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Sleep in AnimalsAlexis Earl11/10/15
Sleep is a vital part of an organism’s life. All animals,including humans require some form of sleep.Sleep is a process of the body and mind which typically occurs for several hours each night,where the nervous system is relatively inactive, the eyes are closed, the muscles are relaxed,and the mind is in a state of unconsciousness.It is a reversible process of reduced responsiveness to external stimuli alongside with immobility.This decrease in reactivity to external stimuli is what separates sleep from wakefulness. Sleep is a natural process that has always been studied by scientists, yet not all is known on the subject. The amount of sleep needed is varied between each species. Different organisms need different amounts of sleep for their bodies to go through the correct physiological processes. In humans, the average number ofhours of sleep needed is approximately 8 hours, but that number can vary between individuals.One theory suggested is that sleep was first an adaptive mechanism used to reduce motor activityin organisms, and to escape from predators in the environment. From that theory evolved the idea that sleep is used for the brain to refresh neural circuitry. Sleep can be characterized by four different characteristics: periods of minimal movement of the body, responsiveness is reduced toexternal stimuli, rapid reversibility, and body posture that is unique to the species (Klandorf, Sherwood, & Yancey, 2013). Sleep is regulated by circadian and homeostatic processes.Circadian regulation is demonstrated through a 24-hour rhythm of sleep. Many physiologists agree that sleep serves a role in many different aspects of the body ranging from the regulation ofmetabolism and the immune system to memory consolidation. Although scientists can agree that the main function of the body is for energy, they have a hard time agreeing on what was the
original function of sleep.The reason on why sleep is needed can be broken down into three major theories:restoration and recovery, memory processing, and energy conservation.One theory on why we need sleep is that we, as human beings, sleep to conserve energy. This is a reasonable theory, but the idea of restoration plays more of an active role in the body. Perhaps in an evolution aspect, sleep stayed as an adaptation to different organisms because it was a useful process for survival. Sleep is a dangerous process for organisms in the presence of predators. In mammals, the amount of REM (rapid-eye movement) sleep, also known as paradoxical sleep, and length of sleep is lower in animals of prey rather than in predators.