NCERT Solutions for Class 8 Science
Chapter 9 Reproduction in Animals
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NCERT Solutions for Class 8 Science Chapter 9 Reproduction in Animals
1. Explain the importance of reproduction in organisms.
Answer: A process in which an organism produces an offspring similar to them is called as reproduction. Reproduction is important in organisms for continuation in species.
2. Describe the process of fertilisation in human beings.
Answer: Mode of reproduction in human beings is sexual reproduction. Male reproductive organs produce male gametes called sperms. Female reproductive organs produce female gametes called ova. Sperms are ejected inside the female body and fusion of sperms and ova takes place forming zygote. This process is called internal fertilisation. Zygote so formed is single celled which further divides again and again forming many cells and ultimately forming a baby called foetus.
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: (iii) two (when male and female gametes are fused).
4. Indicate whether the following statements are True (T) or False (F).
(a) Oviparous animals give birth to young ones.
Answer: False (F). [ Viviparous animals gives birth to young ones ]
(b) Each sperm is a single cell.
Answer: True (T)
(c) External fertilisation takes place in frog.
Answer: True (T)
(d) A new human individual develops from a cell called gamete.
Answer: False (F). [ Human individual develops from cell called zygote ]
(e) Egg laid after fertilisation is made up of a single cell.
Answer: True (T)
(f) Amoeba reproduces by budding.
Answer: False (F). [ Amoeba reproduces by binary fission ]
(g) Fertilisation is necessary even in asexual reproduction.
Answer: False (F). [ Fertilization is necessary only in sexual reproduction ]
(h) Binary fission is a method of asexual reproduction.
Answer: True (T)
(i) A zygote is formed as a result of fertilisation.
Answer: True (T)
(j) An embryo is made up of a single cell.
Answer: False (F). [ Embryo is multicellular ]
5. Give two differences between a zygote and a foetus.
Answer:
| Zygote | Foetus |
|---|---|
| It is single celled | It is multi celled |
| Body parts are not defined | Body parts are defined |
| Formed due to fertilization of male and female gametes | Formed when zygote divides again and again to form multicellular body structures |
| Zygote divides to form an embryo | Embryo is further developed to form foetus |
6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Answer: Reproduction in which offspring is present from single parent is called asexual reproduction.
- Budding – Part of organism bulges out which develops into new organism is called budding. Hydra undergoes asexual reproduction by this mode.
- Binary fission – In binary fission, a single cell divides into two halves. Amoeba reproduces by this method.
7. In which female reproductive organ does the embryo get embedded?
Answer: Embryo gets embedded in the walls of uterus. Once embryo gets attached to walls of uterus, it further develops into different body parts of foetus.
8. What is metamorphosis? Give examples.
Answer: A biological process in which larvae transforms into adult is called metamorphosis. This process is generally found in frogs, butterflies, etc.
9. Differentiate between internal fertilisation and external fertilisation.
Answer:
| Internal Fertilization | External Fertilization |
|---|---|
| When male and female gametes fuse inside the female body is called internal fertilization. | When male and female gametes fuse outside the female body is called external fertilization. |
| Less number of eggs are produced as chances of survival of offspring is high. | Large number of eggs are produced as chances of survival of offspring is low. |
| Cows, humans, etc show internal fertilization. | Frogs, starfish, etc show external fertilization. |
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:
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Chapter 9 – Reproduction in Animals