Cold-blooded organisms, more technically known as poikilothermic, are animals that have no internal metabolic mechanism for regulating their body temperatures. Some (usually smaller) animals have unregulated temperatures, but most have sophisticated physiological and behavioral techniques for obtaining their desired core body temeprature from the environment. Cold-blooded animals are often referred to as ectotherms. Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa ?Myxozoa Superphylum Deuterostomia    Chordata (vertebrates, etc. ...

Ectotherms depend largely on external sources of heat, such as solar radiation. As the environmental temperature increases, the animal's metabolic rate will increase. Lizards, fish, and amphibians are examples of ectotherms. Whereas an endotherm, or warm-blooded animal will use up to 98% of its energy for heat production, an ectotherm has all this energy available for activity, growth, repair and reproduction. Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. ... For other uses, see Amphibian (disambiguation). ... A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down...

Types of temperature control

Examples of this temperature control include:

• Snakes and lizards sunning themselves on rocks.
• Fish changing depths in the water column to find a suitable temperature.
• Desert animals burrowing beneath the sand during the day.
• Insects that warm their flight muscles by vibrating them in place.
• Dilating or constricting peripheral blood vessels to adapt more or less quickly to the ambient temperature.

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. Superfamilies and Families Henophidia Aniliidae Anomochilidae Boidae Bolyeriidae Cylindrophiidae Loxocemidae Pythonidae Tropidophiidae Uropeltidae Xenopeltidae Typhlopoidea Anomalepididae Leptotyphlopidae Typhlopidae Xenophidia Acrochordidae Atractaspididae Colubridae Elapidae Hydrophiidae Viperidae Snakes are cold blooded legless reptiles closely related to lizards, which share the order Squamata. ... This page is about Lizards, the order of reptile. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world. ... A dune in the Egyptian desert Desert in California In geography, a desert is a landscape form or region that receives little precipitation. ... Orders Subclass Apterygota Symphypleona - globular springtails Subclass Archaeognatha (jumping bristletails) Subclass Dicondylia Monura - extinct Thysanura (common bristletails) Subclass Pterygota Diaphanopteroidea - extinct Palaeodictyoptera - extinct Megasecoptera - extinct Archodonata - extinct Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Blattodea (cockroaches) Mantodea (mantids) Isoptera (termites) Zoraptera Grylloblattodea Dermaptera (earwigs) Plecoptera (stoneflies) Orthoptera (grasshoppers, crickets... The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down...

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 genomes than homeotherms in the same ecological niche. Frogs are a notable example of this effect. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... In ecology, a niche is a term describing the relational position of a species or population in an ecosystem. ... Frogs are amphibians in the Order Anura, which includes frogs and toads. ...

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 metabolisms 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. Species Thunnus alalunga Thunnus albacares Thunnus atlanticus Thunnus maccoyii Thunnus obesus Thunnus orientalis Thunnus thynnus Thunnus tonggol Tuna are several species of ocean-dwelling fish in the family Scombridae, mostly in the genus Thunnus. ... A heat exchanger is a device for transferring heat from one fluid to another, where the fluids are separated by a solid wall so that they never mix. ... Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος(metavallo), the Greek word for change), in the most general sense, is the ingestion and breakdown of complex compounds, coupled with the liberation of energy, and the consequent generation of waste...

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 bioregions (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. An ecoregion is a relatively large area of land or water that contains a geographically distinct assemblage of natural communities. ... Geography The South American rainforest of Amazonia (60% located in Brazil), the largest in the world, was originally covered by more than 7,000,000 km² (2 million square miles) of dense tropical forest. ...