Class 8 Science
Reproduction
NCERT Solution
Question 1: Explain the importance of reproduction in organisms.
Answer: Reproduction is very important for organisms because reproduction ensures that a particular species continues its existence on earth.
Question 2: Describe the the process of fertilization in human beings.
Answer: A single egg comes out of the ovary every month, and reaches the fallopian tube. Sperms reach the fallopian tube where a sperm fertilizes the egg. This results in formation of zygote.
Question 3: Internal fertilization occurs
- In female body
- Outside female body
- In male body
- Outside male body
Answer: (a) In female body
Question 4: A tadpole develops into an adult frog by the process of
- Fertilization
- Metamorphosis
- Embedding
- Budding
Answer: (b) Metamorphosis
Question 5: The number of nuclei present in a zygote is
- None
- One
- Two
- Four
Answer: (b) One
Question 6: Indicate whether the following statements are True (T) or False (F):
- Oviparous animals give birth to young ones.
- Each sperm is a single cell.
- External fertilization takes place in frog.
- A new human individual develops from a cell called gamete.
- Egg laid after fertilization is made up of a single cell.
- Amoeba reproduces by budding.
- Fertilization is necessary even in asexual reproduction.
- Binary fission is a method of asexual reproduction.
- A zygote is formed as a result of fertilization.
- An embryo is made up of a single cell.
Answer: (a) F, (b) T, (c) T, (d) F, (e) F, (f) F, (g) F, (h) T, (i) T, (j) F
Question 7: Give two differences between a zygote and a foetus.
Answer:
| Zygote | Foetus |
|---|
| Begins as a single cell. | Begins as multicellular structure. |
| Resembles a unicellular organism. | Resembles a human being. |
Question 8: Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Answer: When a single parent is involved in reproduction and gametes are not formed, it is called asexual reproduction. Two methods of asexual reproduction are as follows:
Budding: This method is seen in multicellular animals which are highly simple in structure. A small bud develops on the body. The bud develops and starts resembling its mother. After that, the bud gets detached from the mother’s body to begin life as a new individual. Examples: Hydra and sponges.
Binary Fission: This method is seen in unicellular animals, e.g. amoeba. The cell of amoeba divided into two daughter cells. Each daughter cell becomes a new individual.
Question 9: In which female reproductive organ does the embryo get embedded?
Answer: Uterus
Question 10: What is metamorphosis? Give examples.
Answer: In case of indirect development, transformation of young ones into adult is called metamorphosis. Larva of butterfly undergoes metamorphosis to become a butterfly. A tadpole undergoes metamorphosis to become a frog.
Question 11: Differentiate between internal fertilization and external fertilization.
Answer:
| External Fertilization | Internal Fertilization |
|---|
| Takes place outside the body of animal. | Takes place inside the body of animal. |
| A large number of eggs need to be laid. | No need to lay large number of eggs. |
| Is seen in most of the aquatic animals. | Is seen in reptiles, birds, mammals and in some fish. |