Reproduction in Animals

Introduction

· Reproduction is the most essential for the continuation of a species.

· Reproduction ensures the continuation of similar kinds of species, generation after generation.

Modes of Reproduction

· Following are the two modes of reproduction −

o Sexual reproduction

o Asexual reproduction

· Let us discuss each one separately −

Sexual Reproduction

· In animals, males and females have different reproductive organs.

· The reproductive parts in animals produce gametes that fuse and form a zygote.

· The zygote develops into a new similar species.

· The type of reproduction through the fusion of male and female gametes is known as sexual reproduction.

· The male gametes, produced by testes, are known as sperms.

· The female gametes, produced by ovary, are known as ova (or eggs).

· In the process of reproduction, the first step is the fusion of a sperm and an ovum (egg).

· Fusion of the egg and the sperm is known as fertilization (as shown in the above image).

· During the fertilization, the nuclei of the sperm and the egg fuse together and form a single nucleus that result into the formation of a fertilized egg also known as zygote (shown in the image given below).

· The zygote further divides repeatedly to give rise to a ball of cells that begin to form groups. The groups develop into different tissues and organs constituting a full body. In the process, the developing structure is known as an embryo (shown in the image given below).

· The embryo continues to develop in the uterus and develops body parts such as head, face, ear, eyes, nose, hands, legs, toes, etc.

· The stage of the embryo in which different parts of the body develop and can be identified is known as foetus (shown in the image given below).

· In a defined period of time, when the development of the foetus is complete, the mother gives birth to the baby.

· The animal which gives birth to young ones is known as viviparous animal. E.g. Human, cow, dogs, etc.

· The organism that lays eggs is known as oviparous animal. E.g. all birds (except bats), lizard, etc.

Asexual Reproduction

· The type of reproduction in which only a single parent, gets divided into two new offspring, is known as asexual reproduction. E.g. Hydra and Amoeba.

· In hydra, the individuals develop from the buds; therefore, this type of asexual reproduction is known as budding (shown in the image given below).

· In amoeba, nucleus gets divided into two nuclei; therefore, such kind of asexual reproduction is known as binary fission.

Cloning

· Cloning is the modern science technique to produce an exact copy of a cell, any other living part, or a complete organism.

· For the first time, cloning of an animal was successfully performed by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland.

· In 1996, they cloned successfully a sheep and named that Dolly.