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

NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce? are also updated on a regular basis, ensuring that students have access to the latest information. It is one of the best ways to prepare for your exams and get good grades. The Solutions provide clear and concise explanations to all the questions present in the NCERT textbooks.

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

In Text Questions

1. What is the importance of DNA copying in reproduction?

Solution

If organisms are similar in body design, their blueprints should be similar as well. Thus, when DNA copies are made during reproduction, it copies the blueprints of body design.

2. Why is variation beneficial to the species but not necessarily for the individuals?

Solution

Cells that reproduce will generate DNA copies that are similar to the original, but not exactly the same. Hence, the cells will be subtly different from each other. This inbuilt tendency for variation to happen during reproduction is the main cause of the formation of new species. In this regard, variation is beneficial to the species but not necessarily to the individual.

1. How does binary fission differ from multiple fission?

Solution

Binary fission	Multiple fission
When a parent cell produces two daughter cells it is called binary fission.	When a parent cell produces more than two daughter cells it is called multiple fission.
The parent nucleus divides into two and goes to two daughter cells.	The parent nucleus divides into many daughter nuclei each surrounded by cytoplasm.
It is usually during favourable conditions.	It is usually during unfavourable condition in other protozoans.
No protective covering is formed.	A protective covering cyst is formed.

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

Solution

(i) Spores are produced in large numbers. So the population will increase soon on their growth.
(ii) Spores have a protective coat that helps them to resist unfavourable environmental conditions that are harmful to plant.
(iii) Spores are carried to long distances by wind. This helps in their distribution and growth.

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

Solution

More complex organisms have very high degree of organization within their body, such as specialized cells that form tissues, tissues that form organs, organ systems that form organisms. Since they have a relatively simple body organization consisting of only a few specialized cells, they cannot be reproduced from their cut body parts by regeneration. Hydra and Planaria, for example, can reproduce through regeneration.

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

Solution

Vegetative propagation is a means of propagating such plants which do not produce viable seeds. It is a rapid method of producing young ones. It helps in retaining useful characters from generation to generation.

5. Why is DNA copying essential part of the process of reproduction?

Solution

DNA copying is an essential part of the process of reproduction because it ensures that same blueprint of the body design is maintained.

1. How is the process of pollination different from fertilisation?

Solution

Pollination is the process in which pollen grains are transferred from anther to the stigma of a flower. Fertilisation is the process in which fusion of male gamete with female gamete takes place to form zygote.

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

Solution

Seminal vesicles. It produces a nutritive secretion needed for the sperms.
Prostate glands. It produces a fluid medium necessary for transport of the sperms.

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

Solution

Changes at puberty occur under the influence of FSH (Follicle stimulating hormone) and estrogen hormone. The following changes are seen in girls at the time of puberty:

(i) Growth of breast and external genitalia.
(ii) Darkening of nipple skin.
(iii) Broadening of pelvis.
(iv) Growth of pubic and axillary hair.
(v) Increase in subcutaneous fat.
(vi) Initiation of menstruation and ovulation.

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

Solution

Embryo gets nourishment through placenta inside the mother’s body. Placenta is a disc-like special tissue embedded in the wall of uterus. It contains villi on the embryo side of tissue. On the mother side are blood spaces which surround villi. Placenta brings the foetal and maternal blood close enough to permit exchange of materials between the two.

5. If a woman is using a copper-T, will it help her in protecting sexually transmitted diseases?

Solution

Copper-T can prevent unwanted pregnancy but cannot protect women from acquiring sexually transmitted diseases.

Exercises

1. Asexual reproduction takes place through budding in
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania

Solution

(b) Yeast

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

Solution

(c) Vas deferens

3. The anther contains
(a) Sepals
(b) Ovules
(c) Carpel
(d) Pollen grains

Solution

(d) Pollen grains

4. What are the advantages of sexual reproduction over asexual reproduction?

Solution

(i) Sexual reproduction takes place in presence of male and female individuals/parents/gametes.
(ii) The offspring produced are genetically variable. Such organisms are successful in environment. This promotes diversity and evolution. It plays important role in origin of new species.
(iii) It provides chances of many variations.

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

Solution

(i) Testis produce haploid and motile male gametes called sperms.
(ii) To produce testosterone (male sex hormone).

6. Why does menstruation occur?

Solution

Menstruation occurs to remove the unfertilised egg, the thick and spongy lining formed on the utrine wall. It marks the end of one cycle and to restart the next phase of egg maturation and provide a second chance for fertilisation of egg.

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

Solution

8. What are the different methods of contraception?

Solution

(i) Chemical method: In this method specific drugs are used by females like oral pills. Oral pills mainly contain hormones and are called oral contraceptives.
(ii) Barrier method: In this method physical devices like condom, cervical caps and diaphragm are used to prevent sperms to reach up to the ovum.
(iii) Intrauterine Contraceptive Devices (IUCD): IUCD like Copper-T is placed safely in the uterus by a skilled doctor. IUCDs prevent implantation of the fertilized ovum inside the uterus.
(iv) Surgery: Both men and women can use this method. A small section of vas deferens is surgically removed in males and the fallopian tube in females is ligated. A vasectomy prevents sperm from being released from the testes in males, whereas a tubectomy is performed in females.

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

Solution

Modes of reproduction in unicellular organisms	Modes of reproduction in multicellular organisms
The mode of reproduction is simple and involves the division of the parent cell.	The mode of reproduction is complex and involves the production of specialised cells.
Fertilisation process is absent.	Fertilisation process is present.
No specialised system are involved.	Specialised system are involved.
Simple modes of reproduction takes place.	Complex mode of reproduction takes place.
No variation in the individuals take place.	Variation in the individuals produced take place.
Only one individual is involved.	Two individuals of opposite sex are involved.

10. How does reproduction help in providing stability to population of species?

Solution

By reproducing, more organisms are produced with the same characteristics as their parents. It is possible, however, for some species of living organism to die out and disappear from the earth if they are unable to reproduce for some reason. As a consequence, reproduction is the only method for stabilizing a species’ population.

11. What could be the reasons for adopting contraceptive methods?

Solution

(i) These methods prevent pregnancy in women.
(ii) These methods also prevent transmission of sexually transmitted diseases.
(iii) To avoid unwanted pregnancies.