CBSE Class 10

HOTS Questions for Class 10 Science Chapter 9 Heredity and Evolution

These Solutions are part of HOTS Questions for Class 10 Science. Here we have given HOTS Questions for Class 10 Science Chapter 9 Heredity and Evolution

Question 1.
Observe the diagram carefully. What does it depict ? Identify the parts shown by lines.

Answer:
Reconstruction of fossil bird Archaeopteryx.

1. Claw
2. Free fingers
3. Beak
4. Teeth
5. Tail
6. Feathers

More Resources

• HOTS Questions for Class 10 Science
• NCERT Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• NCERT Exemplar Solutions for Class 10 Science
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Name the organism in which feathers appeared for the first time.
Answer:
Members of Dromaesaur family which were small dinosaurs.

Question 3.
Which one is the edible part in Kale, Kohlrabi, Broccoli, Brussel’s Sprout, Cabbage and Cauliflower ?
Answer:
Kale — Leaves,
Kohlrabi — Swollen stem,
Broccoli — Immature green flowers,
Brussel’s Sprout — Axillary buds,
Cabbage — Terminal bud,
Cauliflower — Immature inflorescence of sterile flowers.

Question 4.
Give an example where temperature determines the sex of the new bom.
Answer:

1. Chrysema picta (a turtle). Temperature above 33°C produces females and below 28°C males.
2. Agama agama (a lizard). High temperature produces males.

Question 5.
Name a recessive trait which is quite common in human beings.
Answer:
Blood group O (I°I°).

Question 6.
Why is variation beneficial for the species but not necessarily for the individual ? (CBSE Foreign 2010)
Answer:
Preadaptation is a variation which under normal conditions is of no advantage to the individual bearing it. However, it becomes highly useful in survival under changed environment, e.g, heat wave in temperate environment, insecticide or antibiotic resistance.

Hope given HOTS Questions for Class 10 Science Chapter 9 Heredity and Evolution are helpful to complete your science homework.

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NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce?

These Solutions are part of NCERT Exemplar Solutions for Class 10 Science. Here we have given NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce?

NCERT Exemplar Solutions for Class 10 Science Chapter 8 Short Answer Questions

Question 1.
In a bisexual flower, inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation.
Answer:
The open flowers are generally cross pollinated. Removal of stamens of a bisexual flower will not affect pollination of its intact pistil and formation of fruit.

More Resources

• NCERT Exemplar Solutions for Class 10 Science
• NCERT Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Can you consider cell division as a type of reproduction in unicellular organisms ? Give one reason.
Answer:
Yes. Cell division in a unicellular organism which produces two d&ughter cells, actually forms two daughter individuals.

Question 3.
What is a clone ? Why do offspring formed by asexual reproduction exhibit remarkable similarity ?
Answer:
Clone is an exact genetic replica of another individual. All the offspring formed from a parent through asexual reproduction are clones of one another as well as their parent. The remarkable similarity of asexually produced daughter individuals is due to genetic similarity as they possess exact copies of DNA of their parent.

Question 4.
Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes/DNAs.
(CCE 2014, CBSE Delhi 2017)
Answer:
The parents are diploid (2n) as each of them has two sets of chromosomes (DNAs). They form haploid (In) male and female gametes through the process of meiosis. The haploid gametes have one set of chromosomes (DNAs). During fertilization, one male gamete fuses with one female gamete. It restores the diploid (2n) chromosome/DNA number in the offspring that is formed from fusion product or zygote (2n).

Question 5.
Colonies of yeast fail to multiply in water but multiply in sugar solution. Give one reason for this.
Answer:
Yeast is heterotrophic. It obtains its nourishment from outside. Plain water cannot provide nourishment to yeast while sugar solution can do so. Therefore, Yeast multiplies in sugar solution and not in plain water.

Question 6.
Why does Bread Mould grow profusely on a moist slice of bread rather than on a dry slice of bread ?
Answer:
Growth of Bread Mould requires both water and nutrients. Dry slice of bread contains nutrients but no water. Therefore, Bread Mould does not grow over it. Moist slice possesses both water and nutrients. Hence, Bread Mould grows over it.

Question 7.
Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Answer:
Variations appear in the progeny of sexually reproducing organisms due to

1. Random separation and coming together of chromosomes during gamete formation and gamete fusion
2. Crossing over and mutations.
3. Coming together of chromosomes of the parents.

Question 8.
Would a Planaria cut vertically into two halves regenerate into two individuals ?
Answer:
Yes. Each piece of Planaria is able to grow the missing parts and form the complete organism.

Question 9.
Correlate the number of chromosomes with the size of the organism and answer the following questions :
(a) Do larger organisms have more number of chromosomes/cell ?
(b) Can organism with fewer chromosomes reproduce more easily than organism with more number of chromosomes ?
(c) More the number of chromosomes/cell, greater is the DNA content. Justify.
Answer:
(a) No. There is no correlation between chromosome number and size of the individual.
(b) No. Chromosome number does not affect reproduction.
(c) Yes. Each chromosome represents a single duplex of DNA. More chromosomes means more DNA.

Question 10.
In Tobacco, male gametes have 24 chromosomes.
(a) What is the number of chromosomes in the female gamete ?
(b) What is the number of chromosomes in the zygote ?
Answer:
(a) 24
(b) 48.

Question 11.
Why cannot fertilization take place in flowers if pollination does not occur ?
Answer:
Pollination is essential for bringing the male gametes. In the absence of pollination, there will be no male gamete to perform fertilization.

Question 12.
Is the chromosome number of zygote, emboryonal cells and adult of a particular organism always constant ? How is the constancy maintained in these three stages ?
Answer:
Zygote is the first diploid structure. It undergoes mitotic divisions to form embryonal cells. Embryonal cells further divide by mitosis to form the adult. Mitosis maintains the same chromosome number in the daughter cells.

Question 13.
Where is the zygote located in the flower after fertilization ?
Answer:
Zygote is the fertilized oosphere which occurs in the embryo sac present inside an ovule located in the ovary part of the pistil.

Question 14.
Reproduction is linked to stability of population of a species. Justify the statement.
Answer:
Reproduction maintains the size and composition of population of a species by regularly adding new individuals for replacing the ones getting killed due to ageing, disease or predation. It also adds variations that allow the individuals to adapt to changing environment.

Question 15.
How are general growth and sexual maturation different from each other ?
Answer:
General growth is the growth of an individual in size, height, shape, weight, etc. Sexual maturation is a set of changes in body of an individual that enable one to take part in reproduction, e.g., maturation of gonads, genitalia and other accessory structures. In human beings, beginning of sexual maturation is indicated by puberty changes like cracking of voice, new hair pattern, development of breast in female, etc.

Question 16.
Trace the path of sperm during ejaculation and mention the glands and their function associated with the male reproductive system.
Answer:
Ejaculated sperms are the ones which are stored in epididymes. They are formed regularly in seminiferous tubules from where they pass through vasa efferentia into epididymes. At the time of ejaculation, the sperms are first pushed through vasa deferentia, enter ejaculatory duct where they receive secretion of seminal vesicles and then urinogenital duct where the secretion of prostate gland is poured to form semen. The urinogenital duct is lubricated by secretion of a pair of Cowper’s glands (bulbourethral glands).
Secretion of Seminal Vesicles. Nourishment, activation and providing fluid medium for sperm transport.
Secretion of Prostates Gland. Motility of Sperms.

Question 17.
What changes are observed in the uterus if fertilization does not occur ? (CBSE Delhi 2017)
Answer:
Glands present in the mucosa of uterine endometrium begin to degenerate. This sloughs off the endometrial lining, releasing a lot of mucus and blood. It is called menstruation. Menstruation lasts for 3-5 days.

Question 18.
What changes are observed in the uterus subsequent to implantation of young embryo ? (CBSE Delhi 2017)
Answer:
Endometrium thickens, becomes glandular and highly vascular. The contact region between embryo and uterine wall grows into placenta. Placenta helps the embryo in obtaining nourishment and oxygen from blood sinuses of the uterus. It also helps in transfer of wastes from embryo to the blood of the mother.

Question 19.
What are the benefits of using mechanical barriers during sexual act ?
Answer:

1. Prevention of Pregnancy : Mechanical barriers (e.g., Condoms, diaphragms) prevent the passage of sperms into the genital tract of the female. Consequently, pregnancy does not occur.
2. Non-transmission of Infections: There is no transfer of venereal diseases from the infected partner to the non-infected partner.

Question 20.
In the female reproductive system, name the parts that are involved in
(a) Production of egg.
(b) Site of fertilization
(c) Site of implantation
(d) Entry of sperms.
Answer:
(a) Production of Egg: Ovary
(b) Site of Fertilization: Ampulla part of fallopian tube.
(c) Site of Implantation: Uterus.
(d) Entry of Sperms: Vagina.

Question 21.
What would be the ratio of chromosome number between an egg and its zygote ? How is the sperm genetically different from the egg ?
Answer:
Chromosome Number in Egg and Zygote. 1 : 2
Genetic Difference between Sperm and Egg. Sperms are genetically of two types, X-containing and Y-containing. Eggs are always of one type, X-containing.

NCERT Exemplar Solutions for Class 10 Science Chapter 8 Long Answer Questions

Question 22.
Why are budding, fragmentation and regeneration all considered as asexual types of reproduction ? With neat diagrams, explain the process of regeneration in Planaria.
Answer:
(a) Asexual Reproduction: Budding, fragmentation and regeneration are all considered to be modes of asexual reproduction as they involve formation of new individuals from single parents without fertilization or fusion of gametes.
(b) Regeneration in Planaria:

Question 23.
Write two points of differences between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.
Answer:
(a) Differences between Asexual and Sexual Reproduction

(b) Development of Variation in Sexual Reproduction:
Sexual reproduction produces a number of variations in the population due to

1. Chance separation of chromosomes at the time of meiosis.
2. Crossing over during meiosis.
3. Chance combination of chromosomes during fertilization. It produces a unique combination of variations already accumulated by each individual in its DNA obtained from its parents,
4. Mutations or defective DNA replication.

Question 24.
Distinguish between pollination and fertilization. Mention the site and product of fertilization in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.
Answer:
(a) Differences between Pollination and Fertilization

(b)

1. Site of Fertilization. Embryo sac in ovule.
2. Product of Fertilization. Zygote, Primary endosperm cell.

(c)

Question 25.
Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.
Answer:
Differences between Gamete and Zygote

Role of Gamete. Gamete is sex or germ cell which is specialized to take part in sexual reproduction. There are two types of gametes, male and female. Each of them carries one set of chromosomes which are randomly obtained from its parent. Fusion of male gamete with a female gamete produces a zygote.
Role of Zygote. It is the first’cell of new generation. Zygote develops into embryo that later forms the new individual.

Question 26.
Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower.
Answer:
(a)

(b) Male Gamete Forming Part. Pollen grain, produced in anther of stamen.
Female Gamete Forming Part. Embryo sac developed inside ovule of ovary part of pistil.

Question 27.
What is placenta ? Mention its role during pregnancy. (CCE 2011, 2014)
Answer:
Placenta: It is a special double layered, spongy tissue connection between the foetus and uternine wall found in pregnant females. It has finger-like outgrowths or villi which are in contact with blood sinuses present in the uterine wall.
Role:

1. Attachment: Placenta attaches the foetus to uterine wall.
2. Villi: Placenta has finger-like outgrowths or villi which develop a large surface area for fixation and absorption.
3. Nutrients: Placenta picks up nutrients from mother’s blood and passes it to the blood of the foetus.
4. Waste Products: Waste products produced by the foetus passes out through the placenta into mother’s blood.
5. Gases: Foetus obtains oxygen supply from mother’s blood and eliminates carbon dioxide through placenta.

Question 28.
What are the various ways to avoid pregnancy ? Elaborate any one method.
Answer:
(a) Methods to Avoid Pregnancy: Prevention of pregnancy is called contraception. The techniques used in preventing the occurrence of pregnancy are called contraceptive devices.
(b) Mechanical Barrier Methods of Contraception:

1. Mechanical Barriers like condoms, cervical cap, diaphragm.
2. Oral Contraceptives or oral pills like Mala D, Saheli
3. Intrauterine Contraceptive Devices (IUCD) like loop, bow, Cu-T.
4. Surgical Methods like vasectomy in males and tubectomy in females.

Question 29.
Flow does fertilization take place ? Fertilization occurs once in a month. Comment.
Answer:
In human beings, fertilization is internal. It can occur within 2-3 days of ovulation (between 14th and 16th day of menstrual cycle). Fertilization generally takes place in ampulla (ampulla-isthmus border) part of fallopian tube where ovum rests for several hours after entry into oviduct. The sperms have to reach there. Sperms deposited in the vagina reach there partly by their own movement and partly by local movements of reproductive tract. Both sperms and eggs are viable for 24-48 hours. A sperm reaching the surface of ovum, dissolves its covering and passes its head and middle part into it. It results in fertilization and formation of zygote.
Fertilization only once in a Month. A single ovum is released by female roughly in the middle of menstrual cycle which has a span of 4 weeks. Therefore, fertilization can occur only once in a month.

Question 30.
Reproduction is essentially a phenomenon that is not for survival of individual but for the stability of a species. Justify. Reproduction is not essential for survival of the individual.
Answer:
Survival of the individual depends upon input of nutrients and energy and elimination of wastes. Reproduction has ho role in these. It is, however, essential for the stability and survival of the species. Reproduction takes part in
(a) Perpetuation of Species: Perpetuation or continuation of species.
(b) Replacement: Replacement of dead individuals and maintaining the organisation in population.
(c) Population Characteristics:

1. Education: There is an inverse ratio between education and population growth.
2. Population Education: It is imparting knowledge to public about the effects of excessive population, advantages of small families and means to achieve it.
3. Marriageable Age: Number of births is reduced if young persons marry late. Gainful employment and higher social status of women also reduce birth rate.

(d) Variations:
Variations are differences found in morphological, physiological and other traits of individuals belonging to the same organism, race or family. They develop due to

1. Faulty DNA replication
2. Crossing over
3. Chance separation of chromosomes during meiosis and chance combination during fertilization. Variations are highly important.

(e) Absence of Variations: Due to absence of variations, asexually reproduced organisms are unable to adapt themselves to changes in the environment.

Question 31.
Describe sexually transmitted diseases and mention the ways to prevent them.
Answer:
It is a group of infections caused by different types of pathogens that are transmitted by sexual contact between a healthy person and an infected person. The sexually transmitted diseases are also called venereal diseases (VDs). Some 30 different types of STDs are known.

1. It is caused by bacterium Neisseria gonorrhoeae. Gonorrhoea spreads through sexual contact, common toilets and under clothes. Incubation period is 2-5 days. Bacterium resides in genital tubes. It causes pus containing discharge, pain around genitalia and burning sensation during urination. Effective medicine is ampicillin.
2. The disease is caused by corkscrew like bacterium Treponema pallidum. It spreads through sexual contact and from mother to infants. Incubation periods is 3-5 weeks, Painless ulcer on genitalia and swelling of lymph glands occur in first stage. In second stage skin lesions, rashes and hair loss occur. Tertiary stage is characterised by chronic ulcers and damage to vital organs. Effective medicine is tetracycline.
3. Genital Warts: The disease is due to Human Papilloma virus (HPV). Hard benign outgrowths called warts appear over external genitalia and perianal area. In women infection may enter vagina and cervix causing acute pain. Cryosurgery and Podophyllum preparations are effective.
4. AIDS (Acquired Immune Deficiency Syndrome): It is caused by human immunodeficiency virus or HIV. The virus is transmitted through sexual contact, blood contact (as using common needles, syringes, razors, transfusion) and placenta (mother to foetus). Incubation period is generally 27-28 months but symptoms may appear early. Count of T-helper cells becomes low, 200/ml or less. There is headache, rashes, nausea, pharyngitis and fever. Immunity is drastically reduced so that many infections (opportunistic infections) begin to appear. A proper treatment has not yet been discovered. ART (antiretrovirus treatment) is given to patients to reduce the effect of infection.

Hope given NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce? are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

Value Based Questions in Science for Class 10 Chapter 8 How do Organisms Reproduce?

These Solutions are part of Value Based Questions in Science for Class 10. Here we have given Value Based Questions in Science for Class 10 Chapter 8 How do Organisms Reproduce?

Question 1.
A classmate of yours has a pus containing discharge, pain around genitalia and burning sensation during urination. What disease he is suffering from. How has he caught the disease ? How will you help your classmate ? What precautions are required not to get the repeat of the disease ?
Gonorrhoea. Gonorrhoea is commonly a sexually transmitted disease. My classmate has caught the disease despite his being not involved sexually with any one. The other possibility is that he is using common underwears. It is also not possible as he is the lone kid of the family. No body else in his family has this disease. The last possibility is that he has caught the disease by using toilets at his relative’s home or in the school.
Clean and hygienic toilets can prevent the occurrence of this and many other diseases.

More Resources

• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science
• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Surbhi and Mukesh are a young couple married only four years ago. They have two children. How will you convince the couple not to have any more child ? What guidelines will you give to the couple ?
Answer:
Conviction: I will tell the couple that :

1. A safe, satisfying reproductive health is possible only when the number of children is small.
2. Small number of children helps in enjoying the family life better both at home and outside.
3. The children can be reared with better resources. They can be properly educated and settled in life.
4. The couple can also save and plan properly for their post retirement life.

Guidelines: The couple should start using contraceptive device(s) that suit them best, may be oral pills, IUCD or condom.

Question 3.
Seeing the different colours of Bougainvillea growing in the corner of school campus the Principal suggested that the boundary of the whole campus be decorated with the plant.
How you and your classmates will perform this task ?
Answer:

1. The first task is to select the colour scheme that will best suit the campus boundary wall,
2. How much space is to be given to each colour,
3. Digging and properly watering the soil along the boundary wall but leaving a space of 25-30 cm from the wall for preventing any damage to it and keeping a narrow pathway for movement of the gardener,
4. Preparing stem cuttings of 25-30 cm length from one year old branches.
5. Fixing the cuttings in the soil in their natural position at a distance of about 30 cm from one another in 3-4 rows as per plan,
6. Regular but well spaced watering of the cuttings,
7. The cuttings will become independent plants within 2-3 months.

Question 4.
You have read in newspapers that sex ratio in many parts of the country has gone down to less than 900:1000. What does this mean ? What is the reason behind it ? How can you contribute in retrieving the situation ?
Answer:
The ratio 900 : 1000 is called sex ratio. It indicates that there are 900 females to 1000 males. This is not a healthy sign for the society. A number of males will not be able to find suitable brides leading to several types of social problems.
The reason behind this decline in sex ratio is the availability of sex determining devices for the foetus and carrying out abortion in case of female foetus.
Retrieving Situation :

1. Organising rallies against female foeticide
2. Organising vigilance group to find out the centres where sex of the foetus is being determined and reporting the same to the health authorities.

Our government lauches compaigns to provide information about AIDS prevention, testing and treatment by putting posters, conducting radio shows and using other agencies of advertisements.

Question 5.
(a) To which category of diseases AIDS belong ? Name its caustive organism.
(b) Which kind of value is government trying to develop in the citizens by conducting the above kind of programmes. (Sample Paper 2017-18)
Answer:
(a) AIDS is a sexually transmitted disease (STD) which is also contracted through blood (using common syringes, needles, razors) and placenta.
Causative Agent: Virus— Human Immuno deficiency Virus or HIV.
(b) Values:

1. Government is trying to save the citizens from the debilitating and fatal disease by telling every citizen through all means of communication how the disease spreads and what are the ways to prevent it.
2. Government is also informing the citizens about the institutes where free testing is available and asking the patients to get registered with the treatment centres for free medicines.
3. The public is also informed not to shun the AIDS patient as the disease does not spread by mere contact. It will reduce the trauma being suffered by the patient.

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HOTS Questions for Class 10 Science Chapter 8 How do Organisms Reproduce?

These Solutions are part of HOTS Questions for Class 10 Science. Here we have given HOTS Questions for Class 10 Science Chapter 8 How do Organisms Reproduce?

Question 1.
What does the diagram depict

Answer:
Tubectomy or cutting and ligating the oviducts of a women.

More Resources

• HOTS Questions for Class 10 Science
• NCERT Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• NCERT Exemplar Solutions for Class 10 Science
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Identify the material shown in the diagram.

Answer:
Yeast showing budding.
A – Parent
B – bud

Question 3.
How does Bryophyllum multiply vegetatively ?
Answer:
By leaves which bear adventitious buds in their marginal notches.

Question 4.
When is menstruation absent in a lady ?
Answer:
Before menarche, after menopause and during pregnancy.

Question 5.
What is normal fertility period ?
Answer:
14th to 16th day of menstrual cycle.

Question 6.
(a) Name the parts labelled A, B, C, D and E.

(b) Where do the following functions occur l

1. Production of an egg
2. Fertilization
3. Implantation of zygote.

(c) What happens to the lining of uterus ?

1. Before release of a fertilized egg
2. If no fertilization occurs. (C.B.S.E. Delhi 2008 C)

Answer:
(a)

1. A-Fallopian tube
2. B-Ovary
3. C-Uterus
4. D-Cervix
5. E-Vagina

(b)

1. Ovary
2. Fallopian tube
3. Uterus

(c)

1. Repair and growth of endometrium followed by its thickening and development of glands.
2. Breakdown of endometerial lining and rupturing of its blood vessels producing menstural flow.

Hope given HOTS Questions for Class 10 Science Chapter 8 How do Organisms Reproduce? are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

NCERT Exemplar Solutions for Class 10 Science Chapter 7 Control and Coordination

These Solutions are part of NCERT Exemplar Solutions for Class 10 Science. Here we have given NCERT Exemplar Solutions for Class 10 Science Chapter 7 Control and Coordination

NCERT Exemplar Solutions for Class 10 Science Chapter 7 Short Answer Questions

Question 1.

1. Label the parts a, b, c and d and show the direction of electrical signals in the figure. (CBSE 2010)
   
2. Draw the figure shown here and label motor neuron, relay neuron and spinal cord. What is the name of this connection ?
   (CCE 2011)

More Resources

• NCERT Exemplar Solutions for Class 10 Science
• NCERT Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science
• Previous Year Question Papers for CBSE Class 10 Science

Answer:

1. a – Sensory neuron.
   b – Spinal cord (CNS).
   c – Mortor neuron.
   d – Effector (muscle in arm)
2. Name — Reflex arc.
   Direction :
   1. Receptor (hand) to spinal cord through sensory neuron,
   2. Sensory neuron to motor neuron through Spinal cord to effector through motor neuron.

Question 2.
Name the plant hormone responsible for the following :
(a) Elongation of cells
(b) Growth of stem
(c) Promotion of cell division
(d) Falling of senescent leaves.
Answer:
(a) Elongation of Cells. Auxin.
(b) Growth of Stem. Gibberellin.
(c) Promotion of Cell Division. Cytokinin.
(d) Falling of Senescent Leaves. Abscisic acid.

Question 3.
Label the endocrine glands in the figure

Answer:
a – Pineal gland.
b – Pituitary gland.
c – Thyroid
d – Thymus.

Question 4.
In the figures (a), (b) and (c) which appears more accurate and why ?

Answer:
Figure (a) is more accurate as it shows appropriate response of both shoot and root to the vector of gravity. Shoot is negatively geotropic. It, therefore, bends upwardly. Root is positively geotropic. It, therefore, bends downwardly.

Question 5.
Label the parts of a neuron shown in the figure.

Answer:
a – Dendrite.
b – Cyton (Cell body).
c – Axon.
d – Axon terminal (bouton).

Question 6.
Match the terms of column A with those of column B.

Answer:
a – IIi,
b — iv,
c — i,
d — ii.

Question 7.
What is a tropic movement ? Explain with an example. (CCE 2011)
Answer:
Tropic Movement: It is directional paratonie growth movement of curvature in which direction of movement is determined by the direction of the stimulus. They mostly occur in cylindrical organs. Growth response occurs due to differences in the distribution of auxin.
Example. On unidirectional exposure to light, shoots bend towards the source of light (positive phototropism) while roots may bend away from the source of light (negative phototropism).

Question 8.
What will happen if intake of iodine in our diet is low ?
Answer:

1. Low intake of iodine will affect production of thyroxine. Reduced thyroxine reduces metabolism of protein, carbohydrate and fat. Physical activity and consumption of energy are impaired.
2. With continued reduced intake of iodine, thyroid gland enlarges (in order to produce more thyroxine). It results in swelling of neck called goitre.

Question 9.
What happens at the synapse between the neurons ?

                                                   Or

State the events in sequence that take place when an electrical impulse travels from a dendritic tip of a nerve cell to another nerve cell. (CCE 2011, 2012, 2013)
Answer:
At synapse, axon terminal is expanded to form presynaptic knob. The dendrite terminal that lies close to it is slightly broadened and depreseed to form post-synaptic depression. A fluid filled narrow space, called synaptic cleft, occurs between the two. When an impulse reaches the presynaptic knob, it stimulates the release of neurotransmitter into synaptic cleft. Neurotransmitter comes in contact with chemoreceptor sites of the membrane of postsynaptic depression. This generates an electrochemical signal or impulse in the dendrite part of second neuron.

Question 10.
Answer the following :
(a) Which hormone is responsible for the changes noticed in female at puberty ?
(b) Dwarfism results due to deficiency of which hormone ?
(c) Blood sugar level rises due to deficiency of which hormone ?
(d) Iodine is necessary for synthesis of which hormone ?
Answer:
(a) Puberty Changes in Females. Oestrogen.
(b) Dwarfism. Growth hormone.
(c) Blood Sugar. Insulin.
(d) Iodine Hormone. Thyroxine

Question 11.
Answer the following :
(a) Name the endocrine gland associated with brain.
(b) Which gland secrets digestive enzymes as well as hormones ?
(c) Name the endocrine gland associated with kidney.
(d) Which endocrine gland is present in males but not in females ?
Answer:
(a) Endocrine Gland Associated with Brain. Pituitary.
(b) Gland with Digestive Enzymes and Hormones. Pancreas.
(c) Endocrine Gland Associated with Kidneys. Adrenal glands.
(d) Endocrine Gland in Males only. Testis.

NCERT Exemplar Solutions for Class 10 Science Chapter 7 Long Answer Questions

Question 12.
Draw the structure of a neuron and explain its function. (CCE 2011)
Answer:

Functions:

1. Dendrites: Picking up sensations and transmitting the same to cell body.
2. Cell Body:
   1. Sustaining structure and function of dendrites and axon,
   2. Functioning as passage¬way for transmission of sensation or impulse to axon.
3. Axon: Carrying impulse to another neuron, muscle, gland and organ. A single impulse can be transmitted to several structures with the help of axon terminals.

Question 13.
What are the major parts of the brain ? Mention the function of different parts.
Answer:
Major Parts of Brain
Fore-Brain: Olfactory lobes (2), Cerebral hemispheres (2) or cerebrum, Diencephalon.
Mid-Brain: Cerebral peduncles, Corpora quadrigemina.
Hind Brain: Pons, Cerebellum, Medulla oblongata.
Functions

1. Olfactory Lobes: Receive sensation of smell from olfactory epithelium and relay the same to temporal lobes of cerebral hemispheres.
2. Cerebral Hemispheres:
   1. Frontal Lobes: Centres of intelligence, control of movements and facial muscles, speech.
   2. Parietal Lobes: Taste and cutaneous sensations with some components of speech.
   3. Temporal Lobes: Hearing, smell, recall of audiovisual memory, some components of speech.
   4. Occipital Lobes: Sight.
3. Diencephalon: Hypothalamus part regulates activity of smooth muscles and functions as control centre for hunger, thirst, fatigue, sleep, sweating, temperature and emotions. Pituitary gland and pineal gland are components of diencephalon.
4. Corpora Quadrigemina: Superior – sight reflexes. Inferior – auditory reflexes.
5. Cerebellum: Controls posture and equilibrium.
6. Pons: Part of respiratory centre.
7. Medulla Oblongata: Centre for reflexes, blood pressure, heart beat, breathing.

Question 14.
What constitutes the central and peripheral nervous systems ? How are the components of central nervous system protected?
(CCE 2012)
Answer:
Central Nervous System (CNS): It is hollowed part of nervous system that lies along the mid-dorsal part of the body. It has two parts, brain (located in the head) and spinal cord (located in the trunk).
Peripheral Nervous System (PNS): It is soild lateral part of nervous system that develops from CNS and connects different parts of the body with CNS. Peripheral nervous system has two components, voluntary and involuntary. Voluntary peripheral nerous system is under the control of will. It consists of cranial nerves from brain and spinal nerves from spinal cord. Involuntary peripheral nervous system works independent of will. It develops from some cranial and spinal nerves. Involuntary peripheral nervous system is also called autonomic nervous system. It has two parts, sympathetic (for emergency) and parasympathetic (for moderation). They control the functioning of various internal body parts.
Protection of Brain: Brain box or Cranium, meninges and cerebrospinal fluid.
Protection of Spinal Cord: Vertebral Column, meninges and cerebrospinal fluid.

Question 15.
Mention one function for each of these hormones.
(a) Thyroxine
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone. (CCE 2010, 2013, 2015)
Answer:
(a) Thyroxine: Regulates metabolism of carbohydrates, fats and proteins, release of energy and body activity.
(b) Insulin: Regulates blood glucose by its absorption in liver, muscles (for formation of glycogen) and individual cells (for metabolic activity).
(c) Adrenaline: For meeting an emergency by increasing heart rate and supply of blood to various concerned organs.
(d) Growth Hormone (GH) or Somatotrophic Hormone: Regulates growth and development of the body through anabolic activity for growth of bones, muscles and visceral organs.
(e) Testosterone (Male Sex Hormone): Controls changes in body associated with puberty in males (beard, moustache, low pitch voice, increased growth of bones and muscles).

Question 16.
Name the various plant hormones. Also give their physiological effects on plant growth and development. (CCE 2016)
Answer:
Five types — auxin, gibberelin, cytokinin, ethylene and abscisic acid.
Auxin: Cell enlargement, root formation, apical dominance, inhibition of abscission, fruit growth.
Gibberellin: Growth in stem and leaves, higher fruit yield, overcoming dormancy.
Cytokinin: Essential for cell division, differentiation, prevention of senescence and overcoming apical dominance.
Ethylene: Promotes transverse growth, fruit ripening and overcoming dormancy of some parts.
Abscisic Acid (ABA): Induces dormancy, senescence and abscission, checking excessive activity of growth promoting hormones, closure of stomata under water stress.

Question 17.
What are reflex actions ? Give two examples. Explain a reflex arc.
Answer:
Definition: Reflex actions seem to have evolved quite early in the physiology of animals when complex neuron network for processing had not been evolved. Even after evolution of processing centres, reflex actions have continued to persist because of their more efficiency for quick responses.
Two Examples:

1. On being pricked or coming in contact with hot surface, hand is withdrawn even before pain is perceived (by brain),
2. Wider openin0 of pupil in dim light and its narrowing in strong light.
   

Question 18.
“Nervous and hormonal systems together perform the function of control and coordination in human being.” Justify the statement.
Answer:
Both nervous system and hormonal (or endocrine) system are involved in control, regulation and coordination of body parts. Nervous system is connected to receptors of all senses. Information obtained from sensory organs is passed rapidly to CNS for interpretation.
On the basis of interpretation, a message is sent to effector organ or organs (muscles, glands, etc.). The rate of information or impulse transfer is very high, some 100m/sec. Every action and activity is well coordinated as the information is sent to all the regions required for that action. The action can be voluntary (under the will) or involuntary. Passage of food in the alimentary canal is due to an involuntary movement of alimentary canal called peristalsis. Picking up food and placing it inside the mouth is a voluntary movement. Both these movements are highly coordinated by nervous system.
Nervous system is also connected with the functioning of endocrine or hormonal system. The endocrine system functions at the biochemical level while nervous system functions at the physical and physiological level. For their functioning endocrine glands pour their secretion into blood which transports them to all parts of the body. Target cells have receptors for picking up the hormones and working as per hormonal stimulus. There is a feedback system which determines the requirement of hormones and the activity of endocrine glands. Other stimuli are also involved for coordinated functioning. Presence of food in the stomach stimulates its wall to secrete hormone gastrin. Gastrin stimulates gastric glands to pour gastric juice over the food. As the partially digested food passes into duodenum, the latter forms hormone secretin which induces passage of bile and pancreatic juice into duodenum.
Joint working of both the systems is observed during an emergency. Both sympathetic nervous system and adrenal glands prepare the body for meeting the emergency. There is higher rate of heart beat, more blood supply to cardiac and skeletal muscles and higher rate of breathing for quicker oxygenation of blood.

Question 19.
How does chemical co-ordination take place in animals ?
Answer:
In animals, chemical coordination is achieved through the agency of hormones which function as chemical messengers or informational molecules. Hormones are secreted by ductless glands in response to specific conditions or nervous stimulation. Timing and amount of a hormone released are regulated by feed-back mechanism. After a meal, sugar level of blood rises. It is detected by pancreas. Pancreas responds by producing hormone insulin from (3-cells of islets of Langerhans. Insulin causes glucose to be absorbed by all cells as well as get stored in liver and muscles in the form of glycogen. As the level of glucose falls in blood, insulin secretion is reduced.

Question 20.
Why the flow of signals in a synapse is from axonal end of one neuron to dendrite end of another neuron but not the reverse ?
Answer:
As the electrical impulse reaches the axon terminal in the region of axon-dendrite synapse, it stimulates the exocytosis of vesicles containing neurotransmitter (e.g. acetylcholine). Neurotransmitter attaches to the chemoreceptor sites of the membrane covering the dendrite end of synapse. It creates a new impulse that travels through cell body and axon of the second neuron. At synapse, the axon end does not contain any chemoreceptor sites so that reverse flow of electrochemical impulses is not possible.

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