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The diaphragm contacts and moves down. The intercostal muscles between the ribs contract. This causes the ribcage and the sternum to move up and out. The thorax increases in width from back to front. This...

The diaphragm contracts and flattens out, increasing the volume of the thorax and decreasing the pressure in there. This causes a pressure gradient between the thorax and the outside air, so air flows int...

Firstly, an enzyme is a specific protein with a unique shape. The main aim of an enzyme is to CATALYSE a reaction. This means, the reaction is sped up, but the concentrations of reactants or products are ...

A synapse is gap between two neurones. When a nerve impulses travels along the axon reaches the end of the pre-synaptic neurone, the release of chemical messengers (called neurotransmitters) is triggered....

Allopatric speciation occurs when two species are living in separate environments and therefore there is no gene flow between the populations. This will then cause the populations to differentiate (change...