Evolutionary theory of sleep

AO1
Ecologist theories propose that sleep is necessary to keep animals inactive when they do not need to engage in avtivities essential for their survival. 
Meddis argues that sleep is important in order to be protected against predators. These animals in danger of predators sleep less than predators to remain alert.

AO2
Pilleri - Research support - Dolphins in the River Indus are in constant danger from floating debris so only sleep for a few seconds at a time
Mukhametov 1984 - Studdied bottlenose and porpoise dolphins - They are able to switch off one of their cerebral hemispheres at a time enabling them…