NCERT Solutions Class 10 for Science Chapter 8 How do Organisms Reproduce : In this post, we will share with you all the detailed NCERT Solutions of Class 10 Science Chapter 8 How do Organisms Reproduce. This will contain both in-text and back-exercise questions for Science and Social Science, and all exercise questions for Mathematics. For all school and board level examinations, doing all the NCERT Questions is a must.

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Class 10 Science Chapter 8 How do Organisms Reproduce

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In-Text Questions (Page 128)

Question 1:
What is the importance of DNA copying in reproduction?

Answer 1:
DNA – Deoxyribonucleic acid is the genetic material that is present in the cells of all organisms. DNA carries genetic information from one generation to the other and this helps in producing organisms of its own types. DNA copying is a must for inheriting the traits from parents. Any variations in DNA copying will give rise to origin of new species.

Question 2:
Why is the variation beneficial to the species but not necessarily for the individual?

Answer 2:
The reason why the variation is beneficial to the species than individuals is because sometimes the climatic changes have a drastic effect on the species, which makes their survival difficult. For examples, if the temperature of the water body increases, then there might be certain species of microorganisms which might die. This may result in disturbance in the environment. So, variation is beneficial to species and not for the individuals.

In-Text Questions (Page 133)

Question 1:
How does binary fission differ from multiple fission?

Answer 1:
When a single cell divides into two equal halves, it is known as binary fission. Bacteria and amoeba are the examples of binary fission.
When a single cell divides into multiple daughter cells at the same time, it is known as multiple fission. Algae and sporozoans are the examples of multiple fission.

Question 2:
How will an organism be benefited if it reproduces through spores?

Answer 2:
An organism is benefited by reproducing through the spores because spores are surrounded by a thick layer which protects them in adverse conditions. When the favourable conditions occur, these spores start to grow again. In this way they are successfully live in unfavourable conditions.

Question 3:
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration ?

Answer 3:
In complex multicellular organisms, specialised cells make up tissues, tissue make up organs, organs make up organ systems and finally organ systems make up organisms. Since complex multicellular organisms have a very high degree of organisation in their body, they cannot be reproduced from their cut body parts by the process of regeneration.
For example, a dog is a complex multicellular organism which cannot be regenerated from its cut body part say, a cut tail. This is because the cells present in the cut tail of a dog cannot produce dog’s organs like heart brain, lungs, stomach, intestines and limbs, etc, needed for the making of a complete dog.

Question 4:
Why is vegetative propagation practised for growing some types of plants ?

Answer 4:
Following are the advantages of practising vegetative propagation for growing some types of plants:
1.Crops like orange, banana, pineapple do not have viable seeds, so vegetative propagation can be used.
2.It is a rapid, cheap and easier method to grow crops.
3.It can be used in places where seed germination fails.
4.A good quality of variety can be preserved.

Question 5:
Why is DNA copying an essential part of the process of reproduction?

Answer 5:
DNA copying is essential part of the process of reproduction so that the characteristics of the parent organisms are transmitted to its offspring and at the same time some occasional variations are also produced in the offspring. The changes in the copy of DNA provide an organism the capability to survive in changing conditions.

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In-Text Questions (Page 140)

Question 1:
How is the process of pollination different from fertilisation ?

Answer 1:
Pollination is defined as the process of transfer of pollens from anther to stigma. The process takes place with the help of pollinators like air, water and some insects.
Fertilization is defined as the fusion of male and female gametes. It takes place in the ovule and leads to the formation of zygote.

Question 2:
What is the role of the seminal vesicles and the prostate gland?

Answer 2:
Lubrication of sperms and providing of a fluid medium for the easy transportation of sperms takes place with the help of secretions from the seminal vesicles and the prostate gland. These secretions also provide nutrients in the form of fructose, calcium and some enzymes.

Question 3:
What are the changes seen in girls at the time of puberty?

Answer 3:
The various changes occur in girls at puberty are :

1. Hair grow under armpits and pubic region.
2. Mammary glands (or breasts) develop and enlarge.
3. The hips broaden.
4. Extra fat is deposited in various parts of the body like hips and thighs.
5. Fallopian tube, uterus and vagina enlarge.
6. Ovaries start to release eggs.
7. Menstruation (monthly periods) starts.
8. Feelings and sexual drives associated with adulthood begin to develop.

Question 4:
How does the embryo get nourishment inside the mother’s body ?

Answer 4:
The lining of the uterus thickens after fertilization. The blood flow is good so as to nourish the growing embryo. Placenta is a special tissue which is embedded in the uterine wall and helps the embryo get the nourishment from the mother’s tissue. Placenta has villi on the embryo side and blood space on the mother’s side. This spacing provides a large area between the mother and the embryo and also for waste removal.

Question 5:
If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?

Answer 5:
Copper-T is a contraceptive method which prevents implantation of the zygote inside the uterus. It cannot prevent a women from sexually transmitted diseases. These diseases are transmitted by contact which cannot be prevented by copper-T.

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Exercise Questions (Page 141)

Question 1:
Asexual reproduction takes place through budding in
(a) amoeba
(b) yeast
(c) plasmodium
(d) leishmania

Answer 1:
(b) Yeast
Yeast is an example for asexual reproduction taking place through budding. A small protuberance is produced on the parent cell that grows in full size forming a bud. In the parent cell, the daughter nucleus splits and migrates to the daughter cell. By forming a constriction, the bud detaches from the mother’s body at the base. This process of budding continues to form a chain of bud cells. The mother cell is smaller than the daughter cell.

Question 2:
Which of the following is not a part of the female reproductive system in human beings ?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube

Answer 2:
(c) Vas deferens
Vas deferens is a part of male reproductive system. It is a long, muscular tube travelling from the epididymis into the pelvic cavity. It is behind the bladder. Its function is to transport the mature sperm to the urethra. It also carries urine to the outside of the body.

Question 3:
The anther contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains

Answer 3:
(d) Pollen grains.
Pollen grains are the microscopic particles that occurs in the pollen giving rise to male gametophyte of a seed plant.

Question 4:
What are the advantages of sexual reproduction over asexual reproduction?

Answer 4:
(i) In asexual reproduction, the offspring are almost identical to their parent because they have the same genes as their parent. So, much genetic variation is not possible in asexual reproduction. This is a disadvantage because it inhibits the further evolution of the organism.

(ii) In sexual reproduction the offspring, although similar to their parents, are not identical to them or to one another. This is because the offspring receive some genes from the mother and some from the father. Because of the mixing of genes of mother and father in various different combinations, all of the offspring have genetic variations. In this way, sexual reproduction leads to a greater variety in population. This means that a species (animal or plant) can adapt quickly to changes in its surroundings. This is because there are always likely to be some individuals which are more suited to the changes than others, and these individuals will survive and reproduce themselves.

Question 5:
What are the functions performed by the testis in human beings ?

Answer 5:
The functions of testes in humans are following :
(i) After the stage of adolescent, testes produce male gametes in the human males which are called sperms.
(ii) A hormone called testosterone is produced in testes. Testosterone controls the development of reproductive organs and secondary sexual characters.

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Question 6:
Why does menstruation occur ?

Answer 6:
Menstruation is the normal bleeding of the vaginal line which starts between puberty and lasts till menopause. During this period, the body prepares itself for pregnancy.
Every month an egg is released from one of the ovaries at the same time where the uterus prepares itself for fertilized egg. The inner lining of the uterus gets thickened and is supplied with sufficient amount of blood for the embryo. Since there is no interaction between the egg and the sperms, the fertilization of egg doesn’t takes place. So when the egg doesn’t get fertilized, the uterus lining breaks down slowly resulting in menstruation.

Question 7:
Draw a labelled diagram of the longitudinal section of a flower.

Answer 7:

Question 8:
What are the different methods of contraception?

Answer 8:
The different methods of contraception are as follow :
(i) Barrier method : In this method, condom, diaphragm and cervical caps are used. These prevent the entry of sperms in the female genital tract during sexual intercourse.
(ii) Chemical method : In this method a woman uses two kinds of pills (oral and vaginal pills). The oral pills are hormonal preparations which suppress the release of ovum in fallopian tube. These are called oral contraceptives. The vaginal pills/ creams are spermicidal. The chemicals in these spermicidals kill the sperms during their journey in the vaginal tract.
(iii) Intrauterine contraceptive devices : Intrauterine contraceptive devices such as copper-T are placed safely in the uterus by a skilled doctor. It prevents the sperms to reach the uterus.
(iv) Surgical method : In this method, a small part of vas deferens of male and fallopian tube of female is cut or tied by surgery. It is called vasectomy in males and tubectomy in females.

Question 9:
How are the modes for reproduction different in unicellular and multicellular organisms?

Answer 9:
The different modes of reproduction in unicellular organisms are fission, budding, etc. Here, the cell divides into two daughter cells and this process of cell division continues.
Whereas, in multicellular organisms there is a different organ system for reproduction. The different modes of reproduction in multicellular organisms are vegetative propagation, spore formation, etc.
In more complex organisms like humans and animals, the reproduction is through sexual reproduction.

Question 10:
How does reproduction help in providing stability to populations of species?

Answer 10:
The introduction of variations during reproduction provides stability to the populations of various species by preventing them from getting wiped out during adverse conditions. Reproduction also helps to generate copies of individuals which are suited to a particular environment.

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Question 11:
What could be the reasons for adopting contraceptive methods ?

Answer 11:
Following are the reasons for adopting contraceptive methods:

1.To control population
2.To avoid unplanned pregnancy
3.To avoid transfer of sexually transmitted diseases

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For More Content related to Class 10 –

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