The animals poïkilothermes (or with “ cold blood ” or hétérothermes ) are animals having a body temperature which varies. By this characteristic, they differ from the Homéotherme S which control their internal temperature.
This not-control of their temperature interns prevents them from having a “normal” activity during the cold periods, but it is a characteristic much more energy saver who the Homéotherme S. the two types survived because they are characteristic of different lifestyles, even if it is considered that the Homéothermie is a advanced Caractère.
Classification
The animals with cold blood refer to 3 principal mechanisms of Thermorégulation.-
exothermy: the animals control the temperature of their body thanks to external means (to put itself at the sun, for example).
- poikilothermy: the temperature of these animals vary, often according to the room temperature of the immediate environment.
- bradymetabolism: the metabolism at rest is low (EP in the event of extreme winter conditions, or for lack of food); these animals can " sombrer" in states close to death, until the return of favorable conditions (as for the Hibernation).
Very few animals have only one of these 3 characteristics; the majority use a combination of these 3 aspects of thermophysiology (with their counterparts: endothermy, homeothermy and tachymetabolism), to cover a broad spectrum of all the types of body temperatures.
Strategy
Various strategies of control of temperature include:- the Snakes and the Lizard S, benefitting from the sun on rocks
- the Poisson, changing depth according to the temperature of water
- animals of the desert, tie profit of sand during the day
- the Insects, heating the muscles of their wings by producing vibrations
Often, the poikilothermes have a metabolism more complex than the homéothermes. For an important chemical reaction, they can indeed have systems from 4 to 10 Enzymes, which operate at various levels of temperatures. Consequently, the poikilothermes often have Génome S more complex than their counterparts homéothermes in same a ecological Niche. An good example is the Grenouille, as well as the Crapaud.
Consequences
- Because of their variable metabolism, the poïkilothermes are not very adapted for the complex systems, or with great energy requirements, like the brains.
- Certain large poïkilothermes, thanks to a report/ratio volume/surface of favorable skin , is able to maintain a temperature of body relatively high and a high metabolism. This phenomenon, called Gigantothermie, was observed on the turtles, and was present at the majority of the dinosaurs and old reptiles of the seas.
- the anaerobic metabolism of Poïkilothermes reptiliens, which practically functions without muscular oxygen, allows, equal volume, to have a muscular power 2 to 3 times superior with that of the Homéotherme. N the other hand, the endurance of Poïkilothermes is less than that of the Homéotherme S.
Between blood-heat and coolness
Our knowledge improving, of the animals previously “catalogued” with cold blood (like tuna or the swordfish) was displaced because they also have characteristics of warm-blooded animals. They are thus in an intermediate category (see ad hoc paragraph in the article on the Homéotherme S).
See too
Internal bond
External bond
- The Reptipage: What is cold-blooded?
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