CBSE Class 8

In this page, we are providing Reaching the Age of Adolescence Class 8 Extra Questions and Answers Science Chapter 10 pdf download. NCERT Extra Questions for Class 8 Science Chapter 10 Reaching the Age of Adolescence will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 10 Extra Questions and Answers Reaching the Age of Adolescence

Extra Questions for Class 8 Science Chapter 10 Reaching the Age of Adolescence with Answers Solutions

Reaching the Age of Adolescence Class 8 Extra Questions Very Short Answer Type

Question 1.
What is Adam’s apple?
Answer:
The protruding part of the throat in males is called Adam’s apple.

Question 2.
Name the hormone in female that is produced by ovaries and helps in development of mammary glands.
Answer:
Estrogen

Question 3.
Whose height grow faster initially boys or girls?
Answer:
Girls

Question 4.
Name a gland which transports secretions through ducts.
Answer:
Sweat glands/salivary glands/ oil gland (any one).

Question 5.
What is puberty?
Answer:
The age at which boys and girls become capable of reproduction.

Question 6.
What are hormones?
Answer:
The chemical substances produced by endocrine glands are called hormones.

Question 7.
How long is a woman’s reproductive life lasts?
Answer:
Menarche to menopause.

Question 8.
Name the female hormone.
Answer:
Estrogen

Question 9.
Which gland is called master gland?
Answer:
Pituitary gland

Question 10.
What is a balanced diet?
Answer:
The meal that includes all nutrients is called a balanced diet.

Question 11.
What is menstruation?
Answer:
Extrusion of uterus lining and blood along with the unfertilised egg from the vagina is called menstruation.

Question 12.
What is menarche?
Answer:
The first menstrual flow begins at puberty and is termed as menarche.

Question 13.
What is menopause?
Answer:
Stoppage of menstruation is called menopause.

Question 14.
What causes goitre?
Answer:
Deficiency of thyroxine hormone.

Question 15.
Which gland secretes thyroxine?
Answer:
Thyroid gland

Question 16.
What are chromosomes?
Answer:
The thread-like structures in the nucleus are called chromosomes.

Question 17.
How many chromosomes are present in human cell?
Answer:
23 pairs or 46 chromosomes.

Question 18.
How many sex chromosomes are there in human cell?
Answer:
Two, i.e., one pair.

Question 19.
Which hormone is necessary for normal growth of a person?
Answer:
Growth hormone.

Question 20.
Which gland secretes insulin?
Answer:
Pancreas

Question 21.
What causes diabetes?
Answer:
Deficiency of insulin.

Question 22.
Name the chromosome present in a female.
Answer:
X chromosome

Question 23.
Name the chromosome present in a male.
Answer:
X and Y chromosomes

Question 24.
Which chromosome does the unfertilised egg contain?
Answer:
X chromosome

Question 25.
Which hormone balances the proportion of salts in the blood?
Answer:
Adrenaline

Question 26.
What decides the sex of an unborn child?
Answer:
Sex chromosome of father.

Question 27.
Name the glands other than the pituitary gland.
Answer:
Thyroid, pancreas and adrenals.

Question 28.
When does the puberty ends?
Answer:
Puberty ends when an adolescent reaches reproductive maturity.

Question 29.
Do the boys and girls undergo same physical changes at puberty?
Answer:
No

Question 30.
Why do we need to have a balanced diet?
Answer:
To keep the body healthy.

Reaching the Age of Adolescence Class 8 Extra Questions Short Answer Type

Question 1.
What is meant by adolescence?
Answer:
Growing up is a natural process. The period of life, when the body undergoes several changes leading to reproductive maturity, is cabled adolescence. The adolescence period is 11 to 19 years of age.

Question 2.
What is puberty?
Answer:
The period during which adolescent boys and girls attain sexual maturity and become capable of reproduction is called puberty. Puberty age of female is 10 to 12 years while male puberty age is 12 to 14 years.

Question 3.
What is vital change which marks puberty in boys and girls?
Answer:
During puberty, the human body undergoes several changes, but the most important changes which marks puberty is that boys and girls become capable of reproduction.

Question 4.
Why do boys have a hoarse voice at puberty?
Answer:
The voice box or larynx begins to grow at the onset of puberty. This growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple. This leads to voice becoming hoarse.

Question 5.
How does the body shape change at puberty?
Answer:
Body shape changes differently in boys and girls at puberty. Boys have broader shoulders and wider chests. Their muscles grow more prominently than girls. In girls, the region below the waist becomes wider.

Question 6.
Why is adolescence also called teenage?
Answer:
Adolescence period is generally 11 to 19 years of age. Because the period covers the teens, i.e., 13 to 19 years of age, adolescents are also called teenagers.

Question 7.
Why do many young people have acne and pimples during adolescence?
Answer:
During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases. It develops acne and pimples on the face of young boys and girls.

Question 8.
Why are endocrine glands also called ductless glands?
Answer:
Endocrine glands release hormones directly into the blood stream. So, they are termed as ductless glands. For example, pituitary, thyroid, pancreas, etc.

Question 9.
What are secondary sexual characters?
Answer:
At puberty, in girls, breasts begin to develop, the region below the waist become wider, voice become shriller. Boys begin to grow facial hair, i.e., moustache and beard. Boys also develop hair on their chest, the muscles of the body grow more prominently, develop larger voice box which can be seen as a protruding part of the throat called Adam’s apple. In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters.

Question 10.
Explain the development of sex organs in male and female.
Answer:
The male and the female sex organs develop completely at puberty. Male sex organ like testes and penis develop completely. The testes begin to produce the male gametes or sperm. Similarly in girls the ovaries enlarge and egg begins to mature. Ovaries start releasing matured eggs or ovum.

Question 11.
Why do changes occur in human body at puberty?
Answer:
The changes in human body at puberty occur due to release of hormones by different types of glands. Hormones are chemical substances secreted from endocrine glands or endocrine system. Male hormone or testosterone are responsible for changes in male whereas female hormone or estrogen are responsible for changes in female.

Question 12.
What is a pituitary gland?
Answer:
Different types of hormones are secreted by different types of glands. The product of all these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.

Question 13.
How do hormones work in human body?
Answer:
Endocrine glands release hormones into the blood stream to reach a particular body part called target site. The target responds to the hormone. There are many endocrine glands or ductless glands in the body.

Question 14.
What are sex hormones? How do they work in the human body?
Answer:
Sex hormones help boys and girls develop sex organs to enable them for reproduction. These hormones lead them to reproductive maturity.

In girls, estrogen makes the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. Ovaries begin to produce eggs. In boys, testosterone is released by testes. Testes begin to release sperms. Changes in boys is also seen due to this hormone.

Question 15.
What is menstruation?
Answer:
At puberty, in girls the ovaries get enlarged and start producing eggs (ovum). One egg matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg. If the egg is fertilised then it begins to develop and results in pregnancy. If this egg is not fertilised, the released egg and thickened lining of the uterus along with its blood vessels are shed off causing bleeding in female which is called menstruation. It occurs once in about 28 to 30 days.

Question 16.
What are the changes in female at the onset of puberty?
Answer:
There are several changes in females at the onset of puberty. They are:

• growth of hair in armpit and pubic region.
• development of breasts and mammary glands.
• ovaries get enlarged and begin producing eggs.
• menstruation cycle starts; and
• increased activity of sweat and sebaceous glands.

Question 17.
Explain the terms menarche and menopause.
Answer:
The first menstrual flow begins at puberty and is termed as menarche.
At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is called menopause.

Question 18.
What happens when the egg is fertilised?
Answer:
When the egg is fertilised, it begins to divide and then gets embedded in the uterus for further development. Finally the fertilised egg develops into a foetus.

Question 19.
What are the changes in males at puberty?
Answer:
There are various changes in males at puberty.
They are:

• sudden increase in height.
• growth of hair at different parts of body like face, armpit and pubic region, development of moustache and beard.
• development of Adam’s apple in throat, voice becomes hoarse.
• shoulders become broader and chest wider.
• growth of size of reproductive organs like penis, testes begin to produce sperms, etc.

Question 20.
What do you mean by reproductive health?
Answer:
The physical and mental well being of an individual is regarded as an individual’s health. To keep the body healthy, every human being, at any age, needs to have a balanced diet. The person must also observe personal hygiene and undertake adequate physical exercise. Thus, reproductive health refers to the diseases, disorders and conditions that affect the functioning of the male and female reproductive system during all stages of life.

Question 21.
What is the role of hormones in completing the life history of insects and frogs?
Answer:
Hormones play an important role in the completion of life cycle of insects and frogs. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid gland. Thyroxine production requires the presence of iodine in water. Water in which iodine is not, present, the tadpoles cannot become adult.

Question 22.
Which hormone is released by pancreas? What is its function?
Answer:
Insulin is released by pancreatic gland. It regulates sugar metabolism. If insulin is deficient in the body, sugar level becomes high in blood causing diabetes.

Reaching the Age of Adolescence Class 8 Extra Questions Long Answer Type

Question 1.
What changes occur in human at puberty?
Answer:
There are various changes in human at puberty. They are as follows:
(i) Change in height: During puberty, there is sudden increase in height in boys and girls. Initially, girls grow faster in height than in boys. But both reach their maximum height at the age of 18 years.

(ii) Change in voice: Boys develop larger voice box or larynx to form protruding part of throat called Adam’s apple making their voice hoarse, girls have high pitched voice.

(iii) Change in body shape: In boys, shoulders broaden and muscles grow more prominently than in girls. In girls the region below the waist becomes wider.

(iv) Secretion of sweat and sebaceous glands (oil glands) in both boys and girls increases and acne or pimples grow on faces of many youths.

(v) Development of sex organs: In males, testes and penis develop completely. Testes begin producing sperms. In girls, ovaries are enlarged and begin to produce eggs. Both boys and girls reach reproductive maturity.

(vi) In girls, menstruation or periods starts.

(vii) All human beings attain mental, intellectual and emotional maturity at puberty.

(viii) Facial hair like moustache and beard are grown in boys. Hair are grown in armpit and pubic region in both boys
and girls. Breasts are developed in girls. These characters are called secondary sexual characters as they distinguish a male from a female.

Question 2.
Explain the reproductive phase of life in humans.
Answer:
Boys and girls become capable of reproduction at puberty because their testes and ovaries begin to release gametes, i.e., sperms and ova respectively. In girls, reproductive phase of life begins at puberty from 10 to 12 years of age and generally lasts till the age of 45 to 50 years. The ova begin to mature with the onset of puberty. The ovum matures and is released by one of the ovaries once in 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilised and begins to develop. This results in pregnancy.

If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes menstruation. It occurs once in about 28 to 30 days. The first menstrual flow begin at puberty and is termed as menarche. The menstruation stops at the age of 45 to 50. This stage is known as menopause. In male, the reproductive phase begins at puberty at the ages 14-15 and lasts as long as he is healthy.

Question 3.
Mention different types of glands, their functions and hormones secreted by them.
Answer:
There are different types of glands in our body and they secrete different types of hormones which control grotto, behaviour, development and reproduction. The following table shows different types of glands, hormones secreted by them and their functions:

Question 4.
Explain sex determination in human.
Answer:
Sex determination of a baby is done at the time of fertilisation when a male gametes fuse with a female gamete. It depends on male partner whether the baby will be a male child or female child. The chances of child to be male or female actually depend on the chromsomes present in the fertilised eggs or ova. There are 23 pairs of chromosomes in the nuclei of all human beings out of which two are sex chromosomes named X and Y.

A male has one X and one Y chromosome and a female has two X chromosomes. The gametes (egg and sperm) have only one set of chromosomes. The unfetilised egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome.

When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child. Fig. 10.5 shows sex determination in humans.

Question 5.
Explain the term reproductive health. What should we do to maintain reproductive health?
Answer:
The state of physical, mental and social well being of an individual is regarded as an individual’s health. A healthy person is free from disease, tension and anxiety. Reproductive health refers to a state of physical, mental and social well-being in all matters relating to the reproductive system, at all stages of life.

We should take following measures to maintain reproductive health:

• To have a balanced diet: As far as practicable, we should have a balanced diet, i.e., a diet containing proteins, vitamins, carbohydrates, fats and minerals. We can have our food which contain these nutrients.
• To take physical exercise: We should take physical exercise like morning walk, running, etc., daily.
• To maintain personal hygiene: We should maintain personal hygiene to stay fit and healthy. We should wash our body especially pubic region, armpit, etc., properly.
• Avoid harmful drugs: We should avoid taking harmful drugs and alcohol.

Reaching the Age of Adolescence Class 8 Extra Questions HOTS

Question 1.
One day Seema’s uncle visited her place. Seema prepared dinner for him. When she was about to put rock salt on the salad, her uncle interrupted her and asked to put iodised salt instead of rock salt. He also advised her to prefer iodised salt instead of rock salt. Why do you think Seema’s uncle advised her to have iodised salt instead of rock salt?
Answer:
Deficiency of iodine causes goitre disease in our body. This is why Seema’s uncle advised her to have iodised salt.

Question 2.
It is said that height of a child depends upon the genes inherited from the parents. Are there factors other than genes that causes variation in height?
Answer:
Other factors like nutrition, release of growth hormones, exercises, diseases, etc., also have impact on the height of a growing child.

Question 3.
Is a woman responsible for the birth of a girl child? Explain.
Answer:
No, because a woman has eggs of only X chromosomes but a male has sperms of both X and Y chromosomes. It is the type of male chromosome (X or Y) which fuses with the egg and determine the sex of the foetus, i.e., whether it will be male (XY) or female (XX) child.

Question 4.
John and Radha were classmates since childhood. When Radha became eleven years old, she developed a little swelling on her neck. She visited the doctor who started medication for her. After a few years, John also developed a slight protrusion on his throat. He got worried and went to the doctor. But, the doctor assured him that it was a normal feature in boys while they are growing up. Can you think of any reasons for the difference in diagnoses?
Answer:
The swelling on the neck of Radha may be because of insufficient production of thyroxine which results in goitre. However slight protrusion in John’s throat may be due to enlargement of voice box, also known as Adam’s apple, in adolescent boys.

Question 5.
Why we should not take medicines or drugs unless prescribed by a doctor?
Answer:
Certain medicines have specific dosage levels and adverse side effects which if not followed may be proved lethal to us. Drugs can be addictive too and can ruin our health and happiness.

Reaching the Age of Adolescence Class 8 Extra Questions Value Based (VBQs)

Question 1.
Salma had a very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face, her body became taller compared to her face. She got worried of all of the sudden changes. Her mother explained that all these changes are normal and advised her to wash her face at regular intervals.

(a) Why Salma’s mother advised Salma to wash her face at regular intervals?
(b) What is the reason for appearance of pimples on her face?
(c) Why Salma experienced disproportionate growth of the body?
(d) What values do we get from this?
Answer:
(a) Regular face wash keeps the face clean and dry and helps to reduce the pimples.
(b) During adolescence, secretion of sweat glands and sebaceous glands increases leading to formation of acne and pimples.
(c) During adolescence, all parts of the body do not grow at the same rate. Sometimes the arms and legs or hands and feet of adolescents look oversized and out of proportion with the body.
(d) We must be self-aware, must take proper care and diet during the growing period, not get worried or lose our self-esteem.

In this page, we are providing Cell Structure and Functions Class 8 Extra Questions and Answers Science Chapter 8 pdf download. NCERT Extra Questions for Class 8 Science Chapter 8 Cell Structure and Functions with Answers will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 8 Extra Questions and Answers Cell Structure and Functions

Extra Questions for Class 8 Science Chapter 8 Cell Structure and Functions with Answers Solutions

Cell Structure and Functions Class 8 Extra Questions Very Short Answer Type

Question 1.
What is the basic, functional and structural unit of life?
Answer:
Cell

Question 2.
Which cell does not have nucleus?
Answer:
Red blood cell

Question 3.
What is the name of the organism which can be seen only with the help of microscope?
Answer:
Microorganisms

Question 4.
What are the organisms which are composed of many cells packed together called?
Answer:
Multicellular organisms

Question 5.
What is the name of the power house of the cell?
Answer:
Mitochondria

Question 6.
Name one example of prokaryotic cell.
Answer:
Blue-green algae

Question 7.
Amoeba and Paramecium belong to which category of organisms?
Answer:
Unicellular

Question 8.
Which instrument is used to observe cells?
Answer:
Micrbscope

Question 9.
Why we do not sense any pain when we cut nails and hair?
Answer:
Nails and hair are made up of dead cells.

Question 10.
What is the name of living substance present in cell?
Answer:
Protoplasm

Question 11.
What is the other name of cell membrane?
Answer:
Plasma membrane

Question 12.
What is the name of thread-like structure present in nucleoplasm?
Answer:
Chromatin

Question 13.
What is the name of cell which has a well-defined nucleus?
Answer:
Eukaryotic cell

Question 14.
Name the two types of cell.
Answer:
Prokaryotic cells and eukaryotic cells.

Cell Structure and Functions Class 8 Extra Questions Short Answer Type

Question 1.
What is the function of cell wall?
Answer:
Cell wall is a tough, rigid layer that surrounds some types of cells (plants and some bacterial cells). The major function of the cell wall is to provide rigidity, tensile strength, structural support, protection against mechanical stress and infection.

Question 2.
Name the parts of the nucleus and state its function.
Answer:
Nucleus consists of three main parts nuclear membrane, nucleoplasm and nucleolus. Nucleus plays an important role during cell division. It also controls the activities of the cell.

Question 3.
What is an organ?
Answer:
The structure that contains more than one type of tissues and is visible to the naked eyes are called organs.

Question 4.
What do you mean by unicellular and multicellular organisms?
Answer:
Organisms which consists of only one cell are called unicellular organisms while the organisms made up of more than one cell are called multicellular organisms.

Question 5.
Give a brief description of nucleus.
Answer:
Nucleus is a dense round body found in the centre of an animal cell and mostly on the periphery of the plant cell. The nucleus controls all the activities in a cell.

Question 6.
Name the following:
(i) Controls the function of a cell.
(ii) Selectively allows things to get in and out of the cell.
(iii) Transfer characters from parents to offsprings.
Answer:
(i) Nucleus
(ii) Cell membrane
(iii) Genes

Question 7.
What is nucleolus?
Answer:
A spherical body present at the centre of the nucleus is called the nucleolus.

Question 8.
What is endoplasmic reticulum?
Answer:
It is the system of complex folded network of membranous tubes which connects nuclear membrane with the plasma membrane. They allow movement of substances within the cell.

Question 9.
What are cell organelles?
Answer:
The tiny components present in the cytoplasm are called cell organelles.

Question 10.
What is cell membrane?
Answer:
The thin and delicate membrane surrounding the cell cytoplasm is called cell membrane.

Cell Structure and Functions Class 8 Extra Questions Long Answer Type

Question 1.
Differentiate between
(a) Cell wall and cell membrane
(b) Leucoplast and chloroplast
(c) Vacuole in a plant cell and an animal cell
(d) A tissue and an organ
Answer:
(a) Cell wall and cell membrane

(b) Leucoplast and chloroplast

(c) Vacuole in a plant cell and an animal cell

(d) A tissue and an organ

Question 2.
What are the main functional regions of a cell? Explain.
Answer:
Main functional regions of a cell are:

• Plasma membrane: This is the membrane which makes the outer boundary of the cells. It is very thin, delicate and selectively permeable.
• Cytoplasm: Cytoplasm is viscous, transparent jelly-like substance of the cell. It contains cell organelles.
• Nucleus: Nucleus controls the working of the cell. It is a dense oval body lying in the protoplasm of the cell.

Question3.
Define cell membrane and state its functions.
Answer:
Cell membrane or plasma membrane is a thin, delicate membrane surrounding the cytoplasm.
Following are the functions of cell membrane:

• It separates the cells from one another and also separates the cells from the surrounding medium.
• It gives a definite shape to the cell.
• Being porous, it allows the movement of substances from both inside and outside the cells.
• Its porous structure helps in regulating the movement of materials through the cells.

Question 4.
Define nucleus and state its major parts.
Answer:
Nucleus is a dense round body found in the centre of an animal cell and mostly on the periphery of the plant cell. The nucleus controls all the activities in the cell like digesting movement of substances within the cell. Nucleus also controls the process of cell division. This is the reason nucleus is also known as the ‘brain of the cell’.

Nucleus consists of four major parts. They are:

• Nuclear membrane
• Nucleoplasm
• Nucleolus
• Chromatin

Cell Structure and Functions Class 8 Extra Questions HOTS

Question 1.
Which organism is more efficient in its functioning unicellular or multicellular? Why?
Answer:
Multicellular organisms are more efficient in its functioning because labour is divided among the cells and have great capacity to survive than unicellular organisms.

Question 2.
What would happen if animals have cell wall?
Answer:
All parts of the animal would become rigid which will make their movement of limbs and body parts difficult.

Question 3.
Cells consist of many organelles, yet we do not call any of these organelles as structural and functional unit of living organisms. Explain.
Answer:
Organelles cannot function outside the cell as an independent unit. They can perform their functions only when they are within the living cells.

Question 4.
Why plant cells need cell walls?
Answer:
As plants cannot move, they need protection against variations in temperature, high wind speed, atmospheric moisture, etc.

Cell Structure and Functions Class 8 Extra Questions Value Based (VBQs)

Question 1.
In a cell, every cell organelle perform its own function. They coordinate the functions of cell.

(a) Can a cell work if any of its organelle stops working?
(b) What does a cell represent in a real life?
(c) What values do we get from the above paragraph?
Answer:
(a) Cell would not work if any of its organelle stops working.
(b) Cell represent our society where various people do their work to maintain it.
(c) We should perform our duty regularly and honestly for the betterment of the whole world.

Question 2.
Shyam being very inquisitive, didn’t listen to the teacher’s instruction properly. He took the thin layer of onion peel with a drop of water on the glass slide. He placed the coverslip on it and start observing the slide under a microscope. But he was unable to see the cells of onion peel properly.

(a) What do you think he might have forgotten?
(b) What is the function of a dye?
(c) What values do you get from the above incidence?
Answer:
(a) He might have forgotten using dye.
(b) Dye stains the cell and its component and make them visible.
(c) We must always follow teacher’s instruction. In laboratory we must not hurry and keep patience.

In this page, we are providing Conservation of Plants and Animal Class 8 Extra Questions and Answers Science Chapter 7 pdf download. NCERT Extra Questions for Class 8 Science Chapter 7 Conservation of Plants and Animal with Answers will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 7 Extra Questions and Answers Conservation of Plants and Animal

Extra Questions for Class 8 Science Chapter 7 Conservation of Plants and Animal with Answers Solutions

Conservation of Plants and Animal Class 8 Extra Questions Very Short Answer Type

Question 1.
What is sanctuary?
Answer:
An area where animals are protected from any disturbance to them and their habitat is called a – sanctuary.

Question 2.
Name the major threat to the survival of organism.
Answer:
Deforestation

Question 3.
Write the names of some parks and sanctuaries.
Answer:
Dudhwa National Park, Bharatpur Bird Sanctuary, Kaziranga National Park, Nelapattu Bird Sanctuary, etc.

Question 4.
Write two natural causes of deforestation.
Answer:

• Severe droughts
• Forest fires

Question 5.
Give examples of flora.
Answer:
Teak, sal, mango, jamun, arjun, etc.

Question 6.
Give examples of fauna.
Answer:
Elephant, tiger, wild bear, etc.

Question 7.
Name two endemic fauna.
Answer:
Giant squirrel, bison

Question 8.
Name some forest products.
Answer:
Paper, wood, timber, vegetables, fruits, rubber, etc.

Question 9.
What is the name of the reserved land used to protect biodiversity?
Answer:
Biosphere Reserve

Question 10.
Name the first Reserve Forest of India.
Answer:
Satpura National Park

Question 11.
Name products obtained from animals for which they are hunted.
Answer:
Skin, fur, horn, eggs, flesh, etc.

Question 12.
Does soil erosion affect the fertility of soil?
Answer:
Yes

Question 13.
List the names of some migratory birds.
Answer:

• Siberian crane
• Bar-headed goose
• Arctic tern
• Surkhab

Question 14.
Write the names of some extinct animals.
Answer:
Dodo, dinosaurs, mammoth, etc.

Question 15.
When was Project Tiger launched?
Answer:
April 1,1973

Question 16.
How many rock shelters are there in Pachmarhi Biosphere Reserve?
Answer:
55

Question 17.
Name two wildlife sanctuaries present in Pachmarhi Biosphere Reserve.
Answer:
Pachmarhi, Bori

Question 18.
What is the plantation of new plants called?
Answer:
Reforestation

Question 19.
What is a zoo?
Answer:
A place where animals receive protection is called a zoo.

Question 20.
Name one reason owing to which birds migrate.
Answer:
For breeding

Conservation of Plants and Animals Class 8 Extra Questions Short Answer Type

Question 1.
What do you mean by deforestation?
Answer:
The cutting of trees on a large scale is called deforestation.

Question 2.
Define national park.
Answer:
A national park is an area reserved for wildlife where they can freely use the habitats and natural resources.

Question 3.
What are flora?
Answer:
The plant species found in a particular area are called flora.

Question 4.
What are fauna?
Answer:
The animal species found in a particular area are called fauna.

Question 5.
What do you mean by species?
Answer:
Species is a group of population which are capable of interbreeding.

Question 6.
What is Satpura Tiger Reserve?
Answer:
It is a Project Tiger which was launched by the government in the country to protect the tigers.

Question 7.
What are endangered animals?
Answer:
The animals whose numbers are diminishing to such a level that they might face extinction are known as ‘endangered animals.’

Question 8.
Define ‘Red Data Book.’
Answer:
A book that keeps records of all the endangered plant and animal species is called a Red Data Book.

Question 9.
Define migratory birds.
Answer:
The birds which cover long distances to reach another land for some reasons are known as migratory birds.

Question 10.
Mention the causes of deforestation.
Answer:
The cause of deforestation could be:

• Forest fires
• Building houses, factories
• Severe droughts
• Using wood for some purposes
• Human encroachment and procuring land for cultivation

Question 11.
What do you mean by desertification?
Answer:
The conversion of fertile land into deserts is called desertification.

Question 12.
What is biodiversity?
Answer:
The diversity of plant and animal life in a particular habitat (or in the world as a whole) is called bio-diversity.

Question 13.
Define biosphere.
Answer:
Biosphere is that part of the earth in which living organisms exist or which supports biological diver-sity.

Question 14.
Define endemic species.
Answer:
The species of plants and animals which are found exclusively in a particular area are called endemic species.

Question 15.
Explain the term ecosystem.
Answer:
Ecosystem is a system formed by the interaction of a community of organisms with their physical environment.

Conservation of Plants and Animals Class 8 Extra Questions Long Answer Type

Question 1.
How does deforestation lead to frequent floods and droughts?
Answer:
Deforestation results in decreased water holding capacity of soil. This reduces the infiltration of water into the ground which causes floods. On the other hand, deforestation leads to higher level of carbon dioxide in the atmosphere which causes global warming. Scarcity of trees disturbs the water cycle and may reduce rainfall leading to droughts.

Question 2.
Explain how deforestation associated with global warming.
Answer:
Plants absorb carbon dioxide from the atmosphere for photosynthesis. Deforestation results in decreased number of trees leading to accumulation of carbon dioxide in the atmosphere. Carbon dioxide in the atmosphere traps heat rays reflected by the earth which results in global warming.

Question 3.
What do you mean by Biosphere Reserve?
Answer:
Biosphere Reserve is a large area of protected land for the conservation of wildlife, plant and animal resources and traditional life of the tribals living in that area.

Question 4.
How can we protect wildlife?
Answer:
Wildlife plays a significant role in maintaining a balance in the environment. They can be protected by establishing secured and protected area, which are restricted for human activities that are against the protection of wildlife. Cutting of trees, hunting, poaching are strictly banned there. Many of these areas are national parks and wildlife sanctuaries.

Question 5.
Why is the conservation of biodiversity important?
Answer:
Because of the following reasons, the conservation of biodiversity is important:

• It boosts tourism and thus, plays a significant role in enhancing the economy of the country.
• It maintains the fertility of soil.
• It helps in maintaining the ecological balance on the earth.
• Biodiversity is a rich source for the study of genetics and evolution.
• It helps in maintaining the weather by regulating climatic changes, rainfall, etc.

Question 6.
What are ‘rare species’? Give examples.
Answer:
Rare species are uncommon and scarce, that is to say, their population is very small. Major steps are to be taken for their conservation and protection so that they may not fall under the category of endangered or extinct species; e.g., wild buffalo, Bengal fox, gaur, marbled cat, etc.

Question 7.
What is Van Mahotsav? Who started it and when?
Answer:
Van Mahotsav is an annual tree-planting festival in India. This movement was initiated in the year 1950 by India’s Union Minister for Agriculture, Kulapati Dr K. M. Munshi. It has gained immense national importance and every year, millions of saplings are planted all across India in observation of the Van Mahotsav week. It is expected that every citizen of India has to plant a sapling in the Van Mahotsav week. It helps spread awareness amongst people about the harm caused by the cutting down of trees.

Conservation of Plants and Animals Class 8 Extra Questions HOTS

Question 1.
Why does it matter if a species go extinct?
Answer:
When a species go extinct, with it the whole food web get disturbed due to inter-relationship and interaction between organisms. The species of organisms which might have been dependent on the extinct species for food may also get extinct due to starvation until it get an alternate option. If the dependent species shift its choice of food on another species then there might be a competition for food with other species. Thus, in a nutshell, a extinct species affect the whole ecosystem.

Question 2.
Can a forest regenerate naturally in a short period of time?
Answer:
No, a forest takes a very long time for its growth and survival.

Question 3.
Mention the aim of Forest (Conservation) Act.
Answer:
Its aim were — conservation of natural forests and meeting the basic needs of the people living in or near the forests.

Question 4.
How are even small animals important in an ecosystem?
Answer:
Even very small animals form a part of food chain/food web in an ecosystem.

Question 5.
What is the affect of introduction of an exotic species to an ecosystem?
Answer:
Exotic species may affect the existence of local species either through predation or competition.

Conservation of Plants and Animals Class 8 Extra Questions Value Based (VBQs)

Question 1.
Many people in world find it status symbol of wearing and keeping leather clothes and leather articles with them. Even Shahtoosh shawls made of an endangered species of antelope are also in greater demand and highly priced.
(a) Do you think we must use leather items for just show off?
(b) What is endangered species?
(c) Can you name an extinct species which was exploited for its meat?
(d) What values of people are shown in above paragraph?
Answer:
(a) No
(b) A species which is at higher risk of getting extinct is known as endangered species.
(c) Dodo
(d) They are class conscious, selfish, irresponsible to nature, cruel, etc.

Question 2.
For centuries human activities such as hunting and encroachment have led to degradation of forests and extinction of many species of plants and animals. Government of India has taken many steps to conserve forests and wildlife. But this movement will not be a success without the involvement of all of us.
(a) What products are obtained from forests and wildlife?
(b) How can we help in conserving forest and wildlife?
(c) Can you name some organisation which are working against killing or poaching of animals?
(d) What values of human are shown here towards nature?
Answer:
(a) From forests: Wood for fire, timber, furniture, medicines, forage for livestock, gums, raisins, pa-pers, etc.
From wildlife: Horns, skin, leather, fur, ivory, meat, fin, etc.
(b)

• By saying ‘No’ to animal products we can at least reduce their hunting and poaching.
• By not cutting the trees and planting more saplings we can help in restoring the natural habitat of wild animals.
• By creating awareness among people about importance of forests and wildlife.

(c) World Wide Fund for Nature (WWF), International Fund for Animal Welfare (IFAW), World Society for the Protection of Animals (WSPA), etc.
(d) They are cruel, money-minded, selfish, reckless, etc.

In this page, we are providing Combustion and Flame Class 8 Extra Questions and Answers Science Chapter 6 pdf download. NCERT Extra Questions for Class 8 Science Chapter 6 Combustion and Flame with Answers will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 6 Extra Questions and Answers Combustion and Flame

Extra Questions for Class 8 Science Chapter 6 Combustion and Flame with Answers Solutions

Combustion and Flame Class 8 Extra Questions Very Short Answer Type

Question 1.
Name the most common fuel used in homes.
Answer:
Liquefied Petroleum Gas. (LPG)

Question 2.
Name the most common fire extinguisher.
Answer:
Water

Question 3.
What are the states in which a fuel may exist?
Answer:
A fual may exist in solid, liquid or gaseous state.

Question 4.
ame any two combustible substances.
Answer:
Charcoal, wood

Question 5.
Does magnesium produce heat and light during its combustion?
Answer:
Yes, it does.

Question 6.
What acts as a fuel for our body?
Answer:
Food

Question 7.
Give two examples of non-combustible substances.
Answer:
Water, sand

Question 8.
How are heat and light produced in the sun?
Answer:
In the sun, heat and light are produced by nuclear reactions.

Question 9.
Where were matchsticks first used?
Answer:
Egypt

Question 10.
What are the three essential requirements for combustion?
Answer:
Fuel, air (to supply oxygen) and heat (to raise the temperature of the fuel beyond the ignition temperature).

Question 11.
What is the ignition temperature of phosphorus?
Answer:
25°C

Question 12.
What is the colour of an LPG flame?
Answer:
Blue

Question 13.
What type of process is combustion?
Answer:
A chemical process

Question 14.
Name an ideal fuel.
Answer:
Compressed Natural Gas (CNG)

Question 15.
What is the composition of the head of a matchstick?
Answer:
Antimony trisulphide and potassium chlorate.

Question 16.
Which part of a flame does a goldsmith blow for melting gold and silver?
Answer:
The goldsmith blows the outermost zone of a flame for melting gold and silver.

Question 17.
What is the unit for expressing the calorific value of a fuel?
Answer:
Kilojoules per kilogram (kJ/kg)

Question 18.
Comparing the calorific values of coal and petrol, state which fuel is better.
Answer:
The calorific value of coal is about 25,000 – 33,000 kJ/kg, whereas that of petrol is 45,000 kJ/kg. Hence, petrol is better tuel.

Question 19.
What is deforestation?
Answer:
The cutting down of trees on a large scale is termed as deforestation.

Question 20.
Give any two examples of carbon fuels.
Answer:
Coal, petroleum

Combustion and Flame Class 8 Extra Questions Short Answer Type

Question 1.
What does magnesium burn to form?
Answer:
Magnesium burns to form magnesium oxide and produces heat and light.

Question 2.
What does coal produce during its combustion?
Answer:
Coal produces carbon dioxide, heat and light during its combustion.

Question 3.
What is combustion?
Answer:
Combustion is a chemical process in which a substance reacts with oxygen to give off heat.

Question 4.
Define the ignition temperature of a fuel.
Answer:
The lowest temperature at which a fuel catches fire is called its ignition temperature.

Question 5.
How does a matchstick catch fire?
Answer:
By rubbing a matchstick against a rough surface (friction), it attains its ignition temperature and thus catches fire.

Question 6.
Why is sodium kept immersed in kerosene?
Answer:
Sodium has very low ignition temperature, i.e., it catches fire on coming in contact with air, so it is kept in kerosene.

Question 7.
What are combustible and non-combustible substances?
Answer:
Substances which undergo combustion are said to be combustible, whereas non-combustible substances are those which don’t burn.

Question 8.
What are inflammable substances? Give examples.
Answer:
The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances; e.g., LPG, petrol, alcohol, etc.

Question 9.
What is rapid combustion?
Answer:
When a substance burns instantly and produces a huge amount of heat and light, the combustion is called rapid combustion; e.g., the instant burning of LPG in a gas stove.

Question 10.
Define spontaneous combustion.
Answer:
A type of combustion in which the substance suddenly catches fire without the supply of heat or friction externally is called spontaneous combustion; e.g., forest fires.

Question 11.
Define explosion.
Answer:
A type of combustion during which a huge amount of heat and light is evolved with a boom, along with the production of gas, is known as explosion; e.g., the exploding of fireworks, i.e., crackers, etc.

Question 12.
What is flame?
Answer:
Flame is a region where the burning or combustion of gaseous substances take place.

Question 13.
Define fuel.
Answer:
Those substances which provide energy on burning are called ‘fuels’; e.g., coal, petroleum, LPG, etc.

Question 14.
Give two examples each of solid fuels, liquid fuels and gaseous fuels.
Answer:

• Solid fuels – Wood, cow dung, etc.
• Liquid fuels – Kerosene, petrol, etc.
• Gaseous fuels – Hydrogen, methane, etc.

Question 15.
Give two examples of fuels that are used to generate electricity.
Answer:
Two examples of fuels that are used to generate electricity are petrochemicals and coal.

Question 16.
Define calorific value.
Answer:
The amount of heat produced on burning one kilogram of fuel completely is called its calorific value.

Question 17.
60 kg of fuel was completely burnt for an experiment. The amount of heat energy was found to be 1,80,000 kJ. Calculate the calorific value of the fuel.
Answer:
Amount of fuel burnt = 60 kg
Amount of heat produced = 1,80,000 kJ

∴ Calorific value of the fuel is 3,000 kJ/kg.

Question 18.
Define dark zone of a flame.
Answer:
The innermost zone of a flame around the wick is called its dark zone. It is the least hottest zone comparatively to other.

Question 19.
Name the colours of the flames of following substances:
Barium, arsenic, sodium, magnesium
Answer:

Question 20.
Mention any three characteristics of a good fuel.
Answer:
Any three characteristics of a good fuel are following:

• It has high calorific value.
• It is very easy to transport.
• It is cheap, affordable and economic.

Question 21.
What is global warming?
Answer:
An increase in the average temperature of the earth’s atmosphere, especially a sustained increase that causes climatic changes, is termed as ‘global warming’.

Combustion and Flame Class 8 Extra Questions Long Answer Type

Question 1.
Why isn’t hydrogen gas used as a domestic or industrial fuel, although it has a very high calorific value? State three reasons for the answer.
Answer:
Although hydrogen gas has a very high calorific value, it is not used as a domestic or industrial fuel due to the following reasons:

• It is expensive.
• It burns with an explosion.
• It is extremely inflammable, so it is risky to store and transport hydrogen.

Question 2.
Explain how water gets boiled in paper cup without burning it.
Answer:
When we heat the paper cup containing water, the heat given to it is rapidly transferred to water from the paper cup. The temperature of water goes on increasing until it attains its boiling point, and starts boiling. As, during this process, the heat is continuously being transferred to water; the paper cup does not attain its ignition temperature. Hence, it does not burn.

Question 3.
Why does a piece of paper burn with yellow flame? Give a reason.
Answer:
The inadequate supply of oxygen during the combustion of the piece of paper produces solid carbon particles that rise up in the flame. They become hot and glow to give off yellowish light. This makes the piece of paper burn with a yellowish flame.

Question 4.
It is observed at petrol pumps and airports, that hydrocarbon fire extinguishers are used, instead of soda-acid fire extinguisher. Give reasons why.
Answer:
At petrol pumps and airports, there is more probability of fire break out due to oil. In such situations, soda-acid fire extinguisher does not work as it contains water or uses water to take off fire by cooling down the place. Water being heavier than oil sinks to bottom and hence, fire does not get controlled. In such a case, hydrocarbon fire extinguisher is very useful, as it contains turkey red oil, which causes the foaming of carbon dioxide gas under pressure. The foam covers the surface of the burning substances and dispels the supply of air to control fire.

Question 5.
Explain complete combustion.
Answer:
This type of combustion involves complete burning of the combustible substance. No residue is left behind. Ash or smoke is not given off during or after this type of combustion. Mostly gases, such as hydrocarbons go through this form of combustion. On combustion, hydrocarbon produces carbon dioxide, water and heat.

Combustion and Flame Class 8 Extra Questions HOTS

Question 1.
There are three factors which supports burning. Fire extinguisher affects which factor?
Answer:
Fire extinguishers affect the supply of air.

Question 2.
Although wood has a very high calorific value, we still discourage its use as a fuel. Explain.
Answer:
Wood pollutes air very much and using wood as a fuel would also lead to deforestation on a large scale.
So we still discourage wood as a fuel.

Question 3.
Write in brief about the reasons of forest fires.
Answer:
Reasons of forest fires are:

• lightning if strikes forest trees or areas may lead to forest fires.
• human-caused fires.
• during extreme heat of summer, at some places dry grass catches fire. From this grass, very soon, it spreads to the whole forest.
• sparks from rock falls in a mountainous region can also be the reason of forest fires.
• volcanic eruption can also cause forest fires.

Question 4.
Can the process of cellular respiration be called combustion? Why?
Answer:
Yes. Cellular respiration is a set of metabolic reactions and processes that breaks large molecules into smaller one with the release of heat. So, this is a slow combustion reaction.

Question 5.
If you hold a piece of iron wire with a pair of tongs inside a candle flame or a Bunsen burner flame, what will you observe? Will it produce a flame?
Answer:
We will observe that the iron wire will become red hot and start glowing but it will not produce a flame as it is non flammable object.

Combustion and Flame Class 8 Extra Questions Value Based (VBQs)

Question 1.
Sourav was heating oil to fry potato chips. The cooking oil all of a sudden caught fire. He took water to pour on the fire to extinguish it. But meanwhile his mother came and switched off the gas and covered the wok completely with a plate.
(a) Do you think pouring water to the burning oil would have worked? Why?
(b) Do you think what Sourav’s mother had done is right? Why?
(c) Can you suggest other ways in which we can stop fire due to burning oil?
(d) What values of Sourav and Sourav’s mother are shown here?
Answer:
(a) No. As oil being lighter than water will come up and spill all around resulting in a major accident.

(b) Sourav’s mother had done right because she cut off the heat and oxygen supply from the oil. The fire will ultimately extinguish if it doesn’t get the required supply of air.
(c)

• By using excess of baking soda.
• By using fire extinguisher.
• By putting a completely wet towel on the pan to cut off the air supply.

(d) Sourav is immature in handling such situation but his mother is mature, wise with scientific tem-perament.

Question 2.
During a class discussion on ‘fuels for household’ Sarita suggested petrol. But her teacher said it is not a safe fuel for household activity and asked her to sit. Sarita wondered why petrol can’t be used as a fuel for household activity though its calorific value is high.
(a) Why petrol is not a safe fuel for household activity?
(b) What fuels do we use in our houses?
(cl What value of Sarita is shown here?
Answer:
(a) Petrol vapourises easily so it can lead to rapid combustion. Hence it is not safe as household fuel.
(b) We use LPG, kerosene and wax.
(c) Sarita has knowledge of fuel but she is little bit confused.