NCERT Solutions Class 8 Science - Questions and Answers - PDF

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Chapter 9 – Structure and Functions.

Exercises

Question 1:

Explain the importance of reproduction in organisms.
Answer 1:
  • Reproduction is essential for the continuation of a species.
  • It ensures the continuation of similar kinds of individuals, generation after generation.

Question 2:

Describe the process of fertilization in human beings.
Answer 2:
There is sexual reproduction in human beings. Male reproductive organs produce sperms (male gametes) while the female gametes produce ova (female gametes). The sperms are ejected inside female bodies where they fuse with ovum and forms zygote (called internal fertilization). The zygote begins to develop into an embryo which attaches to the female uterus wall. The embryo further multiples into many cells and develops further into a small baby called foetus.

Question 3:

Choose the most appropriate answer:
  1. Internal fertilization occurs
    1. in female body.
    2. outside female body.
    3. in male body.
    4. outside male body.
  2. A tadpole develops into an adult frog by the process of
    1. fertilization.
    2. metamorphosis.
    3. embedding.
    4. budding.
  3. The number of nuclei present in a zygote is
    1. none.
    2. one.
    3. two.
    4. four.
Answer 3:
  1. Internal fertilization occurs
    (i) in female body.
  2. A tadpole develops into an adult frog by the process of
    (ii) metamorphosis.
  3. The number of nuclei present in a zygote is
    (ii) one.

Question 4:

Indicate whether the following statements are True (T) or False (F):

( )
( )
( )
( )
( )
( )
( )
( )
( )
( )

Answer 4:

(False)
(True)
(True)
(False)
(True)
(False)
(False)
(True)
(True)
(False)

Question 5:

Give two difference between a zygote and a foetus.
Answer 5:
  • Zygote is single cellular whereas foetus is a multicellular.
  • Well defined body parts are absent in zygote whereas in foetus body parts can be identified.

Question 6:

Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Answer 6:
Asexual reproduction is a mode of reproduction in which only one parent is involved to reproduce offspring. In asexual reproduction, the offsprings produced are exact copies of their parents.
It is generally observed in very small sized organisms. Binary fission, Budding, Fragmentation etc. are the examples of asexual reproduction.
  • Budding: In this mode, a part of the organism starts bulging out. Slowly it grows and develops into a separate individual. Examples: Hydra, yeast.
  • 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.

Question 7:

In which female reproductive organ does the embryo get embedded?
Answer 7:
In walls of the uterus.

Question 8:

What is metamorphosis? Give examples.
Answer 8:
The transformation of the larva into an adult through drastic changes is called metamorphosis. Metamorphosis 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.
Examples: frogs and butterflies.

Question 9:

Differentiate between internal fertilization and external fertilization.
Answer 9:
S.No. Internal Fertilization External Fertilization
1. Fusion of male and female gametes take place inside the body. Fusion of male and female gametes take place outside the body.
2. Less numbers of eggs are produced. Large numbers of eggs are produced
3. Examples: Cow, Dog, Human etc. Examples: Frog, Fishes etc.

Question 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.

Answer 10:
Across
1. Fertilization
6. Internal
7. Buds
8. Ovary
Down
2. Testis
3. Zygote
4. Oviparous
5. Binary

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