Reproduction in Animals - Class 8 : NCERT Exercise Questions



Q.1 Explain the importance of reproduction in organisms.
Sol. The importance of reproduction in organisms is:
(i) Reproduction is essential for the continuation of a species.
(ii) Reproduction ensures the continuation of similar kinds of individuals, generation after generation.

Q.2 Describe the process of fertilization in human beings.
Sol. The mode of reproduction in human beings is sexual reproduction. Female gametes produce ova while the male reproductive organs produce sperms. The sperms are ejected inside female bodies where they fuse with ovum and forms zygote, this process is known as internal fertilization. The zygote, then, begins to develop into an embryo which attaches to the female uterus wall. The embryo further multiples into many cells and finally develops into a small baby called foetus.

Q.3 Choose the most appropriate answer:
(a) Internal fertilization 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) fertilization.                  (ii) metamorphosis.
(iii) embedding.                 (iv) budding.
(c) The number of nuclei present in a zygote is
(i) none.                              (ii) one.
(iii) two.                             (iv) four.
Sol. (a) (i) in female body.
(b) (ii) metamorphosis.
(c) (ii) one.

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 fertilization takes place in frog.                                                   ( )
(d) A new human individual develops from a cell called gamete.                  ( )
(e) Egg laid after fertilization is made up of a single cell.                              ( )
(f) Amoeba reproduces by budding.                                                               ( )
(g) Fertilization is necessary even in asexual reproduction.                           ( )
(h) Binary fission is a method of asexual reproduction.                                 ( )
(i) A zygote is formed as a result of fertilization.                                           ( )
(j) An embryo is made up of a single cell.                                                      ( )
Sol. (a) Oviparous animals give birth to young ones.                                      (False)
(b) Each sperm is a single cell.                                                                        (True)
(c) External fertilization takes place in frog.                                                   (True)
(d) A new human individual develops from a cell called gamete.                  (False)
(e) Egg laid after fertilization is made up of a single cell.                              (True)
(f) Amoeba reproduces by budding.                                                               (False)
(g) Fertilization is necessary even in asexual reproduction.                           (False)
(h) Binary fission is a method of asexual reproduction.                                 (True)
(i) A zygote is formed as a result of fertilization.                                           (True)
(j) An embryo is made up of a single cell.                                                      (False)

Q.5 Give two difference between a zygote and a foetus.
Sol. The differences between a zygote and a foetus are:

Zygote

Foetus

It is single cellular.

It is multi-cellular.

It does not have well defined body parts.

It has well defined limbs and other body parts.

Q.6 Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Sol. Asexual reproduction is a mode of reproduction in which only one parent is involved to reproduce offspring. In this type of reproduction, the offsprings produced are exact copies of their parents. Asexual reproduction is generally observed in very small sized organisms. Examples of asexual reproduction are Binary fission, Budding, Fragmentation etc.
Budding: In this mode of asexual reproduction, a part of the organism starts bulging out and slowly it grows and develops into a separate individual. Example: Hydra, yeast, etc.
Binary Fission: In this mode of asexual reproduction, a single cell divides into two halves. Example: Bacteria, amoeba, etc.

Q.7 In which female reproductive organ does the embryo get embedded?
Sol. The female reproductive organ in which the embryo gets embedded is in the walls of the uterus.

Q.8 What is metamorphosis? Give examples.
Sol. The transformation of the larva into an adult through drastic changes is called metamorphosis. It is a biological process which involves sudden and abrupt changes in the body structure of the animal by cell growth and differentiation. It is generally observed in amphibians and insects. Example: Frogs, butterflies, etc.

Q.9 Differentiate between internal fertilization and external fertilization.
Sol. The differences between internal and external fertilization are:

Internal Fertilization

External Fertilization

In this type of fertilization, the fusion of male and female gametes takes place inside the body.

In this type of fertilization, the fusion of male and female gametes takes place outside the body.

In this type of fertilization, there are high chances of survival of offspring.

In this type of fertilization, there are low chances of survival of offspring.

In this type of fertilization, less numbers of eggs are produced.

In this type of fertilization, large numbers of eggs are produced.

Example: Cows, Hens, Human beings, etc.

Example: Fish, Frog, etc.

Q.10 Complete the cross-word puzzle using the hints given below
Across:
1. The process of the fusion of the gametes.
6. The type of fertilization 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 the fertilized egg.
4. These animals lay eggs.
5. A type of fission in amoeba.Sol. Across:
1. Fertilization
6. Internal
7. Buds
8. Ovary
Down:
2. Testis
3. Zygote
4. Oviparous
5. Binary



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