include the climate and other physical factors such as erosion of hills, filling up of lakes and streams.

Question 16.
Give a generalized mode of ecosystem nutrient cycling.
Answer:
A generalized model of ecosystem nutrient cycling:

A generalized model of ecosystem nutrient cycling: Nutrients are brought in (input), moved out (output), and cycled internally in the ecosystem. Boxes represent ecosystem components and arrows show the pathways of nutrient transfers.

Question 17.
Where would you look for signs of secondary succession? When does secondary succession end?
Answer:
Secondary succession occurs where an early community has been damaged leaving a few organisms and considerable organic matter. A destroyed grassland, destroyed forest, or destroyed area by fire or floods will be the site for secondary succession. The development of climax forests marks the end of secondary succession. A destroyed grassland takes 50 to 100 years to recuperate and a destroyed forest takes 200 years to fully recover.

Question 18.
Name the pioneer and the climax species in a waterbody. Mention the changes observed in the biomass and biodiversity of the successive serai communities developing in the waterbody. (CBSE 2009)
Answer:

1. Pioneer communities are the small phytoplankton, which is replaced with time by rooted-submerged plants, rooted-floating angiosperms followed by free-floating plants, then reed swamp, marsh-meadow, scrub, and finally the trees.
2. The climax again is forest.

Ecosystem Important Extra Questions Long Answer Type

Question 1.
What is an ecosystem? Write its main components.
Answer:
Ecosystem. A stable, self-supporting ecological unit resulting from an interaction between a biotic community (living organisms) and its abiotic environment is called an ecosystem.

An ecosystem comprises two main components:

1. biotic including plants, animals, and microorganisms and
2. abiotic mainly including substratum, water, minerals, temperature, carbon dioxide, and oxygen. It must also receive a constant supply of energy (light).

Question 2.
Briefly describe the biotic components of an ecosystem.
Answer:
Biotic components: Of an ecosystem’s biotic components, the plants are producers as they introduce food materials and energy into the living world. The animals are consumers because they get food and energy by consuming plants directly thus called primary consumers (herbivores); secondary/ tertiary consumers (carnivores) obtain energy and food indirectly from plants, and microorganisms are decomposers for they flourish by breaking dead organic matter to simple substances that are returned to environment for reuse by plants.

In an ecosystem, nutrients are used again and again in a cyclic manner, whereas energy trapped from sunlight is lost as heat.

Question 3.
Give an account of factors affecting the rate of decomposition.
Answer:
Factors affecting decomposition:

1. The upper layer of soil is the main site of decomposition processes in the ecosystem.
2. The rate of decomposition of detritus is affected by climatic factors and the chemical quality of detritus.
3. Temperature and soil moisture affect the activities of root microbes.
4. The chemical quality of detritus is determined by the relative proportion of water-soluble substances, polyphenols, lignin, and nitrogen.

Question 4.
List the important differences between producers and decomposers.
Answer:
Differences between producers and decomposers:

Question 5.
Explain the terms standing crop, biomass, and standing state.
Or
State what does a standing crop of a trophic level represent? (CBSE Outside Delhi 2013)
Answer:
Standing crop: Each trophic level has a certain mass of living material at a particular time called the standing crop. Biomass. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate as the moisture content of biomass fluctuates greatly.

Standing State: Organisms need a constant supply of nutrients to grow, reproduce and regulate various body functions. The amount of nutrients, such as carbon, nitrogen, phosphorus, calcium, etc. present in the soil at any given time, is referred to as the standing state. It varies in different kinds of ecosystems and also on a seasonal basis.

Question 6.
Give a diagrammatic representation of trophic levels in an ecosystem.
Answer:

Diagrammatic representation of trophic levels in an ecosystem.

Question 7.
Sometimes due to biotic/abiotic factors, the climax remains in a particular serai stage (pre-climax) without reaching climax. Do you agree with this statement? If yes give a suitable example.
Answer:
Sometimes pre-climax stage remains in a particular serai stage without reaching the climax because during ecological succession any change in abiotic and biotic components may affect the particular serai stage, leading to the pre-climax stage before the climax is achieved.

This type of condition occurs in the presence of seeds and other propagules. This secondarily based area may be invaded by moss or exotic weeds thus exhibiting succession seriously and the climax community is never regenerated.

Question 8.
Explain the meaning of the food web and illustrate with a ray diagram.
Answer:
Food web. In nature, the food chains are not strictly linear, but are interrelated and interconnected with one another. Generally, the various food chains in a community are so interlinked as to form a sort of web. As a result, one animal may be a link in more than one food chain.

A network of food chains in a community is referred to as a food web. A food web may have all or some of the three types of food chains, i.e. detritus, predator, and parasitic. The food webs become more complicated because of the variability of taste and preference, availability and compulsion, and several other factors at each level. For example, tigers normally do not eat fish or crab, but they are forced to feed on them in the Sundarbans.

Question 9.
Starting from a bare rock or a site of volcanic eruption, trace the organisms that participate in the process of succession. (CBSE Delhi 2011)
Or
Describe the process of succession on a base rock. (CBSE 2012)
Answer:

1. Simple organisms appear first of all on such an exposed site as lichens. Lichens make conditions suitable for mosses (bryophytes).
2. Gradually a variety of complex organisms join the community.
   Stages of biotic succession.
3. Finally, large plants, trees, etc. appeared. It can be illustrated that lichens are pioneers, followed by mosses, annual grasses, perennial herbs, shrubs, and finally trees along with their characteristic animal populations.

Question 10.
How does succession differ in terrestrial and aquatic systems? Give salient points. (CBSE Delhi 2019)
Answer:
Differences between terrestrial and aquatic succession:

Question 11.
Explain the difference between the serai stage and climax community during succession.
Answer:
Change during succession:

Question 12.
(a) Write the pioneer species each of xerarch and Hydr-arch successions. Which type of climax community is attained by both these successions?
Answer:

• Pioneer species of xerarch succession: Wind-borne lichen propagules settle on wet rock soon after rain or heavy dew. Pioneer lichens are crustose lichens. Examples: Graphis, Rhizocarpon.
• Climax stages of xerarch succession: Trees growing in areas occupied by shrubs.
• Pioneer species of Hydr-arch succession: Phytoplankton examples are diatoms, green flagellates, single-celled or filamentous green algae as well as blue-green algae.
• Climax stages of hydra succession: Climax forest of trees

(b) Why is secondary succession faster than primary succession? Explain. (CBSE 2019 C)
Answer:
Secondary succession is faster than primary succession:

• It has a secondarily based area built-in soil organic matter.
• It is biologically fertile.
• Underground parts, some seeds, and remnant species quickly give rise to a new community.

Secondary succession takes 50-100 years to complete in grassland and 100—200 years for the development of the forest. It takes short time as com¬pared to primary succession.

Question 13.
Outline the salient features of the ecosystem nitrogen cycling.
Answer:
Salient features of the ecosystem nitrogen cycle are listed below.

1. The ultimate source of nitrogen is an atmosphere that cannot be directly metabolized by living organisms.
2. Nitrogen-fixing bacterial activities facilitate the entry of nitrogen into biological pathways.
3. Azotobacter and Clostridium are the major free nitrogen-fixing bacteria in the soil.
4. Ammonification is done by many bacteria.
5. Ammonia is converted into nitrate by a group of chemoautotrophic bacteria through a two-step process called nitrification.
6. Denitrifying bacteria transform nitrate nitrogen to nitrous and nitric oxides ultimately to gaseous nitrogen.
7. Most plants absorb nitrate from soil.

Question 14.
List the features of the phosphorus cycle.
Answer:
Features of the phosphorus cycle are listed below.

1. The natural reservoir of phosphorus is a rock in the form of phosphates.
2. Minute quantities of phosphates get dissolved in the soil solution during weathering of rocks.
3. Phosphates enter the plants through their roots and then the food chain.
4. The organic wastes and dead organisms are decomposed by phosphate-solubilizing bacteria, which release phosphorus back into the soil.
5. The atmospheric input of phosphorus through rainfall or gaseous exchange of phosphorus between organisms and the environment is negligible.

Question 15.
“In a food-chain, a trophic level represents a functional level, not a species. Explain.” (CBSE Delhi 2016)
Answer:
In a food chain, a trophic level represents a functional level:

1. Trophic level is a step or division of the food chain. It is characterized by the method of obtaining food.
2. The number of trophic levels is equal to the number of steps in the food chain.
3. The two fundamental trophic levels are producers and consumers.
4. Producers are autotrophic organisms found in the ecosystem which synthesize food from raw materials. There are many such organisms at this level that comprise the first trophic level and not just one species, e.g. green algae plant, phytoplankton, etc.
5. Consumers are heterotrophic organisms. Herbivores are primary consumers. In a pond ecosystem many crustaceans, larvae of insects constitute this trophic level.

Similarly, at the next trophic level, a number of small fishes, not just one species consist of the secondary consumer.

Question 16.
Explain the impact of human activities on the carbon cycle in nature and list its harmful effects. (CBSE Delhi 2019 C)
Answer:
Impact of human activities on the carbon cycle: Carbon is a component of all living organic compounds of protoplasm. It constitutes 49% of dry weight. C0₂ is present in the air. It is dissolved in water as carbonic acid and bicarbonates. It is also present in fossil fuels and graphite in rocks.

There is a regulation of the carbon cycle in nature. Rapid deforestation and the massive burning of fossil fuel for energy and transport have significantly increased the rate of releasing C0₂ into the atmosphere. Harmful effect. Greenhouse effect and global warming.

Question 17.
What are ecosystem services? Briefly explain. (CBSE Delhi 2019)
Answer:
Ecosystem Services. The products of ecosystem processes are named ecosystem services.
Examples:
The following services are provided by the forest ecosystem.
They are:

• purify air,
• mitigate droughts and floods,
• help in the cycling of nutrients,
• provide habitat to a number of the wildlife,
• act as a storehouse of carbon,
• influence the hydrological cycle and
• maintain biodiversity.

The value of services of biodiversity is difficult to determine. Robert Constanza et al. have tried to put price tags on nature’s life-support services. Researchers have estimated them to be 33 trillion US dollars a year, while our global gross production is only 18 trillion US dollars.

Question 18.
What are the two main components of an ecosystem? Describe the physical factors which affect the distribution of organisms in different habitats.
Answer:
Abiotic (physical) and biotic components are the two main components of an ecosystem.
Abiotic components or physical factors:
1. Temperature: The physiological and behavioral adaptations of most animals depend upon the changes in the environmental temperature. The rates of photosynthesis and respiration in plants also fluctuate depending upon the change in temperature.

2. Water: The extent to which an organism is dependent on an abundant water supply depends on its requirements and its ability to conserve it in adverse conditions. Organisms living in dry habitats generally have good water conservation such as in cacti and camels.

3. Light: This is essential for all green plants and photosynthetic bacteria, and for all the animals dependent on the plants.

4. Humidity: This is important because it can affect the rate at which water evaporates from the surface of an organism, which in turn influences its ability to withstand drought.

5. Wind and air currents: This particularly applies to plants. Only plants with strong root systems and tough stems can live in exposed places where winds are fierce. The wind is also instrumental in the dispersal of spores and seeds.

6. pH: This influences the distribution of plants in soil and fresh-water ponds. Some plants thrive in acidic conditions others in neutral or alkaline conditions. Most are highly sensitive to changes in pH.

7. Soil nutrients: These particularly affect the distribution of plants in the soil.

8. Water currents: Particularly in rivers and streams. Only organisms capable of swimming or avoiding strong currents can survive.

9. Topography. Minor topographical differences may be just as important in influencing the distribution of organisms as wide geographical separation.

10. Background. The distribution of organisms whose shape or coloration is such that they are camouflaged when viewed against a particular background is related to the general texture and pattern of the environment.

Question 19.
Name the two fundamental trophic levels and describe the general makeup of each.
Answer:
The two fundamental trophic levels include the following:
1. Producers (Autotrophic organisms): Green plants are the producers in any ecosystem. They also include photosynthetic bacteria. The producers use radiant energy of the Sun during photosynthesis whereby carbon dioxide is assimilated and the light energy is covered into chemical energy.

This energy is locked up into the energy-rich carbon compounds i.e. carbohydrates. The oxygen that is evolved as a by-product in photosynthesis is used in respiration by all living organisms.

2. Consumers (Heterotrophic organisms): They are the living members of the ecosystem which consume the food synthesized by the producers. All living animals are thought to be consumers.

The consumers may be of the following types:
(a) Primary consumers (also called first-order consumers) which are purely herbivorous and depend upon green plants i.e. on producers for their food e.g., Cow, Goat, Rabbit, Deer, Grasshopper, and other insects.
(b) Secondary consumers (also called second-order consumers) are carnivorous animals and eat the flesh of herbivorous animals e.g., Tiger, Lion, Dog, Cat, Frog, etc.
(c) Tertiary consumers are the carnivorous animals that eat other carnivores e.g. Snake eats a frog, birds eat fishes
(d) Top consumers are carnivores of an ecosystem that are not killed and eaten by other animals e.g. Lions, vultures, etc.

Question 20.
Explain the meaning of biotic succession taking an example of succession in a hydrosere.
Answer:
Biotic Succession: The organisms interact among themselves. They not only influence their community but also change their physical or abiotic environment. The alteration in the physical environment is such as to continually favor another set of organisms till a stable community is formed.

Such a biologically controlled modification in the composition of a community of a particular area is called biotic succession or ecological succession. Biotic succession is also known as a successive development of different communities in a particular area till a climax community is formed.

The following seven stages of the hydrosere pattern of succession can be observed:

1. Phytoplanktonic stage (Free-floating angiosperm)
2. Rooted submerged stage
3. Rooted floating stage
4. Amphibian or Reed Swamp stage
5. Sedge meadow stage
6. Woodland stage
7. Forest stage.

Question 21.
Give the graphic representation of the nitrogen cycle.
Answer:

Nitrogen Cycle in Nature.

Question 22.
Distinguish between the following:
(i) Grazing food chain and detritus food chain (CBSE 2008)
Answer:
Differences between grazing food chain and detritus food chain:

(ii) Production and decomposition
Answer:
Differences between production and decomposition:

(iii) Upright and inverted pyramid
Answer:
Differences between Upright pyramid and Inverted pyramid:

(iv) Food chain and food web
Answer:
Differences between food chain and food web:

(v) Litter and detritus
Answer:
Difference between Litter and detritus:

(vi) Primary and secondary productivity.
Answer:
Differences between primary productivity and secondary productivity:

Question 23.
Define ecological pyramid and describe pyramids of number and biomass.
Or
Construct a pyramid of biomass starting with phytoplankton. Label three trophic levels. Is the pyramid upright or inverted? Why? (CBSE 2009)
Answer:
Definition: An ecological pyramid is a graphical/mathematical representation of an ecological parameter, like a number or biomass or accumulated energy at different trophic levels in a food chain in an ecosystem.
1. Pyramid of number: The pyramid is the graphical/mathematical representation of a number of organisms present at each trophic level in a food chain of a particular ecosystem.

When the number of organisms at successive levels are calculated mathematically and plotted, they assume the shape of a pyramid. This is called a pyramid of numbers. The base represents the number of producers whereas the tip is represented by top consumers; inverted pyramids can also be formed.

In the given pyramid of the number, the number of producers (here grass and trees are the producers) will be far more than any other level. The number of consumers will be comparatively less than herbivores. You can guess if the number of carnivores increases and exceeds the herbivores then what the result will be?

The figure shows an inverted pyramid and there you can see producer is one tree and dependents like primary and secondary consumers are many. Parasite insects of birds will be definitely more than the number of birds.

Pyramid of Numbers:
A. Straight—Forest and Water ecosystem
B. Inverted—Tree Ecosystem.
C. SpindLe shaped

2. Pyramid of Biomass: Biomass is defined as the total weight of dry matter present in an ecosystem at a given time. Graphical measurement of biomass is called the pyramid of biomass. Trophic levels at the base represent biomass as numbers in a pyramid of numbers. Here also you can obtain an upright and inverted pyramid.

Pyramid of biomass Upright-Tree and forest ecosys¬tem. Inverted-Aquatic ecosystem.

The aquatic pyramid of biomass is always inverted because the biomass of fishes far exceeds the biomass of phytoplankton.

Question 24.
What is primary productivity? Give a brief description of factors that affect primary productivity. (CBSE Delhi 2011)
Answer:
The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis is called primary productivity.

It is expressed in terms of gm^-2yr^-1 or kcal m^-2yr^-1. Primary productivity depends upon a number of environmental factors like:

1. Availability of nutrients which varies in different types of ecosystem.
2. Photosynthetic capacity of plants.
3. The plant species inhabiting a particular area.
4. Environmental factors.

Question 25.
Define decomposition and describe the processes and products of decomposition.
Answer:
Decomposition is defined as the process by which complex organic compounds are broken down into simpler inorganic substances that can be reutilized by plants for their growth.

Decomposition involves the following processes:

Question 26.
Give an account of energy flow in an ecosystem.
Answer:
Different components for a universal model of energy flow are shown below:
A generated energy flow model of ecosystem-Boxes represent biotic components and the arrows show the pathways of energy transfer

When a herbivore eats a plant, then it digests and oxidizes the ingested food to liberate energy which is equal to that used in synthesizing the organic biomass by the plant. Some of the released energy is lost as heat while only a part of the energy is used in building the biomass of the herbivore, which is called gross secondary productivity.

The same is repeated when the herbivore is eaten by a primary carnivore and so on. At each transfer, about 80-90% of potential energy is dissipated as heat while only 10-20% of energy is available to the next trophic level.

Thus, there is a decline in the amount of energy passing from one trophic level to the next trophic level. The study of energy transfer is called bioenergetics. Secondary productivity tends to be about 10 percent at the herbivore level, although efficiency may be higher, 20 percent at the carnivore level.

So regarding the energy flow, an ecosystem is characterized by the following:

• Unidirectional flow of energy.
• The decrease in useful energy.
• Return of radiant energy of the Sun to the non-living system as heat.

Question 27.
Outline salient features of carbon cycling in an ecosystem. (CBSE Delhi 2012)
Answer:
The reservoirs of carbon are listed below:

1. Carbon dioxide present in the air.
2. Carbon dioxide dissolved in water.
3. Carbonates in the earth’s crust.
4. Fossil fuels like coal and petroleum,
5. Bicarbonates in oceans.

The carbon cycle is the simplest of all nutrient cycles. Its salient features are listed below:
1. CO₂ utilization: Carbon dioxide is used by green plants for the process of photosynthesis, and oxygen is released as a by-product. The fixed carbon enters the food chain and is passed to herbivores, carnivores, and decomposers. About 4 x 1013 kg of carbon is fixed in the biosphere through photosynthesis annually.

Carbon cycle in nature.

2. C0₂ production and return to the atmosphere:
(a) Carbon dioxide is released into the atmosphere by the respiration of producers and consumers.
(b) It is also released by the decomposition of organic wastes and dead bodies by decomposers by the action of bacteria and fungi of decay.
(c) Burning of wood and fossil fuels also releases C0₂ into the atmosphere.
(d) Volcanic eruptions and hot springs also release C02 into the atmosphere.
(e) Weathering of carbonate-containing rocks by the action of acids also adds C0₂ to the atmosphere.

Question 28.
Name the pioneer species on a bare rock. How do they help in establishing the next type of vegetation? Mention the type of climax community that will ultimately get established. (CBSE 2009)
Answer:

1. Lichens and mosses are the pioneer community. Lichens secrete acids which dissolve the rocks and helps in weathering rocks to form soil.
2. Soil is formed by the action of lichens.
3. Invasion is the successful establishment of species.
4. The reaction is most important in succession. It is the mechanism of modification of the environment due to the influence of living organisms. Changes take place; annual grasses, perennial herbs, shrubs, and finally trees appear along with animal communities.
5. Angiosperms trees forming forests will form climax communities.

Question 29.
(i) What is an ecological pyramid? Compare the pyramids of energy, biomass, and numbers.
Answer:
Ecological pyramid: An ecological pyramid is a graphical representation of an ecological parameter, like a number or biomass or accumulated energy at different trophic levels in a food chain in an ecosystem.

Ecological pyramids are of three types:

1. Pyramid of number
2. Pyramid of biomass
3. Pyramid of energy

(ii) Write any two limitations of ecological pyramids. (CBSE 2017)
Answer:
Limitations of ecological pyramids:
(a) Ecological pyramid never takes into account the same species belonging to two or more trophic levels.
(b) It assumes a simple food chain, which never exists in nature.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 13 Organisms and Populations. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 13 Important Extra Questions Organisms and Populations

Organisms and Populations Important Extra Questions Very Short Answer Type

Question 1.
Define microclimate.
Answer:
Microclimate represents the climatic

Question 2.
Define habitat and niche.
Answer:
Habitat is the native environment of conditions that prevail at a local scale or in animal or place. area of limited size. Niche is the position or function of an organism in a community of plants and animals.

Question 3.
How is thermoregulation achieved in polar bears?
Answer:
Thermoregulation in the polar bear. By developing blubber in a subcutaneous zone prevents loss of body heat.

Question 4.
What are osmoconformers? Give one example.
Answer:
Osmoconformers. Animals that can change the osmolarity of their body fluids according to that of the surrounding medium are termed osmoconformers, e.g. Myxine.

Question 5.
What factors cause annual variations in the intensity and duration of temperature?
Answer:

1. Rotation of the earth around the Sun.
2. The tilt of the earth on its axis.

Question 6.
Species that can tolerate a narrow range of temperature are called ………………..
Answer:
Stenothermic.

Question 7.
What are eurythermic species?
Answer:
Species that can tolerate a wide range of temperature variations are called eurythermic.

Question 8.
Species that can tolerate a wide range of salinity are called ……………………
Answer:
Euryhaline.

Question 9.
Define stenohaline species.
Answer:
It is a species that lives within a narrow range of salinity.

Question 10.
Name two factors that cause the formation of major biomes.
Answer:

1. Variation in the intensity and duration of temperature.
2. Variation in precipitation.

Question 11.
What is the main cause of salinity?
Answer:
Salinity is due to the accumulation of soluble minerals on the surface or beneath the surface of the earth.

Question 12.
What does the stratification of community depict?
Answer:
Stratification of a community depicts vertical layering of vegetation.

Question 13.
From where are individual organisms derived?
Answer:
Individual organisms are always derived from pre-existing organisms through the mechanism of reproduction-may be vegetative, asexual or sexual.

Question 14.
List two negative interactions between two species.
Answer:
Parasitism, Predation.

Question 15.
What is the other term for facultative mutualism?
Answer:
Protocooperation.

Question 16.
Name the association in which one species produces a poisonous substance or a change in environmental conditions that is harmful to another species. (CBSE Delhi 2019)
Answer:
Amensalism.

Question 17.
What is mycorrhiza?
Answer:
It is a symbiotic or mutually beneficial association between a fungus and roots of higher plants.

Question 18.
Emergent land plants that can tolerate the salinity of the sea are called ………………..
Answer:
Mangrove plants.

Question 19.
Give an example of a commensal relationship.
Answer:

1. Epiphytes and tree,
2. Remora fish and shark.

Question 20.
Define community periodicity.
Answer:
The recurrence of daily or seasonal or lunar changes in a community is called community periodicity.

Question 21.
Mention any two significant roles predation plays in nature. (CBSE 2008)
Answer:
Role of predators:

1. Transferring energy to a higher trophic level.
2. They keep the prey population under control.

Question 22.
Why is the polar region not a suitable habitat for a tiny hummingbird? (CBSE 2008)
Answer:
Tiny animals like hummingbird have more surface area compared to their volume. So heat loss may occur which will not be good for the tiny bird in polar regions.

In polar regions, only animals with a thick layer of fat below the skin can survive.

Question 23.
Between birds and amphibians which will be able to cope with global warming? Give reason. (CBSE2008)
Answer:
Birds will be able to cope with global warming because they are homeotherms as body temperature remains constant irrespective to change in surroundings.

Question 24.
Which one of the two stenothermal or eurythermal shows a wide range of distribution on the earth? (CBSE 2008)
Answer:
Eurythermal shows a wide range of distribution on the earth because they can tolerate a wide range of temperature.

Question 25.
In a pond, there were 30 Hydrilla plants. Through reproduction 10 new Hydrilla plants were added in a year. Calculate the birth rate of the population. (CBSE 2010)
Answer:
A number of individuals added = 10 per 20 Hydrilla plants.

\frac{10}{30}= 0.33 offspring per hydrilla plant per year.

Question 26.
How is ‘stratification’ represented in a forest ecosystem? (CBSE Outside Delhi 2014)
Answer:
Stratification is a grouping of plants in a forest into two or more well-defined layers depending upon height like tall trees, medium-sized trees, small trees, bushes and herbs. In the rainforest, it is multi-storeyed.

Question 27.
Give an example of an organism that enters ‘diapause’ and why? (CBSE Delhi 2014)
Answer:
Under unfavourable conditions, many zooplanktonic species in lakes and ponds enter a stage of suspended development called diapause.

Organisms and Populations Important Extra Questions Short Answer Type

Question 1.
Certain species of wasps are seen to
frequently visit flowering fig trees. What type of interaction is seen between them and why? (CBSE 2008, 2014)
Answer:

1. Mutualism.
2. Flowers of a fig tree can only be pollinated by wasp species. In return, female wasp visits the fruit of fig as not only an egg-laying site but also uses the developing seed in fruit for nourishing its larvae.

Question 2.
Write a short note on microclimate.
Answer:
Microclimate: It represents the climatic conditions that prevail at a local scale, or in areas of limited size such as the immediate surroundings of plants and animals. Microclimate generally differs from the prevailing regional climatic conditions. For example, in a forest, dense foliage reduces the amount of light reaching the ground. This also results in a changed air temperature profile. The day-time air temperature inside the forests is lower than the outside temperature. Also, the interior of a forest may be more humid than a nearby non-forested area.

Question 3.
What are the effects of organisms on habitat?
Answer:
Effects of organisms on habitat:

1. Excessive growth may lead to the death of the habitat as in the case of water hyacinth- an increase in population had led to the death of Hussain Sagar lake of Hyderabad.
2. The predominance of a predator will reduce the population of prey.
3. Man manipulates the habitat and has affected the forest causing serious problems due to deforestation. More so man has created pollution of air, water and land.

Question 4.
How do you differentiate habitat from the environment?
Answer:
Differences between habitat and environment:

Question 5.
Differentiate microhabitat. between habitat and
Answer:
Differences between habitat and microhabitat:

Question 6.
List the means by which organisms survive at freezing temperatures.
Answer:

1. The animals are usually white or light coloured. The light colouration of animals helps in camouflage with snow and thermal regulation.
2. Animals are thickly coated with fur.
3. Presence of a thick layer of fat below the skin.

Question 7.
Differentiate eurythermal, stenothermal and euryhaline animals.
Answer:
Differences between eurythermal, stenothermal and euryhaline animals:

Question 8.
Explain how is an orchid plant adapted to changes in temperature and humidity.
Answer:
An orchid plant, e.g.Venda, an epiphyte, is a native of tropical forests of India and South Asia.

Its adaptations are:

• Stem stores water and leaves are adapted to keep water in and dryness out.
• Roots of the plant secure their attachment to the bark of the tree and help in the absorption of moisture from humid air or rain.

Question 9.
Why do submerged plants receive weaker illuminations than exposed floating plants in a lake?
Answer:
Because light intensities of stronger illuminations are absorbed by the exposed floating plants of the lake/water-bodies, so only the weaker illuminations reach the submerged, Some light is reflected at the water surface and a part is absorbed by upper layers of water.

Question 10.
Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.
(i) Salvinia
Answer:
Hydrophyte. Because it is not able to tolerate deficiency of water. It is partially or completely submerged.

(ii) Opuntia
Answer:
Xerophyte. Because it prefers a dry and hot climate with low rainfall, thus has succulent leaves.

(iii) Rhizophora
Answer:
Halophyte. Because it grows in a saline habitat.

(iv) Marigifera
Answer:
Mesophyte. Because it prefers areas with high moisture content.

Question 11.
If a freshwater fish is placed in an aquarium containing seawater, will the fish be able to survive? Explain giving reasons. (CBSE Delhi 2015)
Answer:
No, a freshwater fish placed in the aquarium containing sea-water will not be able to survive. Because its body system is adapted to function normally in a narrow range of salinity and it cannot survive in the high salinity of sea-water.

Question 12.
Distinguish between population and community.
Answer:
Differences between population and community:

Question 13.
How does population size increase or decrease?
Answer:

• Population (size/density) increases by birth, hatching, germination and immigration that add individuals.
• Population (size/density) decreases by death and emigration. The population is regulated by food, space, disease, natural calamities and environmental factors.

Question 14.
Differentiate between natality rate and death/mortality rate.
Answer:
Differences between natality rate and mortality rate:

Question 15.
Discuss the role of predators in an ecosystem.
Answer:
Predators are of great importance as they play the following important roles in an ecosystem:

1. They act as ‘conduits’ for energy transfer to higher trophic levels.
2. They keep the prey population under control, which otherwise can reach very high population density and cause an imbalance in the ecosystem,
3. They help in maintaining species diversity in a community by reducing the intensity of competition among the competing prey species.

Question 16.
What is brood parasitism? Give an example.
Answer:
Brood parasitism. It refers to the phenomenon in which one (parasitic) bird species lays its eggs in the nest of another bird species.

Evolution has occurred in such a way that the eggs of the parasitic birds resemble those of the host bird in size, colour, etc. to avoid the host bird detecting the foreign eggs and ejecting them from the nest. Example. Cuckoo birds lay eggs in the nests of crows.

Question 17.
List a few adaptations that parasites have developed. (CBSE Delhi 2019)
Answer:
Parasites have evolved one or more of the following adaptations:

1. Loss of unnecessary sense organs.
2. Presence of hooks/adhesive organs and suckers.
3. Loss of digestive system.
4. High reproductive capacity.
5. Produces antitoxins to counter toxins to the host.

Question 18.
How do parasites harm the host?
Answer:
The parasites harm the host in the following ways:

1. Reduces the survival of the host.
2. Growth and reproductive rates of hosts are reduced.
3. Render the most vulnerable to its predators by making them physically weak.

Question 19.
Justify the statement “Predators and scavengers are markedly different.”
Answer:
Predators feed on another organism, i.e. prey, whereas scavenger feeds on dead animals or an animal killed by another animal. A predator can be a prey also, e.g. a frog eats insects and the frog may be eaten by a snake. But a scavenger such as jackals, hyenas and vultures cannot kill zebra or giraffe or deer but a lion kills them and leaves a part of it to be eaten by such scavengers.

Question 20.
Mention any two significant roles predators play in nature. (CBSE 2008, 2016)
Answer:
Role of predators:

1. Transferring energy to a higher trophic level.
2. Keeping the prey population under control.

Question 21.
How do organisms manage stressful conditions existing in their habitat for a short duration? Explain with the help of one example each. (CBSE (Delhi) 2008)
Answer:
Physiological adaptations allow some organisms to respond quickly to stressful conditions. At high altitude, mountain (altitude) sickness is experienced resulting in nausea, fatigue and heart palpitations. It is due to low atmospheric pressure at high altitude and the body does not receive the proper amount of oxygen. It is accommodated by increasing RBC production, decreasing the binding capacity of haemoglobin and increasing breathing rate.

Question 22.
Explain with the help of an example each of any three ways the ecologists use to measure the population density of different organisms rather than by calculating their absolute number. (CBSE Delhi 2019 C)
Answer:
Method to measure population density: Population density is the number of individuals of a species per unit area or volume.

P_D= N/S

Where N = The no. of the individual in the region
S = No. of the unit area in a region

1. Number of animals per square kilometre
2. Number of trees per hectare
3. A number of phytoplanktons per cubic litre of water. Sometimes the relative densities also serve the purpose, that is

• The number of fish caught per trap is good enough to measure the population of fish.
• Tiger census is based on pug marks and faecal pellets.

Question 23.
Name the interaction in each of the following:
(i) The cuckoo lays her eggs in the crow’s nest.
Answer:
Brood parasitism.

(ii) Orchid grows on a mango tree.
Answer:
Commensalism.

(ii) Ticks live on the skin of dogs.
Answer:
Parasitism.

(iv) Sea anemone is often found on the shell of a hermit crab. (CBSE Delhi 2008)
Answer:
Mutualism.

Question 24.
Name the interaction in each of the following:
(i) Cuscuta growing on a shoe flower plant.
Answer:
Parasitism.

(ii) Mycorrhizae living on the roots of higher plants.
Answer:
Mutualism.

(iii) Clownfish living among the tentacles of a sea anemone.
Answer:
CommensaLism.

(iv) Koel laying its eggs in the crow’s nest. (CBSE Delhi 2011)
Answer:
Brood parasitism.

Question 25.
Name the interaction In each of the following:
(i) Ascaris worms living in the intestine of human.
Answer:
ParasItism

(ii) Suckerfish attached to the shark.
Answer:
Commensalism

(iii) Smaller barnacles disappeared when Balanus dominated the coast of Scotland.
Answer:
Competition

(iv) Wasp pollinating fig inflorescence. (CBSE 2008)
Answer:
Mutualism.

Question 26.
Why do clownfish and sea anemone pair up? What is this relationship called? (CBSE 2012)
Answer:

1. Commensalism,
2. Interaction between sea-anemone that has stinging tentacles and the clownfish that lives among them in which fish gets protection from predators. The anemone does not appear to derive any benefit from the clownfish.

Question 27.
Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples. (CBSE 2012)
Answer:

1. Thick-walled spores of bacteria and fungi help them to overcome unfavourable conditions.
2. Frogs and lizards undergo hibernation during the winter season.
3. Snails and fish undergo aestivation during summer to avoid summer-related problems of heat and desiccation.
4. Species of zooplankton are known to enter a suspended state of development termed-diapause.

Question 28.
A moss plant is unable to complete its life cycle in a dry environment. State reason. (CBSE Delhi 2015)
Answer:

1. Due to the absence of vascular tissue, water and minerals cannot be transported to various parts.
2. Transfer of flagellated antherozooids to oospore of archegonium depends upon water.

Question 29.
Plants that inhabit a rain-forest are not found in wetlands. Explain. (CBSE Delhi 2016)
Answer:
A habitat is a specific place or area or locality having a combination of factors, physical features and barrier where a community resides. In rainforest plants adapt themselves to the specific conditions of their habitat and the characteristics adaptations related to a particular habitat are not found in those plants living in wetland and vice versa. Thus they can not inhabit a new habitat.

Question 30.
Answer:
In certain seasons we sweat profusely while in some other season we shiver. Explain. (CBSE Delhi 2016)
Answer:
Humans are a warm-blooded or homeothermic or endothermal organism. They maintain a fixed body temperature despite changes in the surrounding. The optimum temperature for maximum efficiency of enzymes is 37°C. Thus the human body maintains a body temperature near it.

Homoeostasis is the phenomenon of maintaining a constant internal environment. Thus during heavy exercise or summer, sweating occurs. It helps in cooling the body. During winter, shivering helps in retaining heat within the body.

Question 31.
How did David Tillman show that the “Stability of a community depends on its species richness”? Explain. (Outside Delhi 2019)
Answer:
The stability of a community depends on its species richness. David Tilman’s long-term ecosystem experiments using outdoor plots provided the answer for species richness. Tilman found that plots with more species showed less year-to-year variations in total biomass. He also showed that increased diversity contributed to higher productivity.

Thus he established that the stability of a community depends on its species richness.

Organisms and Populations Important Extra Questions Long Answer Type

Question 1.
(i) “Organisms may be conformers or regulators.” Explain this statement and give one example of each.
(ii) Why are there more conformers than regulators in the animal world? (CBSE 2017)
Or
Human is categorised as ‘regulators’. Explain how they maintain a constant body temperature. (CBSE Outside Delhi 2019)
Answer:
(i) Regulators are organisms that are able to maintain homoeostasis by physiological and behavioural means. All birds and mammals and few lower vertebrate and invertebrate species maintain homoeostasis by thermoregulation and osmoregulation, e.g. birds and mammals.

However, a majority (99%) of animals and nearly all plants cannot maintain a constant internal environment, i. e. their body temperature is not constant. They are conformers, e.g. fishes, frogs, etc.

(ii) There are more conformers than regulators in the animal world because conformers lack the capability to maintain a constant internal environment or homoeostasis. It is limited to birds, mammals and few lower vertebrate and invertebrate species only because it is a very energy-expensive process.

Question 2.
Explain the ecological hierarchy.
Answer:
Ecological hierarchy: It is a series of graded ecological categories.
Characteristics of ecological hierarchy:

1. A biological unit at each level has a specific structure and function.
2. In this hierarchy, smaller biological units coordinate to form the next higher level of organisation.
3. Only the organisms show free existence.
4. Organisms cannot live in isolation.
5. At each level, different units show interdependence.
6. At each level, the unit shows interaction with the physical environment (energy and matter).
7. The biological units are successfully adapted to their environment.

Question 3.
In a seashore, the benthic animals live in sandy, muddy and rocky substrata and accordingly developed the following adaptations.
Find suitable substratum against each adaptation.
(i) Burrowing
Answer:
In a seashore, the benthic animals adapt to their mode of life according to the nature of the seafloor, e.g. Benthic animals become fossorial (burrowing) in the sandy substratum, e.g. tube worm.

(ii) Building cubes
Answer:
Benthic animals build cubes in the muddy substratum.

(iii) Holdfasts/peduncle
Answer:
Benthic animals develop holdfast/ peduncle if the substratum is rocky.

Question 4.
In a pond, we see plants that are free. floating, rooted-submerged, rooted-emergent, rooted with floating leaves. Write the type of plant against the following examples:
(i) Hydrilla
Answer:
Hydrilla is Rooted submerged.

(ii) Typha
Answer:
Typha is Rooted emergent.

(iii) Nymphaea
Answer:
Nymphaea is Rooted with floating leaves.

(iv) Lemna
Answer:
Lemna is Free-floating.

(v) Vallisneria.
Answer:
Vallisneria is Rooted submerged.

Question 5.
Why do all the freshwater organisms have contractile vacuoles whereas the majority of marine organisms lack them?
Answer:
Contractile vacuole helps in maintaining salt and water level called osmoregulation. Because of the cellular environment of a freshwater organism such as Amoeba, Paramecium etc. being hypertonic, the water diffuses inside the cell constantly and gets collected in the contractile vacuole, which squeezes the extra water out of the cell periodically.

While in the case of marine protozoans organisms, this does not occur due to high salt concentration. These organisms live in isotonic conditions in seawater. Thus there is no need for contractile vacuole.

Question 6.
Explain the following terms:
(i) Mimicry
Answer:
Mimicry: It is a phenomenon in which a living organism modifies its form, appearance, structure or behaviour and looks like another living organism or some inanimate (non-living) object so as to defend from its predators, or to increase the chances of capturing the prey.

The individual which shows mimicry is called a mimic, while the animate or inanimate object with which a mimic resembles is called a model. The concept of mimicry was first observed by an English naturalist, Henry Bates (1862 A.D.), so the phenomenon is also called Batesian mimicry.

Types: Mimicry is of three types:
(a) Protective mimicry,
(b) Aggressive mimicry,
(c) Feigning death or Conscious mimicry.

(ii) Acclimatisation
Answer:
Acclimatisation: The gradual physiological adjustment to slowly changing new environmental conditions is known as acclimatisation. If some factors shift beyond the tolerance range, the organism can come to a tolerance range or migrate to acclimatise.

Question 7.
DepIct the temperature-based thermal stratification in lakes.
Answer:
Thermal stratification in Lakes:

Thermal stratification occurs in lakes, the seasonal mixing patterns of a lake are determined by its temperature profile.

Question 8.
1. How does age distribution help in the study of the population?
2. How does an age pyramid, for the human population at a given point of time helps the policymakers in planning the future? (CBSE Delhi 2016)
Or
Draw a stable human age pyramid. (CBSE Outside Delhi 2019)
Answer:
Age distribution (Age composition). The relative abundance of the organisms of various age groups in the population is called the age distribution of the population. With regard to age distribution, there are three kinds of populations:

1. Rapidly growing population. It has a high birth rate and low death rate, so there is more number of young individuals in the population. According to a recent survey, more than 42% of the Indian population consists of children below the age of 14 years, so the Indian population is called the young population.

2. Stationary population: It has equal birth and death rates, so the population shows zero population growth.

3. Declining population. It has a higher death rate than the birth rate, so the population of young members is lower than that of old members.
(a) For the human population, the age pyramids generally show the age distribution of males and females in a combined diagram.
(b) The shape of the age pyramid reflects the growth status of the population. Thus age pyramid for the human population at a given time helps the policymakers in planning for the future.

Question 9.
Discuss life-history traits of an organism that have evolved in relation to the constraints imposed by biotic and abiotic factors in their habitat.
Answer:
According to ecologists, life-history traits of an organism have evolved in relation to the constraints imposed by the biotic and abiotic factors in their habitats.

1. It can be illustrated with vast variations and life history.
2. The evolution of populations aims at improving reproductive fitness or Darwinian fitness to the maximum in their habitats.
3. They evolve towards the most efficient reproductive strategy.
4. Organisms like Pacific Salmon fish and bamboo breed only once in their lifetime.
5. Most birds and mammals breed many times during their lifetime.
6. Oysters and pelagic fishes produce a large number of small-sized offspring.
7. Birds and mammals produce a small number of large-sized offspring.

Question 10.
What is the predator-prey relationship? Give example. (CBSE 2016)
Answer:
Predation. It is an interspecific interaction, where one animal (called predator) kills Organisms and Populations and consumes the other weaker animal (called prey). Herbivores are predators of plants.

Predator-prey relationship. It is a kind of direct food relationship between two species of animals in which larger species, called predator, attacks, kills and feeds on the smaller species, called prey. It was proved by G.F. Gause (1934).

Although predation and competition appear to be very harmful processes, they are essential to keep a check on the size of the population of other species.

Predation is nature’s way of transferring the energy fixed by plants, to higher trophic levels.
Examples:

1. A tiger killing and eating a deer.
2. A snake eating a frog.
3. A sparrow eating a fruit/seed.

Question 11.
Many prey organisms have developed different defence mechanism. Give a few examples.
Answer:
Prey species have developed various defence mechanisms to reduce the impact of predation; some of them are listed below:

1. Certain insect species and frogs have camouflage (cryptic colouration) to avoid detection by their predators.
2. Some animals (e.g. monarch butterfly) are highly distasteful to their predators. This butterfly species accumulates a chemical by feeding on a poisonous weed during its caterpillar stage.
3. Some prey species are poisonous and hence are avoided by predators, e.g. Dart frogs like Phyllobates bicolour and Dendrobats.

Question 12.
“Herbivores are the predators of plants”. Discuss a few defence mechanisms of plants against herbivory.
Or
Write what do phytophagous insects feed on? (CBSE2012)
Answer:
Herbivores are the predators of plants. The problem of predation is more severe for plants than animals as the plants cannot move away from the predators. About 25% of the known insects are phytophagous and feed on the sap and other parts of plants.

Plants have developed certain morphological and chemical defence mechanisms against herbivores; a few of them are listed below:

1. Morphological: Thorns (Bougainvillaea) and spines (Acacia, Cactus, etc.) are the most common morphological means of defence.
2. Chemical: Plants produce and store certain chemicals which function in one or more of the following ways:
   (a) They make the animal feel sick.
   (b) They inhibit them from feeding.
   (c) They interfere with digestion.
   (d) They even directly kill them, e.g. Calotropis produces a highly poisonous glycoside, that is a cardiac poison.
   (e) Nicotine, strychnine, opium, quinine, etc. are the chemicals produced by plants for their defence against herbivores.

Question 13.
What is parasitism? Define parasite and host. What are the kinds of parasite?
Answer:
Parasitism: This is a relationship between two organisms in which one obtains its nourishment from the other and harms it at the same time.

Parasite: The organism which obtains its food from the other without directly killing it is known as a parasite. Parasites are host specific and parasite and host tend to co-evolve.

Host: The second organism which provides food to the parasite is named the host. Endoparasite. The parasite that lives inside the body of the host is known as endoparasite.

Ectoparasite. The parasite lives on the outside of the body of the host, e.g. Leech, Louse, Bedbug.

Question 14.
Define commensalism. Give examples.
Answer:
Commensalism: It is defined as the interspecific interaction where one species is benefitted while the other species is neither benefitted nor harmed.
Examples:

1. Orchids grow as epiphytes on mango or other fruit trees. Orchids are benefitted by getting shelter, while the tree is neither benefitted nor harmed.
2. The clownfish living among sea anemones get protection from their predators, which stay away from the stinging tentacles of the sea anemone.
3. Barnacles growing on the whale are benefitted to move to where food is available.
4. The cattle egrets always forage near where the cattle are grazing. As the cattle animals stir up, the insects are flushed out from the vegetation. The egrets are benefitted from this as otherwise, it might be difficult for the birds to detect and catch the insects.

Question 15.
Differentiate between the following:
(i) Mutualism commensalism.
Answer:
Differences between mutualism and commensalism:

(ii) Commensalism and amensalism.
Answer:
Differences between commensalism and amensalism:

(iii) Predators and parasites.
Answer:
Differences between predators and parasites:

Question 16.
Study the graph given below and answer the questions that follow:

(i) Write the status of food and space in the curves (a) and (b).
Answer:
Food and space are unlimited in the curve (a), while they are limited in the curve (b).

(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population?
Answer:
In the absence of a predator, any species will grow exponentially and show curve (b).

(iii) Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line. (CBSE 2014)
Answer:
The dotted line represents (k). It is carrying capacity.

Question 17.
Explain parasitism and co-evolution with the help of one example of each. (CBSE Outside Delhi 2016)
Answer:

1. Many parasites have evolved to be host-specific. They can live as parasite only in a single species of host.
2. These organisms parasitize in such a way that both the host and the parasite tend to co-evolve; that is if the host evolves a special mechanism for rejecting or resisting the parasite, in such conditions parasite has to evolve a mechanism to counteract and neutralise them, in order to be successful with the same host species.
3. In accordance with their mode of living, parasites evolve special adaptations such as loss of unnecessary sense organs, presence of adhesive organs or sucker so as to cling to the host. It also loses the digestive system. Parasites have a high reproductive capacity.
4. The human liver fluke depends on the intermediate host (a snail and a fish ) to complete the life cycle.
5. The malarial parasite needs a female anopheles mosquito as a vector to spread to other hosts.

Question 18.
(i) In a pond, there were 200 frogs. 40 more were born in the year. Calculate the birth rate of the population.
Answer:
Birth rate = No. of individuals born/ Total no. of individuals = 40/200 = 0.2 = 0.2 frog per year.

(ii) Population in terms of number is not always a necessary parameter to measure population density. Justify with two examples. (CBSE Outside Delhi 2019)
Answer:
To measure population density, the number is not always a necessary parameter.

For example:
(a) If there are 200 Parthenium plants but only a single huge banyan tree with a large canopy, the population density of banyan is low relative to that of Parthenium which amounts to underestimating the enormous role of the banyan in that community. In such cases, the per cent cover or biomass is a more meaningful measure of the population size.
(b) In a dense laboratory culture of a microbial population in a Petri dish, the total number of microbes is again not an easily adaptable measure because as the population is huge, counting is impossible and time¬consuming.

Question 19.
How do organisms which cannot migrate tend to overcome adverse environ¬mental conditions? Explain taking one example each from vertebrates and angiosperms respectively. (CBSE Delhi 2009)
Answer:
Organisms that cannot migrate tend to overcome adverse environmental conditions by developing several methods/ features. For example, some vertebrates escape the stress caused by unfavourable environmental conditions by escaping in time like bears go into hibernation during the winter months.

In angiosperms, seeds and some other vegetative reproductive structures serve as means to tide over periods of stress. They reduce their metabolic activity and go into an inactive, i.e. ‘dormant’, state. They germinate to form new plant when the favourable conditions return.

Question 20.
Explain how tolerance to environmental factors determines the distribution of species.
Answer:
Range of tolerance: Biological species can show a range of tolerance to environmental factors. These factors show variation in their effects and anyone who is present in the least amount may become limiting. The response of an organism to a range of gradient of a single environmental factor such as temperature, sunlight or nutrient concentration forms a bell-shaped curve as shown in the figure.

The response of an organism to a range or gradient of an environmental factor, (temperature, Light, nutrient)

Question 21.
Discuss in detail various adaptations found in plants and animals in snowy winter of polar regions.
Answer:
Adaptations in plant and animals of polar regions:

1. Organisms living in polar regions have to face the severe snowy winter and show entirely different types of adaptations. Animals in polar regions are generally white or tight coloured. This light colouration helps in camouflage and in thermal regulation.
2. During extreme winter they undergo hibernation.
3. Animals eat a lot of food during summer and autumn and store a lot of energy in the form of fat.
4. During hibernation, their metabolic activities are reduced considerably,
5. The plants growing in these regions remain dormant during extreme winter months.
6. They bear narrow leaves, spines, etc. which are shed easily and rapidly,
7. Plants remain dwarf. Trees are usually not found in these regions as they cannot withstand the low temperatures.

Question 22.
How do desert plants prevent loss of water?
Answer:
Xeric adaptations of desert plants:

1. Some xerophytes remain dormant either as seeds or as roots and during rains, they sprout up. It is termed ephemerals, e.g. Cassia, Argemone.
2. Some desert plants develop succulent organs (stems, leaves and roots), e.g. Asparagus, Begonia, Bryophyilum.
3. Presence of extensive root system.
4. Either leaf is absent or small¬sized leaves present to minimise the rate of transpiration.
5. The stomata get sunken to reduce the rate of transpiration.
6. Presence of thick cuticle on stem and leaf surfaces. This reduces the rate of transpiration.
7. Shedding of leaves in some desert plants. This helps in reducing the surface area and water loss.

Question 23.
(i) What is the competition?
Answer:
Competition is an interaction between organisms for life requirements (nutrition, shelter, sunlight, etc.). It is of two types: intraspecific and interspecific. The effort of a tiger and a leopard for prey is an interspecific competition. In general, it is believed that competition occurs among closely related species when they compete for the same resources that are limited.

(ii) Why is it not true always?
Answer:
But it is found to be not true always for the following reasons:
(a) Completely unrelated species can also compete for the same sources. For example in certain shallow lakes of South America, the visiting flamingoes and the native fishes compete for the same zooplankton as their food.

(b) Resources need not be limiting for the competition to occur, the feeding efficiency of one species might be reduced due to the interfering and inhibitory presence of the other species, even if resources are plenty.

For example, the Abingdon tortoise in Galapagos island became extinct within a decade after goats were introduced into the island: this was due to the fact that the goats had greater browsing efficiency than the tortoise.

(iii) Explain competitive release and Gause’s competitive exclusion principle.
Answer:
Another evidence for the competition is competitive release, a phenomenon in which a species whose distribution is restricted to a small geographical area due to the presence of a competitively superior species, expands its distributional range when the competing species is experimentally removed.

Gause’s competitive exclusion principle states that two closely related species competing for the same resources cannot exist together as the competitively inferior one will be eliminated, but this is true only when the resources are limiting and not otherwise.

They have also pointed out that species facing competition might evolve mechanisms that promote co¬existence, rather than exclusion.

(iv) Write contribution of Mac Arthur.
Answer:
Mac Arthur had shown that five closely related species of warblers living on the same tree were able to avoid competition and co-exist to behavioural differences in their foraging activities.

Question 24.
Illustrate symbiosis with any four examples.
Answer:
Symbiosis: It is the relationship between two individuals where both partners are benefited.

That following are examples of symbiosis:

1. The Rhizobium bacteria present in the root nodules of leguminous plant roots are an example of symbiosis. Bacteria live in the roots in the form of nodules and avail carbohydrate and other food substances. In exchange, bacteria fix the nitrogen present in the atmosphere and make it useful for plants.
2. Trichonympha, a protozoan parasite, lives inside the intestine of termites. The presence of this protozoan helps the termites to digest the cellulose food and the parasite gets food and shelter.
3. Lichen plants. Lichen is the result of a symbiotic relationship between algae and fungi. In this, algae depend on fungi for water, minerals, salts and safety, whereas fungi get food material prepared by algae.
4. The human intestine contains a large number of symbiotic bacteria that help in the synthesis of vitamin B-complex. Bacteria get necessary nutritional substances from the human intestine and a safe place for living.

Question 25.
Define phenotypic adaptation. Give one example.
Answer:
Phenotypic adaptation involves non-genetic changes in individuals such as physiological modifications, acclimatisation or behavioural changes. Some organisms possess adaptations that are phenotypic, which allow them to respond quickly to a stressful situation.

Example. If a person had ever been to any high altitude place (Rohtang pass near Manali or Mansrover in Tibet), he or she must have altitude sickness because the body does not get enough oxygen at such a height and protect itself from atmospheric hypoxia. But after some time, the body acclimatises itself to the situation by increasing the number of RBC and decreasing the binding affinity of Hb and oxygen.

Question 26.
Name important defence mechanisms in plants against herbivores.
Answer:
Defence mechanisms of plants against herbivorous animals:

1. Formation of thick cuticle on their leaf surface.
2. Formation of leaf spines, e.g. leaf spines in opuntia
3. Modification of leaves into thorns, e.g. Bougainvillea and Duranta
4. Development of spiny margins on leaves.
5. Development of sharp silicated edges in leaves.
6. Many plants produce and store toxic chemicals which cause discomforts to herbivores, e.g. cardiac glucoside by Calotropis, nicotine by tobacco.

Question 27.
Distinguish between the following:
(i) Hibernation and aestivation
Answer:
Differences between hibernation and aestivation:

(ii) Ectotherms and endotherms.
Answer:
Differences between ectotherms and endotherms:

Question 28.
Write short notes on:
(i) adaptations of desert plants and animals. (CBSE2011)
Answer:
Adaptations of desert plants and animals:
(a) Adaptations of desert animals.

• Animals faced with water scarcity as found in arid or desert areas, show two types of adaptations, reducing water loss and the ability to tolerate arid conditions. Kangaroo/Desert rat seldom drinks water. It has a thick coat to minimise evaporative desiccation. The animal seldom comes out of its comparatively humid and cool burrow during the daytime. 90% of its water requirement is met from metabolic water (water produced by respiratory breakdown) while 10% is obtained from food.
• Loss of water is minimised by producing nearly solid urine and faeces.
• Spiny skin and highly cornified in Phrynosoma (horned toad) and Moloch horridus.
• Camels have long legs to stay away from the hot desert surface.

(b) Adaptations of desert plants.

• Plants have thick cuticle, succulent organs where water and mucilage are stored.
• Stomata are sunken to prevent water loss.
• They have a well-developed branched root system.
• They possess a waxy coating on the surface.
• Crassulacean pathway of photosynthesis.

(ii) behavioural adaptations in animals. (CBSE 2011)
Answer:
Adaptations of plants to water scarcities. They are called xerophytes. The above-mentioned adaptation of plants are applicable (see part (a)).

(iii) Behavioural adaptations in animals,
(a) Hibernation
(b) Aestivation
(c) Periodic activity
(d) Camouflage
(e) Migration.

(iv) importance of light to plants.
Answer:
Importance of light to plants.
(a) Source of energy for photosynthesis
(b) Photoperiodism
(c) Pigmentation
(d) Daily rhythm
(e) Plant movements and (f) Growth.

(v) effect of temperature or water scarcity and the adaptation of animals.
Answer:
Effect of temperature or water scarcity and adaptation of animals. Optimum temperature is necessary for animals, survival as all the metabolic activities are driven by enzymes. And enzymes work actively only in a certain optimum range of temperature. Regulators can regulate their body temperature in case of temperature fluctuations in the external environment. Conformers also try to maintain temperature by certain methods but not internally.

Similarly, water is also necessary for the metabolic activities of animals. Various adaptations seen in animals to deal with temperature fluctuations are

• thick fur,
• sweating, short limbs and ears.

Various adaptation to counter the scarcity of water is the ability to use metabolic water, store water, reduced water loss, etc.

Question 29.
With the help of a suitable diagram describe the logistic population growth curve. (CBSE Delhi 2019 C)
Answer:
Logistic popuLation growth curve.

S-shaped Population growth curve (Verhulst-Pearl logistic growth curve)

Unlimited resources result in exponential growth. Many countries have realised this fact and introduced various restraints to limit human population growth. In nature, a given habitat has enough resources to support a maximum possible number, beyond which no further growth is possible. This limit is called carrying capacity (K) for that species in that habitat.

A population growing in a habitat with limited resources shows initially a lag phase, followed by phases of increase and decrease and finally the population density reaches the carrying capacity. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth as explained by the following equation:

where N = Population density at a time t; r = Intrinsic rate of natural increase and K = Carrying capacity,

\(\left[\frac{k-N}{k}\right]\) = Environmental resistance.

Since resources for growth for most animal populations become limiting sooner or later, the logistic growth model is considered a more realistic one.

Question 30.
List any three important characteristics of a population and explain. (CBSE Delhi 2019)
Answer:
Three important characteristics of a population are:

1. Population size and population density
2. Birth or natality rate
3. Death or mortality rate.

• Population size: It is the actual number of individuals in the population. The size of the population keeps changing with time depending on the factors like:
  (a) Food availability
  (b) Weather
  (c) Predation pressure and
  (d) Competition.

Population density is a measure of population size per unit area. The population density in a given habitat during a given period changes due to four basic processes, namely

1. Natality,
2. Mortality,
3. Immigration and
4. Emigration.

While natality and immigration contribute to an increase in the size and density of a population, mortality and emigration contribute to a decrease in them.

So the equation for population growth is: Nt + 1 = Nt + [(B + I) – (D + E)],
where Nt = population density at time t.
B = No of birth I = No of Immigration D = No of death E = No of emigration

• If B + I is more than D – E, the population density increases.
• If B + I is less than D – E, the population density decreases.

Birth or Natality rate. It is generally expressed as the number of births per 1,000 individuals of a population per year. It increases the population size (total number of individuals of a population) and population density. Natal or Birth Rate =

Death or Mortality rate. It is the opposite of the natality rate. It is commonly expressed as the number of deaths per 1,000 individuals of a population per year.

Question 31.
Define mutualism. Give examples.
Answer:
Mutualism: It is a symbiotic relationship between the members of two species in which the two partners are mutually benefited. There is a complete dependence of the partners on each other, and one cannot survive in the absence of the other.

Sometimes the term symbiosis is used as a synonym with mutualism.
Examples:
(a) Mutualism between animal and bacteria. Symbiotic bacteria like Ruminococcus are found in the rumen part of the compound stomach of cud-chewing mammals like cattle, sheep, goat, camel, etc. and secrete cellulase enzyme to digest the cellulose of plant food eaten by the ruminants which provide food and shelter to the bacteria.

(b) Mutualism between crab and sea anemone. In this case, a sea anemone gets attached to the back of the hermit crab.

(c) The Mediterranean orchid, Ophrys, employs sexual deceit to get its flowers pollinated. In this orchid, one petal of the flower resembles the female of a bee species in size, colour, markings, etc. The male bee perceives it as a female and pseudo copulate with it. During the process, the pollen grains get dusted on its body.

Question 32.
It is observed that plant-animal interactions often involve co-evolution. Explain with the help of a suitable example. (CBSE Delhi 2019 C)
Or
Mention four significant services that a healthy forest ecosystem provides. (CBSE Delhi 2019)
Answer:
Plants and animals interact for mutual ben¬efit. Plant-animal interactions often involve co-evolution of mutualism, that is, the evolution of flower and its pollinator species are tightly linked with one another. In many species of fig trees, there is a tight one to one relationship with the pollinator species of wasp. It means that a given fig species can be pollinated only by its partner wasp species and no other species.

The female wasp uses the fruit not only at the oviposition site but also uses the developing seeds within the fruit for nourishing its larvae. The wasp pol¬linates the fig inflorescence while searching for suitable egg-laying sites. In return for the favour of pollination, the fig offers the wasp some of its developing seeds as food for the developing wasp larvae.

Question 33.
(i) Compare, giving reasons, the J-shaped and S-shaped models of population growth of a species.
Answer:
There are two models of population growth-exponential growth and logistic growth.
(a) Exponential growth: This growth occurs where the resources, i.e. food and space, are unlimited. The equation can be represented as follows:
\(\frac{\mathrm{dN}}{\mathrm{dt}}\) = (b-d) x N

Let (b-d) = r
\(\frac{\mathrm{dN}}{\mathrm{dt}}\) = rN or N_t=N_oe^rt

N = population size
N_t = population density after time t.
N_o = population density at time zero
r = growth rate
e = base of natural log (2.71828)
b = birth rate
d = death rate
In this growth, when N in relation to time is plotted on a graph, the curve becomes J-shaped.

(b) Logistics growth model: This is a realistic approach as the resources become limited at a certain point in time.

(a) J-shaped curve exponential growth
(b) S-shaped curve logistics growth Every ecosystem has limited resources to support a particular maximum carrying capacity (K). When N is plotted in relation to time t, a sigmoid S-shaped curve is obtained. It is also called Verhulst-Pearl logistic growth.

The equation is:
\(\frac{\mathrm{dN}}{\mathrm{dt}}\)=rN\(\left(\frac{K-N}{K}\right)\)

N = population density at time t
r = growth rate
K = carrying capacity.

(ii) Explain “fitness of a species” as mentioned by Darwin. (CBSE 2017)
Answer:
According to Darwin “Fitness of a species” means reproductive fitness. All organisms after reaching reproductive age have a varying degree of reproductive potential. Some organisms produce more offspring, whereas some organisms produce few offspring only. This phenomenon is also called differential reproduction. The species which produces more offspring are selected by nature.

Question 34.
(i) The following are the responses of different animals to various abiotic factors. Describe each one with the help of an example.
(a) Regulate
Answer:
Regulate: Some organisms are able to maintain homoeostasis by regulating their body temperatures. The mechanisms used by most mammals to regulate their body temperature are similar to what we humans use.

For example, our body temperature remains constant at 37°C. In summer, when the outside temperature is more than our body temperature, we sweat profusely to cool down and when the temperature is much lower than 37° C, we shiver to generate heat. Thus body temperature remains constant.

(b) Conform
Answer:
Confirm: Most of the animals cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. These are called conformers. Heat loss or heat gain is a function of surface area. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside, for example, shrews and hummingbirds.

(c) Migrate
Answer:
Migrate: Organism can move away temporarily from the stressful habitat to a more hospitable area and then return when the stressful period is over.

For example, every winter, the famous Keoladeo National Park in Bharatpur hosts thousands of migratory birds coming from Siberia and other northern regions,

(d) Suspend
Answer:
Suspend: Bacteria, fungi and some lower plants survive unfavourable conditions by forming thick-walled spores. In higher plants, seeds and some other vegetative reproductive structures serve as means to tide over periods of stress. They do so by reducing their metabolic activity and going into a state of dormancy.

(ii) If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of the population of butterflies during that period. (CBSE 2018)
Answer:
Death Rate = \(\frac{8}{80}\) = 0.1 per week

Question 35.
(a) Identify the features of a stable biological community.
Answer:
(a) Features of the stable biological community.

• It is stable.
• A stable biological community is not replaced by any other community.
• The environment becomes moister and shadier.
• Communities should have greater biodiversity for greater stability.
• It should be able to prevent invasion by alien species.
• It should be able to restore itself in a short period of time.

(b) How did David Tilman’s findings link the stability of a biological community to its species richness? (CBSE Delhi 2019 C)
Answer:
David Tilman’s with his experiments established that the stability of a community depends on its species richness.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 12 Biotechnology and its Applications. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 12 Important Extra Questions Biotechnology and its Applications

Biotechnology and its Applications Important Extra Questions Very Short Answer Type

Question 1.
What is a transgenic organism?
Answer:
An organism that carries a foreign functional gene in its genome is termed a transgenic organism.

Question 2.
Write two applications of biotechnology.
Answer:

1. Treatment of diseases.
2. Preparation of processed fortified food.

Question 3.
What are probes?
Answer:
It is a single-stranded DNA or RNA, tagged with a radioactive molecule, which is complementary to the DNA in a clone of cells. It is used for detecting the presence of nucleotides complementary to the probe.

Question 4.
Name two diseases that can be treated by producing biological compounds in transgenic animals.
Answer:
Cystic fibrosis, rheumatoid arthritis, Alzheimer’s disease, cancer, and emphysema.

Question 5.
Name the toxin produced by Bacillus Thurinsiensis.
Answer:
Bt Toxin.

Question 6.
What is the utility of the Bt-toxin gene?
Answer:
Bt-Toxin gene provides Bt-toxin which is involved in providing resistance to cotton plants against insects.

Question 7.
Bt-toxin protein exists in which form?
Answer:
Inactive protoxins.

Question 8.
How is inactive Bt-toxin converted into active form? (CBSE Outside Delhi 2019)
Answer:
The inactive toxin is converted into active form due to the alkaline pH of the gut of insects which solubilizes the crystal converting the toxin to its active form.

Question 9.
How does Bt toxin cause the death of insects?
Answer:
Activated Bt toxin binds to the surface of midgut epithelial cells and creates pores in it that cause cell swelling and lysis. It finally leads to the death of the insect.

Question 10.
Name a few forms of cry gene.
Answer:
cry I Ac, cry II Ab, cry III Ab, and cry III Bb.

Question 11.
List the specific insects killed by:
(i) cry I Ac and
(ii) cry II Ab.
Answer:
cry I Ac, cry II Ab-both control cotton bollworm.

Question 12.
Name the insects killed by proteins coded by cry III Ab and cry III Bb.
Answer:

1. Colorado potato beetle
2. corn rootworm.

Question 13.
What is unique about transgenic animals?
Answer:
Animals that have their DNA manipulated to possess and express a foreign gene are known as transgenic animals. e.g. Rabit, sheep, cows, fish, etc.

Question 14.
How infestation of Meloidogyne incognita was prevented in the Tobacco plant?
Answer:
An infestation of Meloidogyne incognita was prevented on the basis of RNA interference. This method involves the silencing mRNA by complementary dsRNA molecule that binds to mRNA and prevents its translation.

Question 15.
What is the silencing of mRNA?
Answer:
The binding of single-stranded mRNA with complementary and double-stranded RNA to prevent translation of mRNA is called silencing of mRNA.

Question 16.
What is the source of the complementary strand in mRNA silencing?
Answer:

• Viruses having RNA genomes.
• Mobiles genetic elements (transposons).

Question 17.
How is dsRNA prepared?
Answer:
Reverse transcription.

Question 18.
Name the genetically engineered insulin.
Answer:
Humulin.

Question 19.
Write the name of the transgenic protein used to treat emphysema.
Answer:
Alpha-1-antitrypsin.

Question 20.
How is Indian basmati unique?
Answer:
It is unique for its aroma and flavor.

Question 21.
What is complementary DNA (cDNA)?
Answer:
DNA synthesized on RNA template with the help of reverse transcriptase.

Question 22.
Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin. (CBSE 2018)
Answer:
The proinsulin is cleaved to remove extra stretch called the C-peptide to form mature insulin having only A-chain and B-chain joined by a disulfide bond.

Question 23.
What is the application of genetically engineered bacterium namely Pseudomonas Putidal?
Answer:
Pseudomonas putida is used for scavenging oil spills by digesting hydrocarbons of crude oil.

Question 24.
How did the first transgenic cows Rosie differ from other cows with respect to the quality of milk? (CBSE 2008)
Answer:
Rosie produced a human protein (alpha-lactalbumin) enriched milk which is nutritionally a more balanced product for human babies.

Question 25.
State the role of C-peptide in human insulin. (CBSE 2014)
Answer:
C-peptide maintains its nature as pro-hormone (pro-insulin) and during maturation, it is removed. Thus proinsulin matures into insulin.

Biotechnology and its Applications Important Extra Questions Short Answer Type

Question 1.
List three critical research areas of biotechnology.
Answer:
Three critical research areas of biotechnology are:

1. Providing the best catalyst in the form of an improved organism usually a microbe or pure enzyme.
2. Creating optimal conditions through engineering for a catalyst to act, and
3. Downstream processing technologies to purify the protein/organic compound.

Question 2.
Give the few characteristics of GMOs. (CBSE Delhi 2019)
Answer:
Genetically modified organisms:

1. They are capable of producing pharmaceutically useful proteins.
2. They are capable of producing en¬hanced, modified, or new metabolites.
3. They can be used for crop protection by control of insects, fungal diseases, frost damage, etc.
4. They degrade non-biological wastes and detoxify toxic wastes.
5. They show enhanced nitrogen fixation.

Question 3.
List a few transgenic organisms and their potential application. (CBSE Delhi 2019)
Answer:
Transgenics and their potential applications:

Question 4.
In view of the current food crisis, it is said that we need another green revolution. Highlight the major limitations of the earlier green revolution.
Answer:

1. Excessive use of fertilizers and pesticides which are polluting the water bodies, soil, and food items.
2. It was related to better management practices that can improve food availability to a limited extent.
3. Genetic cap for improvement in food yield.

Question 5.
Differentiate between diagnostics and therapeutics. Give one example for each category.
Answer:
Difference between diagnostics and therapeutics:

Question 6.
Gene therapy can cure important genetic disorders in humans. Comment.
Answer:
Through the “human genome project,” most human genes and sequences have been identified, genetic disorders such as Eczema, cancer, hemophilia, thalassemia, and cystic fibrosis can be cured by the insertion of correct genes into these patients.

Question 7.
What are the advantages of molecular diagnostic over conventional methods?
Answer:
Advantages of molecular diagnostics:

1. Early diagnosis is not possible using conventional methods, but by using rDNA technology and PCR, early diagnosis is possible.
2. It is also a powerful technique to identify many genetic disorders.
3. It is used to detect mutations in suspected cancer patients.

Question 8.
List two uses of cloned genes in molecular diagnostics.
Answer:

1. Cloned genes, when expressed to pro¬duce recombinant proteins, help in developing sensitive diagnostic techniques.
2. Cloned genes are used as probes to detect the presence of its complementary DNA strand; mutated genes will not hybridize with the probe and hence do not appear on the photographic film.

Question 9.
How is early detection of infectious diseases possible by molecular diagnostics?
Answer:
Molecular diagnostic of early detection of infectious diseases:

1. A low concentration of viral or bacterial DNA in a host body can be detected (much before the symptoms of the disease appear) by polymerase chain reaction (amplification).
2. Clones of genes can be used as probes to detect the presence of complementary (normal) strands of DNA in a mutant-clone. Hybridization does not occur and hence the radioactivity does not appear in the (autoradiography) photographic films.

Question 10.
How was insulin obtained before the advent of rDNA technology? What were the problems encountered?
Answer:
Before the advent of rDNA technology, insulin was obtained from slaughtered cattle and pigs.
Problems:

1. Insulin obtained from slaughtered cattle and pigs was slightly different from human insulin. It had a harmful effects over long periods.
2. The drug has been eliciting an immune response in some patients.

Question 11.
Why has the Indian Parliament cleared the second amendment of the country’s patents bill?
Answer:
The major change in the patent regime achieved through the second amendment is not in the area of medicine and drugs but in the area of seeds and plants, especially genetically engineered seeds. It has opened the flood gates for patenting genetically engineered seeds.

Question 12.
Give any two reasons why the patent on Basmati should not have gone to an American Company.
Answer:

1. In India, Basmati rice is being cultivated for several years.
2. American company by producing hybrids of this scented (basmati) rice cannot claim to have the patent rights.

Question 13.
What is a gene library?
Answer:
Gene Library: Several clones of cells each containing one of a few foreign genes are finally obtained, representing almost all the genes of an organism, it is termed the gene library of that organism. From that gene library, it is possible to identify a clone containing the gene of interest.

In order to obtain the gene library of an organism, its genome is first to cut into smaller DNA fragments containing one or a few genes, and such fragments can be cloned in the cell where such a cell multiplies to form a group of cells, all cells have same foreign DNA and are termed clone.

Question 14.
What is a reporter or marker gene?
Answer:
A reporter or marker gene produces a phenotype that is either easily and specifically detected or which allows a differential multiplication of the cells.

Question 15.
Why is the use of probes considered better than conventional diagnostic tools for disease diagnosis?
Answer:
Probes are better than conventional diagnostic tools because:

1. They are highly specific, relatively rapid, and much simpler.
2. They are extremely powerful especially when combined with PCR, even a single molecule in the test sample can be detected.
3. Since the culture of microbe is not required, the risk of accidental infection to laboratory personnel is eliminated.

Question 16.
Name different transfection methods.
Answer:
Calcium phosphate precipitation, direct microinjection, retrovirus infection, lipofection, particle gun delivery, and electroporation.

Question 17.
Why mice are considered the most suitable animals for transgenic production?
Answer:
The mouse is preferred for studies of gene transfers due to its many favorable features like a short estrous cycle and gestation period, production of several offspring per pregnancy, convenient in vitro fertilization, production, and maintenance of embryonic stem cell lines.

Question 18.
Define ‘Germline gene therapy.
Answer:
It is a therapy in which germ cells, i.e. sperms or eggs (even zygotes) are modified by the introduction of functional genes which are ordinarily integrated into their genomes. Therefore, the change due to therapy is heritable and passed on to later generations.

Question 19.
Write the advantages of recombinant therapeutics. How many of them have been approved the world over for human use and how many are available in the Indian market?
Answer:
Advantages of Recombinant Therapeutics:

1. The recombinant therapeutics do not induce unwanted immunological responses like similar products of non-human origin.
2. About 30 recombinant therapeutics have been approved the world over.
3. 12 of them are being marketed in India.

Question 20.
What is interest-sensitive speciesism? Is it one of the ethical issues related to transgenic animals?
Answer:
The use of animals in biotechnological research causes greater suffering to the animals. But most people seem to accept some animal suffering to serve the basic interest and welfare of mankind; this attitude has been termed as interest-sensitive speciesism. It is one of the most common ethical issues.

Question 21.
Name a few useful products obtained from animal cell lines.
Answer:
Useful products obtained from animal cell lines:

1. Production of vaccines for influenza, measles, and mumps from chick embryo fluid.
2. Production of vaccines for rabies and rubella from duck embryo fluid.

Question 22.
Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of DNA technology and the chemistry of oil?
Answer:
The genes for the formation of oil in the seed should be identified. The specific gene can be removed by using enzyme restriction endonucleases. Such DNA molecules should be treated with DNA ligases to seal at the broken ends. These cells when grown in a minimum nutrient medium, under aseptic conditions will differentiate into a new plant whose seeds will not have oil in them.

Question 23.
Find out from the Internet what is Golden Rice.
Answer:
Golden Rice. It is genetically engineered rice rich in Vitamin A. It was prepared by introducing three genes involved in the biosynthetic pathway for carotenoid, the precursor of vitamin A. The color of golden rice is yellow due to the synthesis of provitamin A in the entire grain.

Question 24.
Describe the responsibility of GEAC, set up by the Indian Government. (CBSE 2009)
Answer:

1. Genetic Engineering Approval Committee (GEAC) makes decisions regarding the validity of GM research.
2. It also ensures the safety of introducing GM organisms for public services.

Question 25.
Why insulin is being extracted from bacteria rather than animal sources?
Or
Name the source from which insulin was extracted earlier. (CBSE 2011)
Answer:
Insulin for the use of diabetic patients was earlier extracted from the pancreas of slaughtered cows and pigs. It caused allergy and other reactions in patients, due to foreign proteins. So these days insulin is being extracted from bacteria.

Question 26.
What are embryonic stem cells? What stages of early embryonic development are important for generating embryonic stem cells?
Answer:
Embryonic stem cells, as their name suggests, are derived from embryos. Most embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro-in an in vitro fertilization clinic and then donated for research purposes with the informed consent of the donors. They are not derived from eggs fertilized in a woman’s body. Embryonic stem cells are obtained from the inner cell mass of the blastocyst stage of the embryo.

Question 27.
Name the first transgenic cow developed and state the improvement in the quality of the product produced by it. (CBSE Sample Paper 2018)
Answer:

• Name of the first transgenic cow developed: Rosie
• Advantage: It produced human protein-enriched milk (2.4 grams per liter).

Question 28.
What are cry genes? In which organism are they present? (CBSE 2017)
Answer:
Cry genes code for a toxin that is poisonous to some insects thus making plant insect resistant. They are present in the bacterium Bacillus Thuriengiensis.

Question 29.
Name one toxin gene isolated from B. Thuringiensis and its target pest. (CBSE Delhi 2019 C)
Answer:
Cry I AC is a toxin isolated from B. Thuringiensis and its target pest is cotton bollworm.

Question 30.
Why does the toxin produced by B. Thuringiensis not kill the Bacillus? (CBSE Delhi 2019 C)
Answer:
The toxin produced is in inactive form as protoxin. It does not kill the bacteria and attacks only its target pest because protoxin is activated in the optimum pH medium of the gut of insect pest.

Biotechnology and its Applications Important Extra Questions Long Answer Type

Question 1.
Expand GMO. How is it different from a hybrid?
Answer:

• GMO – Genetically modified organism.
• Differences between GMO and Hybrid.

Question 2.
Mention any six fields of application of biotechnology for human welfare.
Answer:
Applications of Biotechnology:

1. Therapeutics
2. Genetically modified crops
3. Molecular diagnostics
4. Processed food items
5. Bioremediation
6. Biological waste treatment
7. Energy production.

Question 3.
“Specific Bt Toxin gene is incorporated into the cotton plant so as to control the infestation of Bollworm”. Mention the organism from which the gene was isolated and explain its mode of action. (CBSE Sample paper 2019-20)
Answer:

• Specific Bt toxin genes isolated from Bacillus Thuringiensis are incorporated into cotton. Cry I AC and Cry II AC control the bollworm.
• Bt gene forms protein crystals that contain a toxin insecticidal protein.
• It is in an inactive state.
• The inactive toxin is converted into active form due to the alkaline pH of the gut which solubilizes the crystal.
• Activated Bt-toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis. It finally leads to the death of the insect.

Question 4.
How is the ELISA test carried out?
Answer:
ELISA (Enzyme-Linked Immunosorbent Assay Test):

1. It is a technique of detecting a very small amount of protein (antibody or antigen) with the help of enzyme peroxidase or alkaline phosphatase and stain-producing substrates like 5-aminosalicylic acid or orthophenylene diamine.
2. The serum is sorbed to the surface of the ELISA plate.
3. An antibody is specific to the antigen for diagnosis placed over an immobilized antigen.
4. The spot is washed to remove the free antibody.
5. Antibody bound to the enzyme is poured over the spot so as to react with com¬plex antibody.
6. The area is washed again to remove the free antibody-enzyme complex.
7. Chromagen is added. It will produce a stain showing the antigen was present.
8. ELISA is a quick method of diagnosis of pregnancy (by detection hCG in urine), AIDS, hepatitis, STDs, thyroid disorder, and Rubella virus.

Question 5.
While creating genetically modified organisms, genetic barriers are not respected. How this can be dangerous in the long run?
Answer:

1. Genetic pollution. The ecological imbalance may occur due to transferring of transgenes from one organism to another.
2. Formation of Superweeds. Due to the introduction of weedicide genes in crops, there is a danger that any such crop may itself become superweed.
3. Formation of super insecticides.
4. Foreign proteins formed with foreign genes may get attacked by the defense system of the organism leading to the formation of defective biochemicals,
5. Transgenes may exhibit changes in their expressivity after attaining certain age and change in environment.

Question 6.
Explain the structure of Insulin. How insulin is synthesized in humans (or mammals)? (CBSE Outside Delhi 2011) Answer:
(i) Insulin is made up of two short polypeptide chains; A and chain B which are linked together by disulfide bridges.

(A), (B) Conversion of proinsulin after removal of C-peptide.

(ii) Insulin is synthesized as pro-hormone (i.e. which is to be processed before becoming functional) which contains an extra stretch called C-peptide which is usually removed during the maturation of insulin.

Question 7.
Explain the social, economical, and environmental implications of genetic engineering techniques.
Answer:

1. Genetically prepared human insulin and edible vaccines will be readily available and also will be economical.
2. Transgenic crop plants for human consumption may cause concern for safety due to unwanted properties they may have.
3. Some people believe that transgenic plants and animals can solve many human problems especially hunger and disease.

Question 8.
Write a short note on:
(i) Production of human growth hormone by E. coli.
Answer:
Production of human growth hormone by E. coli. The Human growth hormone is produced commercially by transgenic Escherichia coli. The pituitary gland of humans produces growth hormones that regulate growth and development. However, in children stunted growth occurs due to deficiency of the hormone called pituitary dwarfism. For this, the hGH is now available as a recombinant protein.

The high-coding DNA sequence is linked with the bacterial signal sequence of E. coli. The hGH is secreted into the periplasmic space of bacterial cells by the signal peptides wherefrom the protein is purified.

(ii) Animals as organ donors for humans.
Answer:
Animals as organ donors for humans. Organ transplantation from animals to humans is called xenotransplantation. The first experiment was done in 1906 by French Surgeon Mathieu Jaboulay who implanted a pig’s kidney into one woman and a goat’s liver into another woman, but it was not successful.

Though now, organ transplantation from animals has been made possible in America and the United Kingdom. Of all, baboons and pigs have favored xenotransplant donors. Pig organs have been transplanted to humans several times in the last few years. Baboons are genetically close to humans, so they are most often used. Six baboon kidneys were transplanted into humans in 1964. Today, however, xenotransplantation is still experimental and there is a serious risk to the procedures.

(iii) Plant Variety Protection and Farmers’ Right Act.
Answer:
Plant Variety Protection and Farmers’ Right Act. This act provides the establishment of an effective system for the protection of plant breeder’s rights. It gives concurrent attention to the right of farmers, breeders and researchers, and the protection of public interest. Public interest is related to issues like compulsory licensing of rights and to the import of varieties incorporating Genetic Use Restriction Technology.

Question 9.
Explain the following terms in one or two sentences: intellectual property rights, humulin, and biofortified foods.
Answer:
1. Intellectual Property Rights: It is the general term covering patents, copyright, trademark, industrial designs, geographical indications, protection of layout designs of integrated circuits, and protection of undisclosed information (trade secrets).

2. Humulin: It is a crystalline suspension of human insulin. It is made using a chemical process called recombinant DNA technology and is of various types (Humulin R, U, N, L, 70/30, 50/50) depending on the percentage of insulin present in suspension. Humulin does not come from human beings, but they are synthesized in special non¬disease producing special lab strains of E. coli which are genetically altered by the addition of the gene for human insulin production. Humulin is identical in chemical structure to human insulin and is made in a factory by recombinant DNA technology.

3. Biofortified foods: They are the modified food rich in nutritional values. Biofortification is the process of breeding food crops that are rich in bioavailable micronutrients. These crops fortify themselves, they toad high levels of minerals and vitamins in their seeds and roots, which are harvested and eaten.

Question 10.
What are transgenic bacteria? Illustrate using any one example.
Answer:
Those bacteria whose DNA is manipulated to possess and express an extra (foreign) gene are known as transgenic bacteria.
Example: Human Growth hormone production by transgenic Escherichia coli.

1. The pituitary gland of humans produces growth hormones that regulate growth and development.
2. However, in children stunted growth occurs due to deficiency of the hormone which is called pituitary dwarfism.
3. For this, the hGH is now available as a recombinant protein.
4. The hGH-coding DNA sequence is linked with the bacterial signal sequence of E. coli.
5. The hGH is secreted into the periplasmic space of bacterial cells by the signal peptides wherefrom the protein is purified.

Question 11.
Write properties of stem cells. How is the population of stem cells maintained?
Answer:
Properties of stem cells:
The classical definition of a stem cell requires that it possess two properties:

1. Self-renewal: The ability to go through numerous cycles of cell division while maintaining the undifferentiated state,
2. Potency: The capacity to differentiate into specialized cell types. In the strictest sense, this requires stem cells to be either totipotent or pluripotent- to be able to give rise to any mature cell type, although multipotent or unipotent progenitor cells are sometimes referred to as stem cells. Apart from this, it is said that stem cell function is regulated in a feedback mechanism.

1. Self-renewal:
Two mechanisms exist to ensure that a stem cell population is maintained:

• Obligatory asymmetric replication: A stem cell divides into one mother cell that is identical to the original stem cell, and another daughter cell that is differentiated.
• Stochastic differentiation: When
  one stem cell develops into two differentiated daughter cells, another stem cell undergoes mitosis and produces two stem cells identical to the original.

2. Totipotency
They have the potential to develop into any cell found in the human body.

Question 12.
Show with a simple sketch the location of stem cells and their role in treatment.
Answer:
Stem cells:

Diseases and conditions where stem cell treatment is being investigated.

Question 13.
(i) Why are transgenic animals so called?
Answer:
Animals that have had their DNA manipulated to possess and express (foreign) genes are called transgenic animals.
Example: Transgenic mice, transgenic rabbits.

(ii) Explain the role of transgenic animals in (a) vaccine safety (b) biological products with the help of an example for each.
Answer:
(a) Role of transgenic animals in vaccine safety:

• Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans.
• Transgenic mice are being used to test the safety of the polio vaccine.

(b) Role of transgenic animals in biological products: In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk of 2.4 gm per liter. The milk contained the human alpha-lactalbumin and was a more balanced product for human babies.

Question 14.
Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain. (CBSE 2012)
Answer:

1. Genes for making Bt cotton resistant to bollworm attack:
   1. acrylic
   2. cry IIAb
2. Specific Bt toxin genes are isolated from Bacillus Thurinsiensis and incorporated into the cotton plant.
3. The toxin is coded by a gene name cry.
4. The protein synthesized by these is insecticidal protein. It is present as an inactive protoxin.
5. Once the insect ingests the protoxin it is converted into the active form of toxin due to the alkaline medium of the gut.
6. The activated toxin binds to the surface of midgut epithelial cells and creates pores in them.
7. It causes swelling and breakdown and eventually leads to the death of the insect.

Question 15.
Explain the various steps involved in the production of artificial insulin. (CBSE 2017)
Or
Explain how Eli Lilly, an American company, produced insulin by recombinant DNA technology. (CBSE Delhi 2018C)
Answer:
Genetically engineered insulin:

1. Insulin contains two short polypeptide chains: chain A and chain Blinked together by disulfide bridges.
2. In mammals, insulin is synthesized as a pro-hormone. It contains an extra stretch called C-peptide.
3. C-peptide is absent in the mature insulin and is removed during maturation into insulin.
4. Production of insulin by rDNA techniques was achieved by an American company, Eli Lilly in 1983. It prepared two DNA sequences corresponding to A and B, chains of human insulin, and introduced them in plasmids of E. coli for production.
5. The Aand B chains produced were separated, extracted and combined, by creating disulfide bonds to form human insulin.

Question 16.
(i) What are transgenic animals?
Answer:
Animals whose DNA has been manipulated to possess and express an extra/foreign gene are known as transgenic animals.

(ii) Name the transgenic animal having the largest number amongst all the existing transgenic animals.
Answer:
Mice

(iii) Mention any three purposes for which these animals are produced. (CBSE Delhi 2018C)
Answer:
(a) Transgenic animals are designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its developments, e.g. information is obtained as to how insulin has a role as a growth factor.
(b) Transgenic animals are designed to increase our understanding of how genes control the development of diseases; they serve as models for human diseases.
(c) Transgenic mice are being developed to test the safety of vaccines, e.g. polio vaccine has been tested on mice.

Question 17.
Explain the following terms in not more than 70 words.
(i) Single-cell proteins (SCP)
Answer:
Cells from different kinds of organisms such as bacteria, filamentous fungi, yeast, and algae are treated in different ways so that they are used as food or feed, are called single-cell protein. The biomass is obtained from both unicellular and multicellular microorganisms. The common substrate used for preparing such food containing SCP ranges from whey sawdust, and paddy straw. SCP provides a valuable protein-rich supplement in the human diet.

(ii) Biopatent
Answer:
A patent is a right granted by a Government to an inventor to prevent others to make commercial use of such an invention. At present patents that are granted for biological entities and the various products obtained from these organisms, are termed as biopatent.

Biopatents are being granted for the following:
(1) Strains of microorganisms
(2) Cell lines
3) Genetically modified strains of living organisms
(4) DNA sequences
(5) The proteins prepared by DNA sequences
(6) Biotechnological process
(7) Production process
(8) Products
(9) Product application.

(iii) Bioethics
Answer:
Bioethics is a set of standards that may be used to regulate our activities in relation to biological works.

The major bioethical concerns are as follows:
(a) Introduction of transgenes from one species to another violates the integrity of species.
(b) Transfer of human genes to other animals and vice versa is against ethics.
(c) Making of the clone.
(d) May cause risk to biodiversity.
(e) Suffering from animals used in biotechnology will increase.

(iv) Biopiracy
Answer:
The exploitation of patent biological resources without proper permission is called biopiracy. The collection of such material without a benefit-sharing agreement is likely to find its way into the list of criminal violations in many countries.

(v) Genetically modified food
Answer:
The food prepared from the production of genetically modified crops is called genetically modified food (GM food). It contains proteins produced by a transgene.

Question 18.
Briefly explain why are Transgenic animals produced? (CBSE Delhi 2013)
Answer:
Transgenic animals:
Transgenic animals are produced for the following purposes:

1. Transgenic animals are designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its developments, e.g. information is obtained as to how insulin has a role as a growth factor.
2. Transgenic animals are designed to increase our understanding of how genes control the development of diseases; they serve as models for human diseases.
3. Transgenic animals that produce useful biological compounds are created by introducing a portion of the DNA that codes for that product, e.g. a-1 antitrypsin is produced for curing emphysema.
4. Transgenic mice are being developed to test the safety of vaccines, e.g. polio vaccine has been tested on mice.
5. Transgenic animals with more sensitivity to toxic substances are being developed to test the toxicity of drugs.

Question 19.
Describe the hazards of transgenic animals.
Answer:
Hazards of transgenic animals:

1. Proteins: Genes introduced in various organisms operate through the synthesis of polypeptide proteins and enzymes. However, foreign proteins are generally attacked by the defense system resulting in damaged biochemicals which may prove harmful and in the long term produce allergy.
2. Human organs: Replaceable human organs like kidneys, liver, heart, pancreas, etc. can be obtained only from autografts and isografts. Will it be ethical to grow the human body, human body organs for obtaining the required organs?
3. Human cloning: This can solve the problem of infertility. However, such a method of human reproduction will destroy the family system, fine human feelings, and the fabric of human society.
4. Recreation: It is not only a fancy but also the desires of numerous children, adults, and elders to see dinosaurs live.

Question 20.
Compare and contrast the advantages and disadvantages of the production of genetically modified crops.
Or
Write advantage of GM crops. (CBSE Outside Delhi 2019)
Answer:
The advantages of the production of genetically modified crops are:

1. They have proved to be extremely valuable tools in studies on plant molecular biology, regulation of gene action, identification of regulatory/ promontory sequences.
2. Genetically modified crops have improved agronomic and other features such as resistance to biotic and abiotic stresses.
3. Over-ripening losses can be reduced, e.g. flavor saves tomato.
4. Nutritional values are improved, e.g. Golden rice has high vitamin A content.
5. Viral resistance can be introduced.
6. The number of pharmaceuticals like insulin, interferon, blood clotting factors are improved.
7. Insect resistance can be introduced, e.g. cry gene can be introduced into cotton, wheat, and rice from Bacillus Thuringiensis.

The main disadvantages of the production of genetically modified crops are:

1. Many transgenes are expressed at low levels which usually limit their usefulness.
2. Sometimes, the expression of transgenes is suppressed in transgenic plants, this is called gene silencing.
3. The undesirable features are also carried along with desirable features in transgenic plants such as necrosis, reduced growth, sterility, etc.
4. Genetic pollution can be there.
5. Weeds also become resistant.
6. Bt cotton, Bt wheat also destroy pollinators and disseminators.
7. The product of transgene may be allergic or toxic.

Question 21.
Why is the introduction of genetically engineering lymphocyte into an ADA deficiency patient, not a permanent cure? Suggest a possible permanent cure. (CBSE 2010, 2011)
Or
Explain how a hereditary disease can be corrected? Give an example of the first successful attempt made towards this objective. (CBSE 2011, 2019 C)
Or
Explain enzyme replacement therapy to treat ADA deficiency. (CBSE Outside Delhi 2016, 2019 C)
Or
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency? (CBSE Delhi 2011, 2013, 2016)
Or
Two children A and B aged 4 and 5 years respectively visited a hospital with a similar genetic disorder. Girl A was provided enzyme-replacement therapy and was advised to revisit periodically for further treatment. Girl B was, however, given therapy that did not require a revisit for further treatment.
(a) Name the ailments the two girls were suffering from.
(b) Why did the treatment provided to girl A require repeated visits?
(c) How was girl B cured permanently? (CBSE Delhi 2019)
Answer:
Gene Therapy. It is defined as the introduction of a normal functional gene into cells that contain the defective allele of the concerned gene with the objective of correcting a genetic disorder or an acquired disorder.

Treatment of ADA deficiency:

1. Gene therapy was used to correct the genetic disorder called Severe Combined Immunodeficiency (SCID) syndrome produced by adenosine deaminase (ADA) deficiency.
2. In this, Normal ADA gene copies were produced by cloning.
3. Packed into a retrovirus, most of the viral genes were replaced by the ADA gene.
4. Lymphocytes were isolated from the patients.
5. Recombinant DNA of the recombinant retroviruses was used to infect the lymphocytes.
6. The infected cells expressing the ADA gene were injected back into the patients.
7. The normal ADA gene was then expressed in the patients and ADA deficiency is partially corrected. If the gene isolated from bone marrow cells producing ADA is introduced into embryonic cells at early stages, it could provide a permanent cure.

Question 22.
How is the transgenic tobacco plant protected against Meloidogyne incognita? Explain the process? (CBSE 2009)
Or
Explain the process of RNA interference. (CBSE Delhi 2011, 2016)
Or
How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in the correct sequence. (CBSE 2018, Sample paper 2020)
Answer:
Protection of tobacco plant against Nematodes, Meloidogyne incognita:

1. A nematode Meloidogyne incognita infects tobacco plants and reduces their yield.
2. The specific genes (in the form of cDNA) from the parasite are introduced into the plant using Agrobacterium as the vector.
3. The genes are introduced in such a way that both sense/coding RNA and antisense RNA (Complementary to the sense/coding RNA) are produced.
4. Since these two RNAs are complementary, they form a double-stranded RNA (ds RNA)
5. This neutralizes the specific RNA of the nematode, by a process called RNA- interference.
6. As a result, the parasite cannot live in the transgenic host, and the transgenic plant is protected from the pest.

Question 23.
What are the ethical concerns of biotechnology?
Answer:

1. Biotechnology is producing newer genotypes. Some of them can be extremely harmful due to intragenomic interactions and mutations.
2. It introduces unfamiliar proteins into transgenics which may react to form toxins and allergens.
3. The genes introduced into crops can pass into weeds through pollen transfer. It will produce superweeds.
4. It is going to cause genetic pollution which is likely to disturb natural balance in a big way.
5. Animals employed in experiments of biotechnology are made to suffer.
6. Animals being used to produce particular structures and pharmaceutical proteins are reduced to the status of factories.
7. As a gene is introduced from outside into an organism, its integrity as a species is violated.
8. Transfer of genes from human beings to specific animals or vice-versa violates the concept of humanness.
9. Biotechnology has no respect for living beings. Its only goal is to exploit them for commercial use in benefitting human society.
10. In their race to gain supremacy over others, companies and individuals are rushing for biopatents even of those products which are produced through the traditional knowledge of tribals, communities, and societies.

Question 24.
The Green Revolution succeeded in increasing the yield of crops but it is not sufficient to feed the growing human population. Thus there is a need for another green revolution.
(i) Name the technique which will help in increasing the yield of crops.
Answer:
Genetic engineering (Recombinant DNA technology).

(ii) Name any two genetically modified crops.
Answer:
(a) Bt cotton
(b) ‘Flavr Savr Tomato’

(iii)What is golden Rice’?
Answer:
Golden rice is a transgenic variety of rice (Oryza sativa) that contains good quantities of (3-carotene (provitamin A – inactive state of vitamin). Since the grains of the rice are yellow in color due to [3-carotene, the rice is called golden rice.

(iv) Name a natural genetic engineer.
Answer:
Agrobacterium tumefaciens.

Question 25.
How have transgenic animals proved to be beneficial in:
(i) Production of biological products
(ii) Chemical safety testing. (CBSE 2014)
Answer:
(i) Production of biological products:
(a) Medicines required for treating human diseases are obtained by genetic engineering.
(b) a-1-antitrypsin used to treat emphysema.
(c) Transgenic cow ‘Rosie’ produces human-protein enriched milk.
(ii) Chemical safety (Toxicity/safety testing) Transgenic animals are made that carry genes that make these more sensitive toxic substances than non-transgenic animals.

Question 26.
List the disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs.
Answer:

1. A slaughtered animal produces very little hormone so that the demand was always higher than the supply.
2. It is unethical to slaughter animals for obtaining the drug.
3. Contamination was quite common.
4. The immune response is common.

Question 27.
List the advantages of recombinant insulin.
Answer:

1. Recombinant insulin is exactly similar to human insulin and is, therefore, also called humulin.
2. It is available in pure form with little chances of contamination.
3. There is no slaughtering of animals.
4. There is no immune response or any other side effect.
5. There is enough manufacturing capacity so that the chances of short supply are few.

Question 28.
Explain the process of synthesis of insulin.
Answer:
Production of human insulin: Gene transfer involves essentially the following stages:

Steps involved in gene transfer for the production of human insulin:

1. Isolation of donor or DNA segment. A useful DNA segment is isolated from the donor organism.
2. Formation of Recombined DNA (rDNA). Both the vector and donor DNA segments are cut in the presence of restriction endonuclease. In the presence of ligase DNA segments of both are joined to form rDNA.
3. Production of Multiple Copies of rDNA. The next step in the process is the production of multiple copies of this recombinant DNA.
4. Introduction of rDNA in the recipient organism. This rDNA is inserted into a recipient organism.
5. Screening of the transformed cells. The recipient (host) cells are screened for the presence of rDNA and the product of the donor gene. The transformed cells are separated and multiplied, using an economical method for its mass production.