Editing Ecology (section)

=== Radiation: heat, temperature and light ===
{{Anchor|Sunlight}}<!-- E.g. in [[Neritic zone]] -->
The biology of life operates within a certain range of temperatures. Heat is a form of energy that regulates temperature. Heat affects growth rates, activity, behaviour, and [[primary production]]. Temperature is largely dependent on the incidence of [[solar radiation]]. The latitudinal and longitudinal spatial variation of [[temperature]] greatly affects climates and consequently the distribution of [[biodiversity]] and levels of primary production in different ecosystems or biomes across the planet. Heat and temperature relate importantly to metabolic activity. [[Poikilotherms]], for example, have a body temperature that is largely regulated and dependent on the temperature of the external environment. In contrast, [[homeotherms]] regulate their internal body temperature by expending [[food energy|metabolic energy]].<ref name="Allee49"/><ref name="Ricklefs96"/><ref name="Kormondy95"/>

There is a relationship between light, primary production, and ecological [[energy budget]]s. Sunlight is the primary input of energy into the planet's ecosystems. Light is composed of [[electromagnetic energy]] of different [[wavelength]]s. [[Radiant energy]] from the sun generates heat, provides photons of light measured as active energy in the chemical reactions of life, and also acts as a catalyst for [[genetic mutation]].<ref name="Allee49"/><ref name="Ricklefs96"/><ref name="Kormondy95"/> Plants, algae, and some bacteria absorb light and assimilate the energy through [[photosynthesis]]. Organisms capable of assimilating energy by photosynthesis or through inorganic fixation of [[hydrogen sulfide|H<sub>2</sub>S]] are [[autotrophs]]. Autotrophs—responsible for primary production—assimilate light energy which becomes metabolically stored as [[potential energy]] in the form of biochemical [[Enthalpy|enthalpic]] bonds.<ref name="Allee49"/><ref name="Ricklefs96"/><ref name="Kormondy95"/>