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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...
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...
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