A poikilotherm is an organism whose internal temperatur varies considerably. It is the opposite o a homeotherm, an organism which maintains thermal homeostasis. Uisually the variation is a consequence o variation in the ambient environmental temperatur. Mony terrestrial ectotherms are poikilothermic. However some ectotherms remain in temperatur-constant environments tae the pynt that they are actually able tae maintain a constant internal temperatur (i.e. are homeothermic). It is this distinction that eften maks the term "poikilotherm" mair uisefu than the vernacular "cauld-bluidit", which is sometimes uised tae refer tae ectotherms mair generally.