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An action potential arrives at a presynaptic neurone, which causes calcium ion channels to open. Calcium ions enter the presynaptic knob, which causes synaptic vesicles containing neurotransmitter to deta...
DNA is double stranded while RNA is a single stranded polynucleotide chain. In DNA the pentose sugar is deoxyribose (one less oxygen containing hydroxyl group) and in RNA it is ribose. In DNA the four bas...
A barrier separates the original population into two groups. Due to the different environmental conditions (selection pressures) either side of the barrier, different alleles are selected that better adap...
Enzymes are substrate specific proteins which act as biological catalysts and as temperature increases, we see an increase in enzyme activity. This occurs because an increase in temperature causes molecul...
A receptor detects a stimulus e.g. pressure. The receptor generates electrical signals. Neurones conduct impulses, a sensory neurone conducts to the spinal cord. There is a synapse between the neurones an...
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