NCERT Solutions Class 8 Science Reproduction in Animals

NCERT Solutions for Class 8 Science for chapter 9 Reproduction in Animals

Exercises

Question-1 Explain the importance of reproduction in organisms.

Answer: Importance of reproduction in organisms is:

1. Reproduction ensures the continuity of a species.
2. It also maintains the number of individuals in a populatio
3. It is also responsible for variations in organisms in a population that help them to survive in the environment.

Question-2 Describe the process of fertilisation in human beings.

Answer: Fusion of a sperm and an ovum is called fertilisation. In human beings, the process of fertilisation takes place in the oviducts. The sperms produced by testes in male’s body are transferred into the female body. In female’s body, one matured ovum is released into the oviduct by one of the ovaries every month. In the oviduct, the sperm comes in contact with the ovum and fuses with it. During the process of fusion, the nuclei of the sperm and the ovum fuse to form one single nucleus this results in the formation of zygote.

Question-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.

Answer:

a) i. in female body
b) ii. metamorphosis
c) ii. one


Question-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.

Answer:
a) Oviparous animals give birth to young ones. (F)

b)Each sperm is a single cell. (T)

c) External fertilisation takes place in frog. (T)

d)A new human individual develops from a cell called gamete. (F)

e) Egg laid after fertilisation is made up of a single cell. (T)

f) Amoeba reproduces by budding. (F)

g)Fertilisation is necessary even in asexual reproduction. (F)

h)Binary fission is a method of asexual reproduction. (T)

i) A zygote is formed as a result of fertilisatio (T)

j) An embryo is made up of a single cell. (F)


Question-5 Give two differences between a zygote and a foetus.

Answer: Difference between Zygote and Foetus

Zygote

Foetus

It is unicellular; hence, no well-defined body parts.

It is multicellular and has well-defined body parts.

It forms due to the fertilisation of sperm and ovum.

It forms after the process of fertilisation in which zygote multiplies and grows into a multicellular body.


Question-6 Define asexual reproduction. Describe two methods of asexual reproduction in animals.

Answer: Asexual reproduction is a type of reproduction in which only one parent is involved and the offspring is genetically identical to the parent cell.

Two methods of asexual reproduction are budding and binary fission.

Budding: In this type of asexual reproduction, an outgrowth appears on the parent’s body. This outgrowth is termed as bud. The bud gradually grows into a small individual and then detaches itself from the parent’s body. It continues to grow and live as a new individual in the environment. Eg; Hydra.

Binary fission: In this type of asexual reproduction, the nucleus of the parent’s body divides into two nuclei. After that the body divides into two and each body part receives a nucleus. Eg; Amoeba.


Question-7 In which female reproductive organ does the embryo get embedded?

Answer: The embryo gets embedded in the walls of uterus. In the uterus, the embryo grows and develops all the body parts.


Question-8 What is metamorphosis? Give examples.

Answer: Metamorphosis is a biological process of transformation of an immature form such as larva into an adult through drastic changes. It is observed in frogs (transformation of tadpole into adult frog) and in insects (transformation of larva into moths or butterflies).


Question-9 Differentiate between internal fertlisation and external fertlisation.

Answer:

Characters

Internal Fertilisation

External Fertilisation

Site of fertilisation

Inside female body

Outside female body

Number of eggs/offspring produced

Less

Large

Chances of survival of eggs/offspring

High

Low

Example

Mostly mammals

Generally fish, frog


Question-10 Complete the cross-word puzzle using the hints given below:

Across

1.The process of fusion of gametes
6. Type of fertilisation in 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 fertilised egg
4. These animals lay eggs.
5. A type of fission in Amoeba.

Answer:

Across
1. Fertilization
6. Internal
7. Buds
8. Ovary

Down
2. Testis
3. Zygote
4. Oviparous
5. Binary

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