Explain two theories for why we sleep described in your textbook. Provide evidence which supports each theory and examples

What will be an ideal response?

Answer: A good answer will include both of the following key points.
? Restore and repair hypothesis—the idea that the body needs to restore energy levels and repair any wear and tear on the body from the day's activities. Research on sleep deprivation clearly shows that sleep is a physical and psychological necessity. A lack of sleep eventually leads to cognitive decline, emotional disturbances, and problems with the immune system. For some species, sleep deprivation can be more fatal than food deprivation.
? Preserve and protect hypothesis—suggests two more adaptive functions of sleep: preserving energy and protecting the individual organism from harm. To support this hypothesis, researchers cite that the animals most vulnerable to predators sleep in safe hideaways and during the time of day when they are most susceptible. For example, humans and other visually-oriented creatures sleep at night when it is dark. This is adaptive because it is potentially dangerous for us to be active in the dark.
? Brain plasticity and Function—Sleeping and dreaming have cognitive benefits. Memories are consolidated during sleeping and dreaming and adaptive changes in the synaptic spaces between neurons take place during sleep. Conversely, sleep deprivation disrupts functioning of the hippocampus, which is a critical brain region for memory.