Ektotermilised

Ektotermilised is a term used in biology to describe organisms whose body temperature is determined largely by external environmental conditions rather than by metabolic heat produced internally. In ectothermy, metabolic heat production is minimal or absent, so body temperature tends to reflect the surrounding environment. As a result, activity, growth and reproduction are strongly influenced by ambient temperature and microhabitat conditions.

Organisms that are ektotermilised rely primarily on behavioral strategies to regulate their temperature. They may bask in the sun to raise body temperature or seek shade, burrow or retreat to cooler microhabitats to avoid overheating. Their performance generally increases with temperature up to a species-specific optimum and declines outside that range. Some species also tolerate certain temperature extremes, but they do not maintain a constant internal heat level.

The term covers a wide taxonomic range. It includes most reptiles (such as snakes, lizards, turtles and crocodilians), amphibians (frogs and salamanders), many fishes, and numerous invertebrates (including many insects, mollusks and arthropods). The degree of dependence on external heat varies among lineages and even among individuals within a species.

Ecologically and evolutionarily, ektotermilised are adapted to environments where external heat is available and reliable enough to support life processes. Climate and seasonal changes strongly affect their distribution, activity patterns, growth rates, and reproductive timing. Climate change can alter the thermal landscapes these organisms rely on, with potential impacts on survival and ecosystem dynamics.

Etymology and related terms: the concept contrasts with endotermilised (endothermic) organisms, which generate substantial metabolic heat to regulate body temperature. Ektotermilised are often described as poikilothermic, though terminology varies across disciplines.