Evolutionary Explanations

Question 1

Energy conservation:

Answer 1

Warm blooded animals use energy to maintain temperature, such as birds and mammals. This is true for small animals with a high metabolic rate such as mice.
Sleep provides a period of inactivity to conserve energy, such as hibernation. Small animals should sleep lots to conserve energy.

Question 2

Foraging requirements:

Answer 2

Time spent asleep is constrained by the time spent eating.
Herbivores (cows) need to eat lots as there food is low in nutrients
Carnivores (lions) can afford to sleep more as their food is high in nutrients

Question 3

Predator avoidance

Answer 3

Time spent asleep is constrained by risk of predation (being eaten).
Predators can sleep for longer as they aren’t at risk
Prey sleep less and are in danger when they sleep so they sleep when they are less vulnerable such as at night when they can hide

Question 4

Waste of time

Answer 4

Sleep is wasting time and animals sleep because they have nothing else to do, such as eat, mate and hiding from predators.
For most animals involves sleeping at night and sleeping out of sight as they aren’t as vulnerable while they’re sleeping.
Being awake is dangerous not just because of predation but because they could get injured (Siegel)

Question 5

AO2

Answer 5

Zepelin and rechtschaffen found smaller animals with higher metabolic rates did sleep more than larger animals supporting the idea of energy conservation for sleep but there are exceptions. For example, sloths sleep for 20 hours a day which contradicts this theory.
Capellini et al suggests that the energy conservation hypothesis may be wrong and the foraging and predator avoidance may be right. They argued that previous research methods may be flawed because methods used to collect data were not standardised and so comparison between species were meaningless and low internal validity. They found a positive correlation between body size and sleep.

Alison and cicchetti found that species with a higher risk of predation did sleep less but there were exceptions. Rabbits slept as much as moles even though they were at risk of predation. So this goes against the predator avoidance theory.