This document discusses the life cycles of animals. It explains that there are two main types of reproduction: single cell reproduction which involves a single parent cell dividing to create an offspring, and reproduction through the joining of male and female cells (sperm and egg) which results in offspring with characteristics of both parents. It provides examples of animals that reproduce through live birth like mammals versus hatching from eggs like birds. The document also notes that some animals like fish undergo metamorphosis, changing their appearance and body structure as they pass through different life cycle stages from egg to adult.

1. S
LIFE CYCLE OF
ANIMALS

2. S All living things come into this world, they
grow, reproduce and die. This whole process
is known as a life cycle.
S There are two main ways in which living
things can reproduce themselves.

3. REPRODUCTION BY A
SINGLE CELL.
S 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.
S 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.

4. REPRODUCTION BY THE
JOINING OF TWO CELLS
S 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.
S 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.

5. LIFE CYCLE OF A FISH

6. S 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.

7. You can observe this process.
Notice that the body features of
frog change at every stage

8. S There are total four stages:
S An insect or animal which has three stages are called
incomplete metamorphoses.
S And if an insect or animal which has three stages are
called complete metamorphoses.

9. PRESENTED BY:
STUDENT AT:
DAR E ARQAM