Evolutionary Explanations
Evolutionary Explanations of sleep:
-Energy conservation
-Predator avoidance
-Foraging requirements
-Waste of time
- Created by: Jodie-Leigh
- Created on: 31-05-14 02:03
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- Evolutionary Explanations
- Foraging Requirements
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- Time spent sleeping may be constricted by food requirements as an animal has to spend time gathering food.
- Herbivores spend a lot of time eating so sleep less
- Carnivores eat higher nutrient foods so can afford to eat less and spend time sleeping.
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- Tigers sleep for 15.8 hours whist cows sleep for 3.9 hours.
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- Waste of Time
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- Sleep helps animals stay away from predators when they're most vulnerable and don't need food.
- Most animals sleep whilst it's dark, as it's riskier to stay awake and hunt when it's dark
- Save energy and stay away from danger.
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- Horne - very little difference in energy conserved when we are asleep to when we are awake and resting.
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- Predator Avoidance
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- Predators can sleep longer than prey - not at risk.
- Prey do sleep though, so there must be an evolutionary advantage.
- Prey sleep when they're least vulnerable
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- Dolphins sleep with half a brain at a time.
- Adapted so that they an stay safe
- One species of Dolphin only sleep for a few seconds at a time
- Less likely to be injured by debris
- Dolphins sleep with half a brain at a time.
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- Energy Conservation
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- Activities use energy, animals with high metabolic rate use even more energy.
- Sleep provides period of forced inactivity to conserve energy.
- Some animals hibernate to conserve energy.
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- 53 species of mammals studied, those with high metabolic rates slept for longer. Smaller animals also slept for longer.
- E.g A brown bat sleeps for 20 hours, whilst an elephant sleeps for 4 hours.
- A sloth has slow mmetabolism and is large but sleeps for 20 hours
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- Overall Evaluation
- Rats on a turn table.
- Table starts to spin when their brain patters change - so they awoke and started to exercise. If they didn't they fell into the water.
- Only had 16% of their normal sleep - became weak and lost weight even when they ate normally. Metabolic rate also increased.
- Most experimental rats dies between 21-33 days
- Couldn't rest to conserve energy.
- May have died due to trauma.
- Ethics - was it worth it?
- Young - We only have sleeping patterns for 150/5000 mammals.
- Still have lots of data to collect and compare.
- Recordings are also conflicting - further research is needed.
- Rats on a turn table.
- Foraging Requirements
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