The process by which an organism produces its offspring is called reproduction. Reproduction is necessary to continue the lineage of an organism.
There are two types of reproduction in animals, viz. sexual and asexual reproduction.
The male reproductive organs are a pair of testes, two sperm ducts and a penis. Testes produce the male gametes which are called sperms.
Structure of Sperm: A sperm is very small in size, unicellular, and is composed of a head, middle piece and a tail.
The female reproductive organs are a pair of ovaries, a pair of oviducts (fallopian tubes) and a uterus. The female gametes, i.e. eggs are produced by ovaries.
Fusion of a male gamete with a female gamete is called fertilization. During fertilization, fusion of nuclei of sperm and egg takes place. Zygote is formed after fertilization.
There are two types of fertilization in animals, viz. external fertilization and internal fertilization.
It takes place in the female reproductive system through following steps:
Gestation: The period from conception to child birth is called gestation period. The gestation period in humans is of 40 weeks.
Embryo: After conception, the ball of cells undergoes further rounds of cell division. During the process, the cells begin to differentiate into different types of tissue. Tissue level stage after conception is called embryo.
Foetus: When the embryo begins to resemble a human being, it is called a foetus. At this stage, various external organs; like legs, head, ear, eyes, etc. become apparent.
IVF (In Vitro Fertilisation): Any biological process carried out in laboratory is called in-vitro. Thus, fertilization carried out in laboratory is called in-vitro fertilization. After in-vitro fertilization, zygote is allowed to develop into a mass of cells and is then transferred into the uterus for subsequent development. Many women may fail to conceive due to certain problems. In-vitro fertilization helps such women to bear a child. A baby which is born with the help of this technique is often called the ‘test tube baby’.
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