Question 1. Explain the importance of reproduction in organisms.
Solution 1. The following are the importance of reproduction in organisms:
- In this process living organisms give birth to their offspring.
- It helps in maintaining and increasing the population of the species.
- Reproduction is important for the survival of all living things.
Question 2. Describe the process of fertilization in human beings.
Solution 2.
- The process in which there is a fusion of the male gamete and female gamete is known as fertilization.
- The male reproductive organ called the penis releases the male gametes or sperms.
- The released sperms enter the female body through the vagina.
- From the vagina, sperms meet the eggs while travelling through the fallopian tubes.
- In the fallopian tube, the process of fertilization takes place.
- The male and female gametes fuse together to form a zygote.
- The zygote further divides rapidly to form a group of cells called a morula. After approximately five days morula becomes the embryo.
- The foetus is present for about eight weeks after fertilization.
Question 3. Choose the most appropriate answer.
(a) Internal fertilisation 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) 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
Solution 3.
a) Internal fertilisation occurs
Ans. (i) in the female body.
b) A tadpole develops into an adult frog by the process of
Ans. (ii) metamorphosis
c) The number of nuclei present in a zygote is
Ans. (iii) two
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. ( )
Solution 4.
a) Oviparous animals give birth to young ones. False
b) Each sperm is a single cell. True
c) External fertilisation takes place in frogs. True
d) A new human individual develops from a cell called a gamete. False
e) Egg laid after fertilisation is made up of a single cell. True
f) Amoeba reproduces by budding. False
g) Fertilisation 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 fertilisation. True
j) An embryo is made up of a single cell. False
Question 5. Give two differences between a zygote and a foetus.
Solution 5.
| Zygote | Foetus |
| · Zygote is the earliest stage of development. | · Foetus is the last developmental stage of an organism. |
| · Zygote is formed by the fusion of male and female gametes. | · Foetus is formed after the repeated division of zygote. |
Question 6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Solution 6. In sexual reproduction only, a single parent is involved which means the offspring arises from a single organism without the fusion of male and female gametes.
Binary fission in amoeba
- Binary fission is a kind of asexual reproduction in which one cell is divided into two halves that is why it is known as binary fission.
- Amoeba is a unicellular organism that has a cell membrane, cell wall and cytoplasm.
- Karyokinesis is the process in which the nucleus of the amoeba first divides to form two daughter nuclei.
- Finally, the division of the body into two halves having a nucleus respectively takes place.
Budding in hydra
- Budding is the process in which the organisms such as hydra, use regenerative cells for reproduction.
- Buds develop as a small outgrowth on the parent’s body.
- buds receive the characteristics of the parent organism as it grows.
- Once it is developed, it gets detached and develops as an individual.
- In some rare cases, interconnected buds are formed because the buds don’t get detached.
- There are some other methods also like fragmentation, multiple fission etc.
Question 7. In which female reproductive organ does the embryo get embedded?
Solution 7. The embryo gets embedded to the uterus in the female reproductive organ. There occurs the formation of body parts like legs, hands, eyes etc. once it gets attached.
Question 8. What is metamorphosis? Give examples.
Solution 8.
- The biological process in which an animal’s body structure abruptly changes through cell growth and differentiation is known as metamorphosis.
- Examples are frog and insects.
The life cycle of a frog:
The tadpole emerges from the egg having gills, a tail, etc. they are able to swim in the water. After abrupt changes, the tadpole develops into a mature frog.
Question 9. Differentiate between internal fertilisation and external fertilisation.
Solution 9.
| Internal fertilization | External fertilization |
| Internal fertilization occurs inside the body. | External fertilization occurs outside the body. |
| chances of survival of the offspring are high. | chances of survival of the offspring are low |
| Examples are cows, humans, dogs, monkeys, etc.
|
Examples are fish, frogs, organisms etc.
|