Psychology Unit 3 - Evolutionary explanation for sleep, sample essay

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INTRO - Sleep is a natural, periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, resulting in a decrease in bodily movement and responsiveness to external stimuli. There are several explanations for sleep, one of which being the evolutionary explanation.

AO1 - The evolutionary explanation (also referred to as the ecological approach) is based on the observation of animals in their natural enviroment. It states that there are several benefitial consequences to sleep. For example, it allows for energy conservation; it provides a period of time where there is no activity, thus allowing the conservation of energy which is essential for animals with high metabolic rates, and WEBB went as far to suggest this as being the hibernation theory of sleep. There is also the suggestion that the amount of sleep is conditional upon the foraging requirements of the animal. For example, herbivores, such as horses, rely much upon plants for food (ie, grass), which is relatively low on nutrients; therefore, they cannot afford to spend much time sleeping as they need to spend more time eating. In contrast, carnivores, such as dogs, eat food which is high in nutriants, and therefore can afford to spend more time sleeping. As well as these foraging requirements, sleep is also constrained by predator avoidance; generally, predators can afford to sleep more as they are not being hunted. Prey, however, need to remain vigillent as to avoid being eaten, therefore are to sleep less, and sleep when they are less vunerable. Finally, sleep is also described in this theory as being a method of wasting time; it is a way of staying still when foraging is not an option and an animal is subject to predation. This idea was initially proposed by MEDDIS, and later supported by SIGEL's view that being awake is riskier than being asleep,

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