Outline and Evaluate the Evolutionary Theory of Sleep (8+16 Marks)

1134 Words Apr 9th, 2014 5 Pages
The basis of the evolutionary theory is that animals sleep because it serves some adaptive function. The notion of the adaptive nature of sleep comes from the theory of evolution. The idea is that any behaviour that has continued into an animal’s gene pool must have been naturally selected because it has, in some way, aided the survival and reproduction of the animal that possesses that characteristic.
One explanation of sleep that the evolutionary theory proposes is that it helps to conserve energy, particularly in warm blooded animals such as mammals which use a considerable amount of energy to maintain their body temperature - This especially true from animals with high metabolic rates such as mice. According to the theory, sleep
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The theory predicts a negative correlation between body size and sleep which is supported by Zepelin and Rechtschaffen, who found smaller animals sleep more than larger animals, although there were some exceptions such as sloths that are large and sleep a lot. However, this research is not supported by Capelini et al who found a positive correlation. The study used standardised data and had a more robust design as it was a laboratory experiment with controlled conditions and so may therefore be more reliable than the older evidence.
Another explanation the theory proposes is the idea that if sleep is necessary then the time spent asleep conserving energy is constrained by foraging requirements. The foraging requirements theory predicts a trade-off between foraging needs and sleep. For example, Capellini found that animals with a greater need for foraging because of a high metabolism or diet low in energy had lower sleeping rates, such as herbivores that have to spend a lot of time eating because their food is poor in nutrients, supporting the foraging requirements explanation for sleeping patterns. The evolutionary approach suggests we sleep because it is adaptive otherwise all animals there is a question as to why all animals do it and why their sleep patterns differ. This suggest that these patterns are adaptive to the species surroundings. The phylogenetic scale provides support for the evolutionary nature of sleep as the fact that animals that are close

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