Chapter 9 . REPRODUCTION IN ANIMALS

Exercises

1. Explain the importance of reproduction in organisms.

Answer : Reproduction is of vital importance in organisms for the continuation and survival of the species. It allows for the production of offspring, ensuring the genetic diversity and adaptation to changing environments. Reproduction enables the transfer of genetic information, passing on traits and characteristics, and maintaining the overall biodiversity and evolutionary processes in the natural world.

2. Describe the process of fertilisation in human beings.

Answer : Fertilization in human beings involves the fusion of a sperm cell and an egg cell. During sexual intercourse, sperm are ejaculated into the vagina and travel through the cervix and into the fallopian tube. If a sperm successfully penetrates the egg, fertilization occurs, forming a zygote. The zygote then undergoes cell division and implants into the uterus, initiating pregnancy.

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.

Answer : (i) in female body.

(b) A tadpole develops into an adult frog by the process of
(i) fertilisation (ii) metamorphosis (iii) embedding (iv) budding

Answer :  (ii) metamorphosis.

(c) The number of nuclei present in a zygote is
(i) none (ii) one (iii) two (iv) four

Answer : (ii) one.

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) False (F)

(b) True (T)

(c) True (T)

(d) False (F)

(e) True (T)

(f) False (F)

(g) False (F)

(h) True (T)

(i) True (T)

(j) False (F)

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

Answer : Two differences between a zygote and a foetus.

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

Answer :  Asexual reproduction is a mode of reproduction in which offspring are produced from a single parent without the involvement or fusion of gametes (reproductive cells). In asexual reproduction, offspring are genetically identical or very similar to the parent, as there is no mixing of genetic material.

Two methods of asexual reproduction in animals are:

Budding: Budding is a form of asexual reproduction in which a new individual develops as an outgrowth or bud on the parent organism. The bud grows and eventually detaches from the parent, becoming an independent organism. Examples of animals that reproduce by budding include certain species of cnidarians (such as hydra) and some types of sponges.

Fragmentation/Regeneration: Fragmentation involves the breaking or splitting of the parent organism into two or more fragments, each of which can develop into a new individual. Regeneration refers to the ability of these fragments to grow and develop into complete organisms. Many invertebrates, such as flatworms (planarians), exhibit the ability to regenerate from fragments. For example, if a planarian is divided into multiple pieces, each fragment has the potential to regenerate missing body parts and develop into a fully functional organism.

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

Answer : The embryo gets embedded in the uterus, specifically in the lining of the uterus known as the endometrium.

8. What is metamorphosis? Give examples.

Answer : The transformation of the larva into an adult through drastic changes is called metamorphosis .

Frogs, butterflies, and dragonflies are examples of organisms that undergo metamorphosis, transforming from one form to another during their life cycle.

9. Differentiate between internal fertilisation and external fertilisation.

Answer : Internal fertilisation :

Fertilisation that takes place inside the female body is called internal fertilisation. This is observed in human beings and other animals such as hens, cows and dogs.

External fertilisation :

Fertilisation that takes place outside the female body is called external fertilisation. This is observed in frogs, fish, starfish, etc

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 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 in vitro fertilisation.
4. These animals lay eggs.
5. A type of fission in amoeba.

Answer :