Q1. It is well known that rubbing a minor wound inhibits the sensation of pain that an individual is experience. Please design a circuit that would explain this phenomenon (i.e., how would you put together a set of neurons in the spinal cord or beyond to mediate this process). What adaptive function might this phenomenon serve?

Q2. In hypothetical environment, fishes called pike-cichlids are visual predators of algae-eating fish, such as they locate their prey by sight. If a population of algae eaters experiences predation pressure from pike-cichlids, which would least likely be observed in the algae-eater population over the course of many generations?