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LIFE CYCLE OF ANIMALS

All living things come into this world, they grow, reproduce and die. This whole process is known as a life cycle.

There are two main ways in which living things can reproduce themselves.

REPRODUCTION BY A SINGLE CELL.

This needs only a single parent cell to reproduce a new organism. This method of reproduction occurs in lower animals, microorganisms, and plants. This new organism is an exact copy of its parent as there is no joining of two different cells.

Some very invertebrates are made up of only a single cell. They are so small that they can only be seen under a microscope. they divide into four separate cells. The two cells divide into four, then eight and so on.

REPRODUCTION BY THE JOINING OF TWO CELLS

This requires two types of cells: male (sperm) and female (egg). When these two cells join together, fertilization takes place and a new organism is formed. This new organism has two parents and has the characteristics of both of them. So it is not an exact copy of its parents.

There are two ways in which animals can reproduce by the joining of the sperm and the egg. The young are either born alive from their mother, as is the case of mammals , or they hatch from egg, for example, in the case of birds, insects and fish.

LIFE CYCLE OF A FISH

But some animals have a very complicated life cycle. They change their appearance along with body structure when they pass through the different stages of their life cycle. The change in their body structure, from an egg to an adult, is known as metamorphosis.

You can observe this process. Notice that the

body features of frog change at every stage

There are total four stages:

An insect or animal which has three stages are called incomplete metamorphoses.

And if an insect or animal which has three stages are called complete metamorphoses.

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STUDENT AT: DAR E ARQAM