The differences in characteristics between individual organisms, or groups of organisms of any species is called variation.

The variation in species can be genetic differences, the effect of environmental or a mixture of both.

There are two types of variation: continuous and discontinuous variation.

Human height and weight is an example of continuous variation.

Human blood group is an example of discontinuous variation.

All variants arise from mutations and most have no effect on the phenotype.

A mutation is a change in a gene or chromosome. Mutations arise continuously.

Variation between different species is generally higher than the variation within a species.

The combining of genes from the mother and father creates genetic variation.

Children usually look a little like their father, and a little like their mother, because they get half of their DNA and inherited features from each parent.

Examples of inherited variation in Humans are: hair colour, eye colour and skin colour.

Variation caused by the surroundings is called environmental variation.

Examples of environmental variation in human are: body mass or skin color and your language.

Evolution is a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.

Theory of Evolution: All species have evolved from simple life forms that first developed more than three billion years ago.

Natural selection is a process where organisms that are better adapted to an environment will survive and have more offspring.