Question

in the range of tolerance graph below, which letter (or letters) represent a zone of physiologic stress? a and e b and d c

Explanation:

In a tolerance graph, the zone of physiologic stress is where the population is not at its optimal level. For a population - gradient graph, the areas \(A\) and \(E\) represent the zones where the gradient (environmental factor) is at the extremes (low and high respectively). At these extreme gradient values, the population experiences physiologic stress as it is not in the optimal range (where the population is highest, which is around zone \(C\)). Zones \(B\) and \(D\) are transitioning zones towards the optimal and extreme conditions, but \(A\) and \(E\) are clearly at the extreme gradient values where stress is maximum.

Answer:

A. A and E