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NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

Exercises

Q1. Explain the importance of reproduction in organisms.
Ans: Reproduction is a biological process through which living organisms produce offspring similar to themselves. Living organisms reproduce to maintain their number and for the continuation of their species. Thus, reproduction ensures the continuation of similar kinds of individuals.NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

Regeneration Process


Q2. Describe the process of fertilization in human beings.
Ans:

  • Fertilization involves the fusion of the male and the female gamete. The male and the female gametes are released from the male and the female reproductive organs.NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals
  • Sperms or male gametes are released from the male reproductive organ, i.e., the penis.
  • These sperms then enter the female body through the vagina. Then, they travel through the fallopian tubes where they meet the eggs.
  • Hence, the process of fertilization takes place in the fallopian tubes.
  • During fertilization, the haploid nucleus of the sperm and that of the ovum fuse with each other to form the zygote.
  • This zygote divides to form an embryo which in turn develops into a foetus.


Q3. Choose the most appropriate answer.
(a) Internal fertilization occurs
(i) in the female body.
(ii) outside the female body.
(iii) in the male body.
(iv) outside the 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

Ans:
(a) (i) Internal fertilization occurs in the female body.
(b) (ii) A tadpole develops into an adult frog by the process of metamorphosis.NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

Metamorphosis in Frog

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


Q4. Indicate whether the following statements are True (T) or False (F).
(a) Oviparous animals give birth to young ones.

Ans: False

(b) Each sperm is a single cell.
Ans: True

(c) External fertilization takes place in frogs.
Ans: True

(d) A new human individual develops from a cell called a gamete.
Ans:  False

(e) Egg laid after fertilization is made up of a single cell.
Ans: True

(f) Amoeba reproduces by budding.
Ans: False

(g) Fertilization is necessary even in asexual reproduction.
Ans: False

(h) Binary fission is a method of asexual reproduction.
Ans: True

(i) A zygote is formed as a result of fertilization.
Ans: True

(j) An embryo is made up of a single cell.
Ans: False


Q5. Give two differences between a zygote and a foetus.
Ans: 

NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals


Q6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Ans: 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.
Two methods of asexual reproduction in animals are:
(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. NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals
  • 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

  • Budding involves the formation of a new individual from the bulges, known as buds formed on the parent body. This method of reproduction is common in Hydra. 
  • In Hydra, the cells divide rapidly at a specific site and develop as an outgrowth, called the bud.

NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

Budding in Hydra
  • These buds, while being attached to the parent plant, develop into smaller individuals. When these individuals become mature enough, they detach from the parent's body and become independent individuals.


Q7. In which female reproductive organ does the embryo get embedded?
Ans: The embryo gets embedded in the wall of the uterus. The embryo, while it is still attached to the uterus, gradually develops various body parts such as hands, legs, head, eyes, etc. The embryo is then called a foetus.


Q8. What is metamorphosis? Give examples.
Ans: Metamorphosis is a biological process of transforming a larva into an adult. This involves relatively sudden and abrupt changes in the animal's structure.
Example: Frogs and insects.
The life cycle of a frog has three distinct stages:
(i) Egg
(ii) Tadpole
(iii) Adult


NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

The Life Cycle of Frog

The life cycle of a frog:

  • The tadpole that emerges from the egg contains gills, a tail, and a small circular mouth. They can swim freely in the water. 
  • The tadpole grows and involves abrupt changes in its structure and develops into a mature frog. 
  • A tadpole's metamorphosis begins with the development of limbs, lung development, and finally, the absorption of the tail by the body.


Q9. Differentiate between internal fertilization and external fertilization.
Ans:
NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals
Q10. Complete the crossword puzzle using the hints given below.
Across-
1. The process of the fusion of the gametes.
6. The type of fertilization in the 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.

NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

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

NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

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FAQs on NCERT Solutions for Class 8 Science Chapter 6 - Reproduction in Animals

1. What is reproduction in animals?
Ans. Reproduction in animals is the biological process by which organisms produce offspring. It involves the transmission of genetic material from parent to offspring. Reproduction can be sexual or asexual, and the methods of reproduction vary significantly among different animal species.
2. What are the different modes of reproduction in animals?
Ans. The different modes of reproduction in animals are sexual and asexual reproduction. In sexual reproduction, two parents contribute genetic information to produce offspring. Asexual reproduction, on the other hand, involves the production of offspring without the involvement of gametes or fertilization. Some animals also exhibit alternate modes of reproduction, such as hermaphroditism, parthenogenesis, and cloning.
3. How do animals reproduce asexually?
Ans. Animals can reproduce asexually through various means. For example, some animals can reproduce by budding, where a new individual grows as an outgrowth from the parent organism. Other animals can reproduce through fragmentation, where a piece of the parent organism breaks off and grows into a new individual. Some animals can also reproduce through parthenogenesis, where an unfertilized egg develops into a new individual.
4. What are the advantages of sexual reproduction?
Ans. Sexual reproduction has several advantages over asexual reproduction. One of the primary advantages is genetic diversity, which allows for adaptation to changing environments and provides a greater likelihood of survival for the offspring. Sexual reproduction also allows for the repair of damaged DNA, as the offspring receive genetic material from two parents. Additionally, sexual reproduction can help to eliminate harmful mutations and maintain healthy populations.
5. How is reproduction in animals important for the survival of the species?
Ans. Reproduction is essential for the survival of animal species. It enables the production of offspring, which ensures the continuation of the species. Reproduction also allows for genetic diversity, which helps to ensure the survival of the species in changing environments and in the face of disease or other threats. Additionally, reproduction allows for the transfer of genetic information from one generation to the next, which helps to maintain healthy populations and prevent the accumulation of harmful mutations.
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