| Cold-blooded |
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Since that time, advances in the study of how creatures maintain their internal temperatures (deemed: thermophysiology), have shown that many of the earlier notions of what ). Today scientists realize that body temperature types are not a simple matter of black and white. Most creatures fit more in line with a graded spectrum from one extreme (cold-blooded) to another ( Warm-blooded ). BREAKING DOWN COLD-BLOODEDNESS Cold-bloodedness generally refers to three separate areas of Thermoregulation . # Ectothermy # Poikilothermy # Bradymetabolism
Few creatures actually fit all three of the above criteria. Most animals use a combination of these three aspects of thermophysiology, along with their counterparts ( Endothermy , Homeothermy & Tachymetabolism ) to create a broad spectrum of body temperature types. Most of the time, creatures that use any one of the previously defined aspects, are usually pigeon-holed into the term ''cold-blooded''. Physiologists also coined the term '' Heterothermy '' for creatures that exhibit a unique case of poikilothermy. TYPES OF TEMPERATURE CONTROL Examples of this temperature control include:
Many Homeothermic , or warm-blooded, animals also make use of these techniques at times. For example, all animals are at risk of overheating on hot days in the Desert Sun , and most homeothermic animals can shiver. Poikilotherms often have more complex metabolisms than homeotherms. For an important chemical reaction, poikilotherms may have four to ten Enzyme systems that operate at different temperatures. As a result, poikilotherms often have larger, more complex Genome s than homeotherms in the same Ecological Niche . Frog s are a notable example of this effect. Because their metabolism is so variable, poikilothermic animals do not easily support complex, high-energy organ systems such as brains or wings. Some of the most complex adaptations known involve poikilotherms with such organ systems. One example is the swimming muscles of Tuna , which are warmed by a Heat Exchanger . In general, poikilothermic animals do not use their Metabolism s to heat or cool themselves. For the same body weight poikilotherms need 1/3 to 1/10 of the energy of homeotherms. They therefore eat only 1/3 to 1/10 of the food needed by homeothermic animals. Some larger poikilotherms, by virtue of their substantial Volume to Surface Area ratio, are able to maintain relatively high body temperatures and high Metabolic rates. This phenomenon, known as Gigantothermy , has been observed in Sea Turtle s and Great White Shark s, and was most likely present in many Dinosaurs and ancient sea reptiles (such as Ichthyosaurs and Plesiosaurs ). ECOLOGICAL NICHES It is comparatively easy for a poikilotherm to accumulate enough energy to reproduce. Poikilotherms in the same ecological niche often have much shorter generations than homeotherms: weeks rather than years. This energy difference also means that a given niche of a given ecology can support three to ten times the number of poikilothermic animals as homeothermic animals. However, in a given niche, homeotherms often drive poikilothermic competitors to extinction because homeotherms can gather food for a greater fraction of each day. Poikilotherms succeed in some niches, such as islands, or distinct Bioregion s (such as the small bioregions of the Amazon Basin ). These often do not have enough food to support a viable breeding population of homeothermic animals. In these niches, poikilotherms such as large lizards, crabs and frogs supplant homeotherms such as birds and mammals. SEE ALSO
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