Functions of sleep

AQA, Functions of sleep (evolutionary/ecological)

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  • Created by: holly
  • Created on: 10-06-12 18:09


Focusses on Ecological Niches: Environment, predator-prey status, size and sleep site.

Environment: Whether they are diurnal or nocturnal

Predator prey status- Prey animals are often herbivores and are more vulnerable than predators, expecially when asleep. 

Sleep site- Exposed? or in a burrow

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Ecological factors

Predator prey status- Meddis, Sleep keeps vulnerable prey animals safe at times when normal activities are impossible. Diurnal animals cannot forage for food at night so simply stay out of harms way by sleeping.

Hibernation theory, Webb, uses the analogy of hibernation to explain sleep. Animals such as bears and squirrels hibernate over winter to conserve energy at times when hunting and foraging for food is impossible. Similarly, sleep is a time of relative inactivity when animals will conserve energy resources. This is particularly important for small animals such as mice who tend to have a high metabolic rate.

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Allison and Cicchetti studied sleep in 39 animal species and found that prey animals sleep for significantly less time than predators. This might imply that sleep is a dangerous time for prey animals and goes against Meddis' idea.

Prey animals are oftern herbivores and have been shown to sleep for less time than carnivores (Lesku et al) so it might be this fact that explains the predator-prey relationship.

Sleep leaves an animal unreactive and vulnerable. If safety was the only consideration then it would be far more effective to stay awake and alert but quiet rather than to fall asleep.

Support for Webb

Findings show that basal metabolic rate (BMR) is positively correlated with sleep time (the higher the metabolic rate, the more sleep) Zepelin and rechstaffem, berger and phillips Smaller animals have a higher metabolic rate, therefore sleep more.

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Lesku: Brain mass is positively correlated with the amount of REM sleep, but it has no association with NREM. (Supports Oswald, against Horne who argued that both were for restoration of the brain)

Herbivores sleep for less than carnivores

Animals with more exposed sleep sites, sleep less. more dangerous.

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It takes the whole animal and it's lifestyle into account. It is not a reductionist approach, but holistic in that sense, but it tries to explain sleep in terms of the whole animal and it's environment. 

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