Evolutionary Explanations of Sleep
- Created by: rhallett
- Created on: 29-10-15 11:47
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- Evolutionary Explanations of Sleep
- These argue that sleep evolved to help organisms adapt to their environment; hibernation.
- Argues that sleep has NO important restorative function
- Argues that sleep has NO important restorative function
- 1) Meddis
- Sleep protects animals from harm and predation by immobolizing animals during times of risk ie night
- During evolution, humans would have slept during the night, when they would have been at risk of predation
- Sleep protects animals from harm and predation by immobolizing animals during times of risk ie night
- 2) Webb
- Sleep allows animals to conserve energy by reducing activity during times when it would not be useful
- Particularly useful for small animals with high metabolic rates and warm blooded animals ie mammals as they use a lot of energy to maintain body temperature
- Sleep allows animals to conserve energy by reducing activity during times when it would not be useful
- 3) Siegel
- Combines both theories: sleep allows energy conservation and predator avoidance
- Little brown bats show this: only awake for a few hours a day to feed - supports as it suggests sleep aids survival and energy conservation
- Combines both theories: sleep allows energy conservation and predator avoidance
- Evaluation
- + Decoursey - damaged the SCNs of 30 chipmunks, disrupted circadian rhythms; returned to wild and observed over 80 days - more were killed because they were active and noisy at night - SUPPORTS MEDDIS
- Unclear if these findings can be extrapolated to humans, sleep may have evolved to have different functions in two species
- Unethical as the chipmunks were being harmed
- Unclear if these findings can be extrapolated to humans, sleep may have evolved to have different functions in two species
- + During sleep, body temperature drops - SUPPORTS WEBB
- But the drop is very little thus little energy is conserved
- During REM the brain is very active and uses a lot of energy,
- Also unclear why animals need to be unconscious to conserve energy as this is dangerous for them
- During REM the brain is very active and uses a lot of energy,
- But the drop is very little thus little energy is conserved
- + Zepelin found smaller animals with higher metabolic rates slept more than larger animals - SUPPORTS WEBB
- Yet there are many exceptions eg Sloths who are large and sleep for 20 hours a day
- - Allison - studied 39 species, found that prey slept less than predators - DISPROVES MEDDIS
- Sleep helps animals avoid predation; small animals can hide, animals such as giraffes cannot
- One of the biggest problems is that many animals sleep, even when it appears it doesn't help them adapt to their environment
- One species of dolphin has lost its ability to see and lives in the river Ganges, yet it still sleeps. Suggests a restorative purpose of sleep
- + Decoursey - damaged the SCNs of 30 chipmunks, disrupted circadian rhythms; returned to wild and observed over 80 days - more were killed because they were active and noisy at night - SUPPORTS MEDDIS
- These argue that sleep evolved to help organisms adapt to their environment; hibernation.
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