Ectotherm

An ectotherm (from Ancient Greek ἐκτός (ektós) 'outside' and θερμός (thermós) 'heat'), more commonly referred to as a "cold-blooded animal", is an animal in which internal physiological sources of heat, such as blood, are of relatively small or of quite negligible importance in controlling body temperature. Such organisms (frogs, for example) rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

Some of these animals live in environments where temperatures are practically constant, as is typical of regions of the abyssal ocean and hence can be regarded as homeothermic ectotherms. In contrast, in places where temperature varies so widely as to limit the physiological activities of other kinds of ectotherms, many species habitually seek out external sources of heat or shelter from heat; for example, many reptiles regulate their body temperature by basking in the sun, or seeking shade when necessary in addition to a host of other behavioral thermoregulation mechanisms.

In contrast to ectotherms, endotherms rely largely, even predominantly, on heat from internal metabolic processes, and mesotherms use an intermediate strategy.

Because there are more than two categories of temperature control utilized by animals, the terms warm-blooded and cold-blooded have been deprecated as scientific terms.

Adaptations

See also: Insect thermoregulation

Ectotherms, or cold-blooded animals, have special ways to help control their body temperature. For example, reptiles and many insects warm up by finding sunny spots and positioning themselves to get the most sunlight. When it gets too hot, they look for shade or cool water. In cold weather, honey bees stay warm by clustering together. Butterflies and moths can warm up by holding their wings in a way that catches the sun’s heat before they fly. Some caterpillars stay warm by grouping together.

Ectotherms also have body changes that help with temperature control. For instance, diving reptiles keep warm by letting cold blood near their skin pick up heat from warmer blood inside their bodies. Bullfrogs cool down by making extra mucus on their skin when it’s hot. During very cold times, some ectotherms go into a resting state called torpor, where their body processes slow down or even stop for a short time or much longer, depending on the animal. Reptile owners sometimes use special ultraviolet lights to help their pets warm up.

The article mentions a few specific animals and terms:

• forest tent caterpillar
• fall webworm
• endothermically
• poikilothermy
• homeothermy
• heat exchange
• torpor
• wood frog

Pros and cons

See also: Ambush predator

Ectotherms, often called cold-blooded animals, rely on external heat sources like sunlight to reach the right body temperature for their activities. Unlike warm-blooded animals, which produce their own heat using internal organs such as the liver or muscle, ectotherms depend on the environment to control their temperature. This means they often have lower energy needs and can survive with less food.

Because ectotherms need external heat, they are usually more active during the day when the sun is out. Some, like certain lizards, are nocturnal and use waiting strategies to catch prey without using much energy. This allows them to survive long periods without eating, unlike warm-blooded animals, which need regular meals to maintain their body heat.