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:

ZygoteFoetus
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 FertilizationInternal 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.