NCERT solutions for class 8 Science Chapter 9 Reproduction In Animals

Solution for Exercise

Q.1Explain the importance of reproduction in organisms.


Open in new tab link

Answer :

Reproduction is a vital phenomenon on this planet earth which is essential for existence and continuity of life and species on it, generation after generation.

Q.2 Describe the process of fertilisation in human beings.


Open in new tab link

Answer :

Fertilization is defined as the process in which there is a fusion of male gamete and female gamete.
The male gametes or sperms are released from the male reproductive organ called the penis.
One of the sperms may fuse with the egg. The nuclei of the sperm and the egg fuse to form a single nucleus resulting in the formation of a fertilised egg called zygote.
In human being, the fertilisation takes place inside the female body, known as internal fertilisation.

Q.3 Choose the most appropriate answer.

(a) Internal fertilisation occurs

(i) in female body.
(ii) outside female body.
(iii) in male body.
(iv) outside male body.

(b) A tadpole develops into an adult frog by the process of

(i) fertilisation
(ii) metamorphosis
(iii) embedding
(iv) budding

(c) The number of nuclei present in a zygote is

(i) none
(ii) one
(iii) two
(iv) four


Open in new tab link

Answer :

a) (i) in female body.
b) (ii) metamorphosis
c) (iii) two

Q.4 Indicate whether the following statements are True (T) or False (F).
(a) Oviparous animals give birth to young ones. ( )
(b) Each sperm is a single cell. ( )
(c) External fertilisation takes place in frog. ( )
(d) A new human individual develops from a cell called gamete. ( )
(e) Egg laid after fertilisation is made up of a single cell. ( )
(f) Amoeba reproduces by budding. ( )
(g) Fertilisation is necessary even in asexual reproduction. ( )
(h) Binary fission is a method of asexual reproduction. ( )
(i) A zygote is formed as a result of fertilisation. ( )
(j) An embryo is made up of a single cell. ( )


Open in new tab link

Answer :

a) False
b) True
c) True
d) False
e) True
f) False
g) False
h) True
i) True
j) False

Q.5 Give two differences between a zygote and a foetus.


Open in new tab link

Answer :

zygote

(i) It is the earliest stage of development
(ii) It is formed by the fusion of male gamete or sperm and female gamete or ova (egg).

foetus

(i) it is the last stage of development
(ii) It is formed by the repeated division of the zygote.

Q.6 Define asexual reproduction. Describe two methods of asexual reproduction in animals.


Open in new tab link

Answer :

Asexual reproduction is a mode of reproduction that does not involve the fusion of the male and the female gamete. It requires only one parent, and the offsprings produced are exact copies of their parents.
(i) binary fission
It is a type of asexual reproduction in which a single cell divides into two halves. Organisms that reproduce through binary fission are bacteria and Amoeba. In Amoeba, the division of cells can take place in any plane. It involves the division of its nucleus into two nuclei, which is followed by the division of its body into two halves. Each half of the body receives a nucleus.

(ii) Budding
In budding, the organism develops a bulge called bud which further develops into an adult organism and separates itself from the parent body to lead an independent life. This type of reproduction is shown in Hydra. The following figure shows budding in Hydra

Q.7 In which female reproductive organ does the embryo get embedded?


Open in new tab link

Answer :

Uterus

Q.8 What is metamorphosis? Give examples.


Open in new tab link

Answer :

Metamorphosis is a biological process of transforming a larva into an adult. This involves relatively sudden and abrupt changes in the animal's structure. Frogs and insects are examples of organisms showing metamorphosis. The life cycle of a frog has three distinct stages:
EGG ? TADPOLE ? ADULT The tadpole emerging from the egg will have gills, tail, etc. They can swim easily in water. It undergoes abrupt changes and develops into a mature frog.

Q.9 Differentiate between internal fertilisation and external fertilisation.


Open in new tab link

Answer :

Internal Fertilisation

The fusion of male gamete or sperm and female gamete or ova occurs inside the body of a female partner, such as human beings, birds, and mammal.

external fertilisation

The fusion of male gamete and female gamete takes place outside the body of a female partner, such as in frog, fish and starfish.

Q.10 Complete the crossword puzzle using the hints given below.

Across

1. The process of the fusion of the gametes.
6. The type of fertilisation in a hen.
7. The term used for bulges observed on the sides of the body of Hydra.
8. Eggs are produced here.

Down

2. Sperms are produced in these male reproductive organs
3. Another term for the fertilised egg.
4. These animals lay eggs.
5. A type of fission in Amoeba


Open in new tab link

Answer :

Across

1) Fertilization
6) Internal
7) Buds
8) Ovary

Down

2) Testis
3) Zygote
4) Oviparous
5) Binary



Get it on Google Play