Flashcards in Ecological theory Deck (12)
nightime was a time of danger for our ancestors so we sleep to keep us safe from danger. We couldn't safely forage at night so sleep gave us an adaptive advantage by keeping us out of harms way. Those members of the species that slept were more likely to have survived to maturity and so pass on their genes. Decoursey supports that sleep is an adaptive feature and helps with protection. He removed the SCN of chipmunks, they developed a new sleep-wake cycle so they were awake at night and hence attracted predators and died.
You would expect species most at risk to sleep for longer but those at risk such as herbivores sleep least whilst species at least risk sleep most. Food intake theory is used instead to explain his. The lion feeds once every few days and so spends the rest of its time asleep, because it can. Herbivores with their diet of grass need to be eating all the time so dont have time to sleep
Evaluation of Meddis-Why do those at most risk sleep?
If the ony purpose of sleep is protection, why do those at most risk sleep? Research in India suggest that lions are happier killing someone asleep as opposed to active. Disputing the protection theory because they are not protected when they are asleep.
Evaluation of Meddis-Indus dolphins
These are at constant risk from debris but still manage to grab few seconds of sleep by doing this it's rising its life. How is this protective? They have lost their sight die to evolution, why haven't they lost sleep?
sleep is an adaptive behaviour to conserve energy.During sleep, body temperature falls and the animal is inactive. Therefore less energy is used. The more at risk we are from predators, the longer we will sleep. In early species at times when we would have been unable to forage, sleep would have been a way of conserving our resources by lowing our metabolic rate.
Webb Evaluation- Research has shown
that energy metabolism is reduced during sleep. However, it is estimated the calories we save is equivalent to a piece of bread
General evaluation-adopted a catch all approach
The theories do not attempt to explain the sleep patterns of various species, however, if one theory will not work/fit with their findings then another theory will.
General evaluation- why do we become deprived?
Is sleep serves no other purpose than safety, why do we suffer psychological problems? Such as the cats and rats not sleeping due to conditioning of REM sleep
General evaluation-waste of time?
Empson describes sleeps as a complex function of the brain. He refers to the evolutionary theories as a 'waste of time.'
General evaluation-unable to explain complexities of sleep
Why do we have 5 stages of sleep? In an attempt to explain REM in evolutionary terms, it has been suggested that active sleep is most prominent in birds and mammals- both warm blooded. Perhaps REM keeps the brain active and prevents it from dropping to low levels
General evaluation-artificial light
Artificial light has allowed us to see at night so we are able to protect ourselves against harm at night