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Learning objectives – to learn how DNA is present in humans and how that

reproduction occurs in humans Learn about why variation occurs in organisms

Organisms of the same species will have many differences.


This is known as variation. Variation simply occurs due to the different genes

we possess. There are two different types of variation, environmental and



Genetic variation

Genetic variation occurs due to the different genes we get from our parents. 

The genes we get from parents are due to random chance so no two offspring

will be the same, unless you are a twin!!!


In humans we get half of our genetic information for our mother and half from

our father, which is why we look like our parents The characteristics that are

determined by genetics are characteristics such as eye color, height, blood



Environmental variation

Environmental variation occurs due to the differences in the environment we

live in. The characteristics influenced by the environment are weight or

sometimes even height.


Both determine the majority of your characteristics. A prime example of this is

height as this can be determined by your nutrition but also can be determined

by genes.


Related Topics

Genes, Chromosomes And DNA           Sexual Reproduction

Asexual Reproduction                             Cloning