Answer to Question 1
Answer: All vertebrates sleep, and sleep deprivation can be fatal for some animals. Sleep deprivation in humans can produce visual hallucinations and difficulty in concentration. During slow-wave sleep, brain activity declines, and it appears that slow-wave sleep is important for cognitive functioning. Although physical exertion (increase or decrease) has little effect on slow-wave sleep, mental exertion produces an increase in subsequent slow-wave sleep.
Answer to Question 2
Answer: Melatonin