NCERT Solutions for Class 8th Science Chapter 4 Reproduction in Animals based on the latest syllabus of CBSE and JKBOSE NCERT Books
Reproduction in Animals
Exercises
1. Explain the importance of reproduction in organisms.
Answer: Reproduction is essential for the survival of species. It ensures the continuation of life by producing new individuals, maintaining the population, and enabling genetic variation and evolution.
2. Describe the process of fertilization in human beings.
Answer: Fertilization in humans occurs when a sperm cell from the male merges with an egg cell from the female. This process typically takes place in the fallopian tube. The sperm penetrates the egg’s outer layer, and their nuclei combine to form a zygote, which then develops into an embryo.
3. Choose the most appropriate answer:
(a) Internal fertilization occurs
- (i) in female body. ✔️
- (ii) outside female body.
- (iii) in male body.
- (iv) outside 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.
4. Indicate whether the following statements are True (T) or False (F):
(a) Oviparous animals give birth to young ones. ( False )
(b) Each sperm is a single cell. ( True )
(c) External fertilization takes place in frog. ( True )
(d) A new human individual develops from a cell called gamete. ( False )
(e) Egg laid after fertilization is made up of a single cell. ( True )
(f) Amoeba reproduces by budding. ( False )
(g) Fertilization 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 fertilization. ( True )
(j) An embryo is made up of a single cell. ( False )
5. Give two differences between a zygote and a foetus.
Answer:
- Zygote: A single cell formed after fertilization, which undergoes cell division.
- Foetus: A developing organism after the embryonic stage, where the basic structure and organs are formed.
6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Answer: Asexual reproduction is a mode of reproduction where a single organism produces offspring without the involvement of gametes. Two methods include:
- Binary Fission: An organism splits into two equal parts, each becoming a new individual. Example: Amoeba.
- Budding: A new organism grows out of the body of the parent organism. Example: Hydra.
7. In which female reproductive organ does the embryo get embedded?
Answer: The embryo gets embedded in the uterus of the female reproductive system.
8. What is metamorphosis? Give examples.
Answer: Metamorphosis is a biological process in which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal’s body structure. Examples include the transformation of a tadpole into a frog and a caterpillar into a butterfly.
9. Differentiate between internal fertilization and external fertilization.
Answer:
- Internal Fertilization: Occurs inside the female body. Examples: Humans, mammals.
- External Fertilization: Occurs outside the female body in the external environment. Examples: Fish, amphibians.
10. Complete the cross-word puzzle using the hints given below:
Across:
- The process of the fusion of the gametes. ( Fertilization )
- The type of fertilization in hen. ( Internal )
- The term used for bulges observed on the sides of the body of Hydra. ( Buds )
- Eggs are produced here. ( Ovary )
Down:
- Sperms are produced in these male reproductive organs. ( Testes )
- Another term for the fertilized egg. ( Zygote )
- These animals lay eggs. ( Oviparous )
- A type of fission in amoeba. ( Binary )
Extended Learning — Activities and Projects
- Visit a poultry farm: Talk to the manager of the farm and try to find out the answers to the following:
(a) What are layers and broilers in a poultry farm?
- Layers: Hens that are raised for laying eggs.
- Broilers: Chickens that are raised for meat.
(b) Do hens lay unfertilized eggs?
- Answer: Yes, hens can lay unfertilized eggs.
(c) How can you obtain fertilized and unfertilized eggs?
- Answer: Fertilized eggs are obtained by allowing hens to mate with roosters. Unfertilized eggs are laid by hens without mating.
(d) Are the eggs that we get in the stores fertilized or unfertilized?
- Answer: Most of the eggs available in stores are unfertilized.
(e) Can you consume fertilized eggs?
- Answer: Yes, fertilized eggs are also safe for consumption.
(f) Is there any difference in the nutritional value of the fertilized and unfertilized eggs?
- Answer: There is no significant difference in the nutritional value between fertilized and unfertilized eggs.
- Observe live hydra yourself and learn how they reproduce by doing the following activity:
- Collect water weeds from ponds or ditches and put them in a glass jar with pond water.
- After a day or so, observe hydra clinging to the sides of the jar.
- Using a hand lens or a binocular or dissection microscope, observe the changes that are taking place in their body and note down your observations.
