RationalWiki's 2020 Fundraiser

There is no RationalWiki without you. We are a small non-profit with no staff – we are hundreds of volunteers who document pseudoscience and crankery around the world every day. We will never allow ads because we must remain independent. We cannot rely on big donors with corresponding big agendas. We are not the largest website around, but we believe we play an important role in defending truth and objectivity.

If everyone who saw this today donated $5, we would meet our goal for 2021.

Fighting pseudoscience isn't free.
We are 100% user-supported! Help and donate $5, $20 or whatever you can today with PayPal Logo.png!

Donations so far: $720Goal: $3500


From RationalWiki
Jump to: navigation, search
The poetry of reality
Icon science.svg
We must know.
We will know.
A view from the
shoulders of giants.

Homeostasis (Latin: homeo-, "similar to"; stasis, "a standing still")[1] is a steady state (a system that does not stray away from a range of favorable conditions, maintaining a relative constancy) in which processes exert positive and negative control over the variables in a system. In other words, it is a system that remains in a certain range of stability, with certain factors affecting it while also responding to the changes in order for the system to remain more or less the same. A prominent example of such would be our body temperature: for the most part, humans maintain a fairly constant temperature of 37° C (98.6° C for the Americans). If it is cold outside, the body generates heat in order to preserve that temperature internally; if it is a hot day outside, sweat is produced which later evaporates and thus cools the body.[2] In biology, there are four categories of homeostatic control.


These processes regulate and maintain the internal environment of a cell or an organism. Each process involves:

1) A sensory device that monitors the value of a variable
2) An input from the sensor to an effector whenever the value changes beyond a set threshold
3) An effector that restores the value of the variable to normal and stops the original input (negative feedback)

Examples of physiological homeostasis include the control of blood sugar levels, heart rate, and body temperature.

Illustration of homeostasis in regards to blood sugar levels.


These are the processes that control disturbances in developmental conditions, ensuring that the fitness of the organism is not impaired.


This describes the tendency for species to resist the effects of artificial selection, in order to maintain genetic composition.


There are some ecological processes that are considered homeostatic, such as the regulation of population density and diversity.


  1. https://www.etymonline.com/word/homeostasis
  2. Urry, Lisa A. (2016). "Basic Principles of Animal Form and Function". Campbell Biology 11th ed. Pearson. pp. 879. ISBN 0-134-09341-0.