Question

How does reproduction take place?

Answer 1

There are two modes by which all living organisms reproduce.
These are (i) Sexual reproduction, and (ii) Asexual reproduction.

Sexual Reproduction
In animals, males and females have different reproductive parts or organs. Like plants, the reproductive parts in animals also produce gametes that fuse to form a zygote. It is the zygote which develops into a new individual. This type of reproduction beginning from the fusion of male and female gametes is called sexual reproduction.

Male Reproductive Organs
The male reproductive organs include a pair of testes (singular, testis), two sperm ducts and a penis. The testis produces the male gametes called sperms. Millions of sperms are produced by the testes. Though sperms are very small in size, each has a head, a middle piece and a tail. Each sperm is a single cell with all the usual cell components.

Female Reproductive Organs:
The female reproductive organs are a pair of ovaries, oviducts (fallopian tubes) and the uterus. Ovary produces female gametes called ova (eggs). In human beings, a single matured egg is released into the oviduct by one of the ovaries every month. Uterus is the part where development of the baby takes place. Like the sperm, an egg is also a single cell.

Fertiliztion:
The first step in the process of reproduction is the fusion of a sperm and an ovum. When sperms come in contact with an egg, one of the sperms may fuse with the egg. Such fusion of the egg and the sperm is called fertilization. During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilized egg or zygote.

Development of Embryo

Fertilization results in the formation of zygote which begins to develop into an embryo. The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is termed an embryo. The embryo gets embedded in the wall of the uterus for further development.

The embryo continues to develop in the uterus. It gradually develops the body parts such as hands, legs, head, eyes, ears, etc. The stage of the embryo in which all the body parts can be identified is called a foetus. When the development of the foetus is complete, the mother gives birth to the baby.

Asexual Reproduction
The type of reproduction in which only a single parent is involved is called asexual reproduction.
1) In hydra, new individuals develop from buds. This method of asexual reproduction is called budding.
2) Amoeba reproduces by dividing itself into two. This type of asexual reproduction is called binary fission.