Discuss each of the following interspecific relationships, including reference to the species involved, their role in the interaction, and the specific characteristics of the relationship:

(a) mutualism between ruminant herbivores and their gut microflora

(b) commensalism between a shark and a remora

(c) parasitism between a tapeworm and its human host

(d) parasitism between a cat flea and its host.

the answer is c) abandoned properties that are contaminated with hazardous materials.

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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