What substance in the upper atmosphere blocks ultraviolet radiation from the sun, making life on land possible?

a: the sheep and waste material both release carbon into the atmosphere.

identify the dna change shown in the diagram and explain how that change can result in the increased genetic diversity often seen among siblings.

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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where is the diagram?

if you insert the diagram ill be able to you