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A nerve impulse is an electrical current that is transmitted down the axon of a neurone and to the synaptic knob. The impulse depolarises the membrane and causes a change in voltage across the membrane. T...
The body has both humoral and cell mediated immunity. A vaccination involves injecting a patient with inert (Inactivated) or dead material from a pathogen, be that a bacterium or a virus. Once injected in...
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...
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...
Carbon dioxide diffuses into the cell leaf through the stomata, and diffuses into the water surrounding the mesophyll cell walls (main site of photosynthesis-packed with many chloroplasts). From here, the...
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