Question

Describe the three stages of sexual reproduction and mention the major events in each of them?

Answer 1

Sexual reproduction is a natural way of reproduction in humans, animals and also in most of the plants. It can be divided into 3 main stages which are pre-fertilization, fertilization, and post-fertilization.

Complete answer:
Sexual reproduction is the type of reproduction that involves the fusion of gametes such as sperm or egg cells with a single pair of chromosomes (haploid) that combines with another to form an organism with two pairs of chromosomes that is diploid.
Three stages of sexual reproduction:

Pre- fertilization
Fertilization
Post-fertilization
Pre-fertilization involves the fusion of the gamete formation and the transfer of gametes. They are the haploid cells. The male gamete is sperm, and the female gamete is called ovum or egg. The egg or ovum is the immobile in nature so the male gametes needs to be transferred by the process of fertilization.
Fertilization is the process where haploid male and female gametes meet and fuse together to form a zygote. The zygote is diploid in nature. The process or fusion of gametes can occur either inside of the body or the outside of the body. The fusion occurring inside of the body is called internal fertilization and the outside fusion is known as external fertilization.
After fertilization, the zygote divides mitotically and develops into an embryo by the process called embryogenesis. During this process, the cell differentiates and modifies. These events are the parts of post-fertilization. Mainly the development of the embryo takes place in this stage.

Note:
Animals are divided into the oviparous and viviparous based on the formation of zygote development outside or inside of the body. During sexual reproduction the ploidy level gets changed from haploid to diploid that is from n to 2n.
n + n = 2n
(Male) + (female) = (zygote)