class X assignment on sexual reproduction

 

Question. 1(i) What is fertilisation? Distinguish between external fertilisation and internal fertilisation.

(ii) What is the site of fertilisation in human beings?
Answer.
(i) Fertilisation is defined as the fusion of a male gamete (sperm) with a female gamete (an ovum or egg) to form a zygote during sexual reproduction.

Question.2 Define the terms unisexual and bisexual giving one example of each.
Answer. Unisexual is the plant whose flowers contain either stamens or carpels but not both. Example: Papaya, Watermelon.
Bisexual is the plant whose flowers contain both stamens and carpels. Example: Hibiscus, Mustard.

Question.3 Differentiate between ‘self-pollination’ and ‘cross-pollination’. Describe double fertilisation in plants.
Answer.

During fertilisation in plants, the following events take place:
(i) One of the male gamete fuses with the female gamete present in the embryo sac.
(ii) The other male gamete fuses with the two polar nuclei in the embryo sac.
The first fusion product gives rise to the zygote while the second one forms the endosperm.
The process of two fusions occurring in the embryo sac is called double fertilisation.