Reproduction II – Sexual Reproduction SS2 Biology Lesson Note

 SEXUAL REPRODUCTION

Sexual reproduction involves two parents of different sexes (male and female). Each parent produces gamete male and female gametes respectively. There is meiosis during which the number of the chromosomes is halved i.e. from diploid to haploid in the formation of gametes. The egg cell (female gamete is large and non-motile). The sperm (male gamete) is motile and small. During fertilization, the two haploid gametes (male and female) fuse to form a diploid zygote. The zygote undergoes repeated cell division and forms an embryo. The embryo undergoes repeated cell division and differentiation and develops into a young organism similar to the parents.

There are two types of sexual reproduction, they are: 

1. Conjugation which occurs in paramecium and spirogyra.
2. Fertilisation which occurs in higher plants and animals.
3. Conjugation In Spirogyra

In spirogyra, two filaments lie close to each other and outgrowths appear on the walls of the cell lying opposite one another. The cells meet and their walls break and a conjugation tube is formed. One of the gametes passes through the conjugation tube and merges with the gamete in the other cells and their nuclei unite. This results in the formation of a zygospore.

The zygospore can withstand dry conditions and can germinate into a new individual when moisture labels. This process of reproduction is called. It also occurs in mucor.

Differences Between Asexual Reproduction And Sexual Reproduction