User:BarredOwl.00/Ectotherm
From Wikipedia, the free encyclopedia
An ectotherm (from the Greek ἐκτός (ektós) "outside" and θερμός (thermós) "hot") is an organism in which internal physiological sources of heat are of relatively small importance in controlling body temperature.[1] Such organisms (for example, frogs) rely on environmental heat sources[2] which permit them to operate at optimal metabolic rates.[3]
Some ectotherms live in environments where temperatures are practically constant, such as regions of the abyssal zone of an ocean, and can be regarded as homeothermic ectotherms. However, in environments where temperature varies so widely as to limit physiological activities, many species habitually seek external sources of heat or, in contrast, shelter to cool down. For example, many reptiles regulate their body temperature by basking in the sun or seeking shade when necessary. In addition, most ectotherms regulate internal temperatures through behavioural thermoregulation mechanisms.
In contrast to ectotherms, endotherms rely largely, even predominantly, on heat from internal metabolic processes, and mesotherms use an intermediate strategy.
In ectotherms, fluctuating ambient temperatures may affect the body temperature. Such variation in body temperature is called poikilothermy, though the concept is not widely satisfactory, and the use of the term is declining. In small aquatic creatures such as Rotifera, the poikilothermy is practically absolute, but other creatures (like crabs) have wider physiological options at their disposal. These creatures can move to preferred temperatures to avoid ambient temperature changes or moderate their effects.[1][4] Some ectotherms have demonstrated sensitivities to temperatures during developmental stages, seen as variations to their growth rates and adult body size.[5][6] Ectotherms can also display the features of homeothermy, especially within aquatic organisms. Normally, their range of ambient environmental temperatures is relatively constant, and few attempt to maintain a higher internal temperature due to the high associated costs.[7]