NCERT Class VIII Science Solutions: Chapter 9-Reproduction in Animals Part 3

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SHORT ANSWER QUESTIONS

Question 16:

Fill up the blanks with the terms given below:

Body, asexual, binary, single, nucleus Amoeba is a ___________ celled organism. It reproduces by ___________ reproduction. The process of reproduction begins by the division of its ___________ into two. This is followed by the division of its ___________ into two. This type of reproduction is called ___________ fission.

Answer:

Body, asexual, binary, single, nucleus Amoeba is a single celled organism. It reproduces by asexual reproduction. The process of reproduction begins by the division of its nucleus into two. This is followed by the division of its body into two. This type of reproduction is called binary fission.

Question 17:

The term metamorphosis is not used while describing human development. Why?

Answer:

In human beings, body parts of an adult are present from the time of birth itself. Whereas, in metamorphosis, the parts of the adult are different from those at the time of birth.

Image of metamorphosis

Image of Metamorphosis

Image of metamorphosis

Question 18:

Mother gives birth to a baby but the baby has characters of both parents. How is this possible?

Answer:

Although mother gives birth to a child, fertilisation involves two gametes, one from the mother and the other from father. The zygote therefore has both father and mother’s contribution. Since the zygote develops into the baby it has characters of both parents.

Question 19:

How is reproduction in hydra different from that in amoeba?

Answer:

Hydra reproduces by budding where an outgrowth arises from the parent and develops into a new individual. Amoeba reproduces by binary fission in which the division of nucleus is followed by division of the cell resulting in two individuals.

Question 20:

State whether the following statements are true or false. If false, correct the statement:

  1. External fertilisation can occur both in water and on land.

  2. The eggs of fish are covered by hard shells for protection.

  3. Human egg has a head, middle piece and tail.

  4. In adult human females, a single mature egg is released into an oviduct every month.

Answer:

  1. External fertilisation can occur both in water and on land. (False)

    Hint: External fertilisation occurs only in water.

  2. The eggs of fish are covered by hard shells for protection. (False)

    Hint: The eggs of fish are covered by a jelly for protection.

  3. Human egg has a head, middle piece and tail. (False)

    Hint: Human sperm has a head, middle piece and tail.

  4. In adult human females, a single mature egg is released into an oviduct every month. (True)

Question 21:

Why do only male gametes have a tail?

Answer:

Because they have to be motile and reach the non-motile female gamete