Poikilotermisia

Poikilotermisia refers to the characteristic of an organism whose internal temperature varies considerably. This variation is typically a consequence of the organism's dependence on external heat sources to regulate its body temperature. Organisms exhibiting poikilothermy are often called ectotherms or cold-blooded, although these terms are not perfectly synonymous. Poikilothermy is a strategy found across a wide range of animal groups, including fish, amphibians, reptiles, and invertebrates.

In contrast to homeotherms, which maintain a stable internal temperature regardless of environmental fluctuations, poikilotherms experience body temperatures that closely track the ambient temperature. When their surroundings are warm, their body temperature rises, and when their surroundings are cool, their body temperature drops. This dependence on external heat means that their metabolic rate, activity levels, and physiological processes are directly influenced by environmental temperature. For example, a lizard basking in the sun will be more active than one in the shade or during cooler periods.

The ability to survive as a poikilotherm is often linked to specific adaptations. These can include behavioral strategies such as seeking out sunny spots for warmth or retreating to cooler burrows to avoid overheating. Physiological adaptations might involve tolerance to a wider range of body temperatures or the ability to slow down metabolic processes during cold periods. While poikilothermy can be advantageous in terms of energy conservation, as it requires less energy to maintain body temperature compared to homeothermy, it can also limit the range of environments an organism can inhabit and its activity periods.