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Natural selection is when certain characteristic are 'selected' for. Each species have simiar characteristics but differences in genes means that their characteristics can vary for example individual bird...

Diffusion is the spreading out of particles of any substance in solution or of gas resulting in a net movement of an area of high concentration to an area of low concentration. Diffusion is key to the sur...

Four characteristics of an efficient respiratory surface are: thin epithelium, large surface area, abundant capillaries, ventilation mechanism.

The kidney is able to filter blood as it is made up of about a million filtering units. These units are called nephrons which are assosiated with capillaries. The blood flows to the glomerulus, which is a...

To start, it is important to have a clear understanding of what an enzyme is. An enzyme is a biological molecule which speeds up the rate of a reaction without being changed or used up in the process. Eac...