Poikilotherm

Poikilotherm

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. However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature (i.e. 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.

Characteristics

Poikilotherms can be characterized by a body temperature that varies directly with environmental temperatures. A well-known example of this are reptiles, like snakes and lizards, or amphibians, like frogs. These animals often bask in the sun to increase their body temperature and activity level. Some fish living in cold water are also poikilothermic.

Advantages and Disadvantages

The main advantage of being poikilothermic is that you don't need to eat as much food. This is because you are not burning energy to keep your body temperature stable. On the other hand, these animals may be more susceptible to sudden changes in body temperature, and may become inactive during cold weather.

See also

• Ectotherm
• Endotherm
• Homeotherm
• Heterotherm
• Thermoregulation

References

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