MG SCHOOL SCIENCE: Cls 10 Chp 8 solsn

Class 10 Science

Chapter 8 How Do Organisms Reproduce?

Intext Question and Answer

Page Number: 128

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

Ans:

DNA copying has following importance in reproduction:

It maintains the characteristics of species.
It maintains the continuity of life.
From this, the characteristics and features of organisms are transformed to their progeny.
It produces variations in organisms which is the basis of evolution of new species.

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

Ans:

The various populations of organisms interact with many types of ecological niches. This is important for them to survive in given conditions. In case of any damage caused to the ecological conditions of the population, the population gets adversely affected. The organisms which are able to survive, may reproduce to develop population which is adapted or suited to the varied conditions. Hence variation is beneficial to species, but not to the individuals.

Page Number: 133

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

Ans:

★ When a single cell divides into two equal halves, it is known as binary fission. Bacteria and amoeba are 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 examples of multiple fission.

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

Ans: 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.

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

Ans: 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.

4. Why is vegetative propagation practised for growing some types of plants?
Ans: Vegetative propagation is practiced for growing such plants which usually do not produce seeds or produce non-viable seeds.

5. Why is DNA copying an essential part of the process of reproduction?
Ans:
★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.

Page Number: 140

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

Ans:

Pollination	Fertilisation
1. The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination.	1. Fertilisation occurs when the male gamete present in pollen grain joins with the female gamete (or egg) present in ovule.
2. It takes place by various pollinating agents.	2. It takes place by natural or artificial means.

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

They add their secretion to make the sperm transport easier and provide nutrition.

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

Ans : The various changes occur in girls at puberty are :

★ Hair grow under armpits and pubic region.

★ Mammary glands (or breasts) develop and enlarge.

★ The hips broaden.

★ Extra fat is deposited in various parts of the body like hips and thighs.

★ Fallopian tube, uterus and vagina enlarge.

★ Ovaries start to release eggs. g. Menstruation (monthly periods) starts.

★ Feelings and sexual drives associated with adulthood begin to develop.

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

★The embryo gets nourishment inside the mother body through a special tissue called placenta.

★It provides a large surface area for the transfer of glucose, oxygen and other substances from the mother to the embryo.

5. A woman is using a copper-T. Will it help in protecting her from sexually transmitted diseases ?

Ans:

It cannot prevent a women from sexually transmitted diseases. These diseases are transmitted by contact which cannot be prevented by copper-T.

Exercise Questions

1. Asexual reproduction takes place through budding in

(a) amoeba (b) yeast

Ans: (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
Ans: (c) Vas deferens

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

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

Ans:

Following are the advantages of sexual reproduction:

The offspring has the characters of both the parents.
The survival of the species is ensured as there are more variations.
The offspring can easily adapt to environmental changes.
It also improves the health of humans.

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

Ans:

They are responsible for producing the male sex hormone, testosterone. They are responsible for producing sperms

6. Why does menstruation occur ? (Sep 2020)

Ans. :

★ The uterus prepares itself every month to receive a fertilized egg and thus its lining becomes thick and spongy.

★ If the egg is not fertilized, the lining slowly breaks and comes out through the vagina as blood and mucous.

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

8. What are the different methods of contraception?

Ans:

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.

9. How are the modes for reproduction different in unicellular and multicellular organisms?
Ans:
Reproduction mode in unicellular organisms Reproduction mode in multicellular organisms
(i) A sexual reproduction takes place in unicellular organisms. (i) Sexual reproduction takes place in multicellular organisms.
(ii) Only one organism is required in this method. (ii) A male and a female both are required in this method.
(iii) No special cells are present for reproduction. (iii) Special cells are present for reproduction.
(iv) No special organs are present for reproduction. (iv) Special organs are present for reproduction located at the fixed position in the body.

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

Ans:

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.

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

Ans:

The reasons for adopting contraceptive devices are as follow:

To control the birth rate and prevent the increase in population.
To reduce the adverse effects on mother’s body due to frequent pregnancy.
To provide safety from sexually transmitted diseases.