Why do human causes of global change occupy a larger portion of the global change model then non human causes

answer; ///i believe that the correct answer is (the worksheet);

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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the offspring would all be white. if the parents are both white flowers then they have the genotype rr, which when crossed results in an all white punnet square.