In three to five sentences, explain why sickle cell disease became so prevalent in certain east african populations.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms

the answer is d p: cell, q: organ, r: organ system, s: tissue