Once atp donates its phosphate to a coupled reaction it becomes adp. The adp.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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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.

"it built up in the atmosphere"

i think thats it, idk, i tried looking for this exact q& a for grad. and idk if i got this question right or sorry if im wrong

answer; ///(a) ;