Only the successful competitors will reproduce, mortality<span> is very high. Four (4) conditions for natural selection. Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population.</span>
<span>Factors that affect 'neurotransmission' are plentiful, but the most common include genetics, eating habits, exposure to chemicals, and in the case of humans, stress.</span><span> </span>
