what are poikiothermous and homoiothermous?

A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Usually the variation is a consequence of variation in the ambient environmental temperature. Many terrestrial ectotherms are poikilothermic.[1] However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature (ie are homeothermic). It is this distinction that often makes the term "poikilotherm" more useful than the vernacular "cold-blooded", which is sometimes used to refer to ectotherms more generally. Poikilothermic animals include types of vertebrate animals, specifically fish, amphibians, and reptiles, as well as a host of invertebrate animals.....

The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes. These are characteristics of mammals and birds.

Both the terms "warm-blooded" and "cold-blooded" have fallen out of favour with scientists because of the vagueness of the terms and an increased understanding of the field. Body temperature types are not discrete categories. Each term may be replaced with one or more variants, see the next section for examples. Body temperature maintenance (thermoregulation) incorporates a wide range of different techniques that result in a body temperature continuum.

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