The potentials bring the neuron closer to threshold, while the potentials bring it farther away from threshold.

it would be heredity

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

d. organisms have cells with different shapes and functions.

protistas excret ethanol used in the manufacture of vinegar