All of these organisms, even those that are intermittently active day and night still have functioning circadian clocks and all of them still require sleep [ 2 ]. The variety of sleep patterns illustrates that whatever the ultimate cause for sleep is, it does not require a single prolonged period of rest, as in humans, and is obviously not dependent on any particular sleep architecture. Even animals that are in a niche that allows day and night activity have not given up the need for sleep, showing how fundamentally important it is.
All animals, for example need to retain the ability for arousal during sleep, but to different amounts and in different ways depending on their circumstances. Unihemispheric sleep is another example of how sleep has been adapted to specific needs [ 19 , 30 , 31 , 32 ].
Evolution has allowed for a variety of ways to spend the day and night, within which the ultimate need for sleep persists, yet has no direct control over. Learning is an essential process of the human species, and sleep is essential to the consolidation of memories.
Yet, it is not sleep, but rather sleep architecture that has co-evolved with learning and other recuperative processes to its present state, to optimize these processes for each species. One advantage this theory has over others is that it can be broadly applied to all species, from unicellular organisms all the way to Homo sapiens. This theory can be extended to other biological rhythms: There are of course two examples of periodic and predictable changes in environment, the diurnal and the seasonal.
While his article is mostly concerned with human activity, nearly all life on Earth is subjected to the same temporal constraints. Triggered by changes in light, temperature and moisture, animals and plants, by well understood biochemical processes, change their biology to survive in the two climates [ 34 , 35 , 36 ].
Deciduous trees lose their leaves and go into a hibernation mode to survive the winter, while evergreen trees change the chemistry of their internal fluids to keep from freezing [ 37 ].
Many animals go through similar changes, such as hibernating or changing color to blend in to different surroundings. These examples illustrate that when an organism is faced with periodic and predictable environmental changes, in order to survive in both environments, it must periodically change either 1 its biology; or 2 its surroundings; or 3 both.
Migrating birds, mammals and insects effectively change their environment seasonally. Why do some birds fly south for the winter? Not simply to stay warm. They fly south to prevent genetic adaptation to the winter, which would compromise their physiology and fitness in the summer. Similarly some animals hibernate not just to avoid the cold winter, but to keep from adapting to it. Honeybee workers in winter live months rather than weeks to avoid having to raise brood during the cold winter [ 35 ].
Why do some trees lose their leaves in the fall? The mechanisms and evolutionary advantages of this process, known as abscission, are well understood [ 38 , 39 ]. It takes a lot of energy and material to make a leaf; trees would not give them up without a very good reason.
Evergreen trees of course do not shed, but fundamentally change the physiology of their needles in the winter [ 37 ]. Humans today have the technology to control their environment to a large extent. If we so choose we could live in a world of constant light or constant darkness. This behaviour keeps us in sync with the sunlight. Our circadian clocks, are, by the process of entrainment, constantly resetting to changes that occur with the seasons, our schedules, or with daylight savings time.
Adaptive theories of sleep have never really taken hold, while research on recuperative, physiological theories has exploded, possibly due to the fact that recuperative theories are so much more testable than adaptive.
This new theory may open a window for experimentation. While difficult, my theory is testable, both by experimental and investigative methods. If we had evolved on a planet with no day night cycles would we still sleep?
Unfortunately we are a long way from being able to perform that experiment now, if ever. For seasonal variation the experiment has been done: Do organisms that live in constant climates need to change physiology twice each year?
Of course not — why would they need to? Sleep is a tactic evolution uses to serve a greater strategy: We sleep to allow adaptation into two competing niches. The need for sleep forces us to change our physiology into a different state for the second niche. All the other answers why we NEED sleep are but mechanisms to achieve this goal. Walker M. Simon and Schuster Inc. Cirelli C, Tononi G. Is Sleep Essential? PLoS Biol. All theories can be replaced by better ones if and when they are discovered.
Some current theories about competition these days is that it is all about winning when that is truly not the case. Losing or even coming after first place is just as important as winning and makes you a much better person in the long run. Well, there are many theories of how the dinosaurs were wiped out, and different reasons to believe different theories. Most people believe the dinosaurs were wiped out by a meteor because it makes the most sense.
There was a huge crater found that people believe is the spot where the meteor hit. It also makes sense because of the Loch Ness Monster. The Loch Ness Monster is probably a Pleasieousaurus left over from millions of years ago. But no one will ever know for sure what killed the dinosaurs They all, also, have different mass 's. Despite all the 'theories' not knowing the reason for its structural form, and why so much effort was expended I guess. The answer will depend on different from WHAT?
Log in. Literature and Language. Study now. See Answer. Best Answer. Study guides. Literature and language 20 cards. What is an omniscient narrator. What is an example of direct characterization. What would be a good topic sentence for an illustration paragraph. Which of the following would be a good topic sentence for a process paragraph paragraph.
Literature and Language 20 cards. A reader who's invested and emotionally involved in the story. With which statement would the author most likely agree. The introduction of new technology such as the electroencephalograph EEG has allowed scientists to look at and measure electrical patterns and activity produced by the sleeping brain.
While we can now investigate sleep and related phenomena, not all researchers agree on exactly why we sleep. Sleeping patterns tend to follow a fairly predictable schedule and experts agree that sleep plays an essential role in health and wellness.
A number of different theories have been proposed to explain the necessity of sleep as well as the functions and purposes of sleep. The following are three of the major theories that have emerged. According to the repair and restoration theory of sleep, sleeping is essential for revitalizing and restoring the physiological processes that keep the body and mind healthy and properly functioning.
This theory suggests that NREM sleep is important for restoring physiological functions, while REM sleep is essential in restoring mental functions. Support for this theory is provided by research that shows periods of REM sleep increase following periods of sleep deprivation and strenuous physical activity. In researchers have uncovered new evidence supporting the repair and restoration theory, discovering that sleep allows the brain to perform "housekeeping" duties.
In the October issue of the journal Science , researchers published the results of a study indicating that the brain utilizes sleep to flush out waste toxins.
This waste removal system, they suggest, is one of the major reasons why we sleep. It's important to realize, however, this study was done on mice and not humans. Earlier research had uncovered the glymphatic system, which carries waste materials out of the brain.
According to one of the study's authors, Dr. Maiken Nedergaard, the brain's limited resources force it to choose between two different functional states: awake and alert or asleep and cleaning up. They also suggest that problems with cleaning out this brain waste might play a role in a number of brain disorders such as Alzheimer's disease. Evolutionary theory, also known as the adaptive theory of sleep, suggests that periods of activity and inactivity evolved as a means of conserving energy.
According to this theory, all species have adapted to sleep during periods of time when wakefulness would be the most hazardous. Support for this theory comes from the comparative research of different animal species. Animals that have few natural predators, such as bears and lions, often sleep between 12 to 15 hours each day.
Zhang W, Guo B. Freud's dream interpretation: A different perspective based on the self-organization theory of dreaming. Front Psychol. Sleep deprivation and deficiency. Your Privacy Rights. To change or withdraw your consent choices for VerywellHealth. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page. These choices will be signaled globally to our partners and will not affect browsing data.
We and our partners process data to: Actively scan device characteristics for identification. I Accept Show Purposes. Table of Contents View All. Table of Contents. Restorative Theory. Adaptive Theory. Energy Conservation. Brain Plasticity. Frequently Asked Questions. Allen Rechtschaffen Sleep can be understood as fulfilling many different functions but intuition suggests there is one essential function. The 4 Stages of Sleep. How to Get Better Sleep. Declining Sleep Needs Newborns need between 14 and 17 hours of sleep per day.
Was this page helpful? Thanks for your feedback! Sign Up. What are your concerns? Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.
Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Related Articles.
Causes of Vivid Morning Dreams. What Is Sleep Architecture?
0コメント