When the Isthmus of Panama formed between North and South America, some North American mammal lineages crossed to South America and underwent dramatic radiations. For terrestrial species, did the formation of the land bridge represent a vicariance or dispersal event? Did the recent construction of the Panama Canal represent a vicariance or dispersal event for terrestrial organisms?

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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answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion