Külmaverelised

Külmaverelised, also known as ectotherms, are animals that rely on external sources of heat to regulate their body temperature. This contrasts with warm-blooded animals, or endotherms, which generate their own internal heat. The term "cold-blooded" is somewhat misleading as the body temperature of an ectotherm can vary significantly depending on the environment, and can be quite warm when exposed to sufficient heat.

Ectotherms achieve thermoregulation through behavioral means. For instance, reptiles like lizards will bask in the sun to warm up and seek shade to cool down. Fish, which live in a relatively stable aquatic environment, often have body temperatures close to that of the surrounding water. Amphibians, which typically live in moist environments and have permeable skin, also rely heavily on behavioral thermoregulation. Insects and other invertebrates are also ectothermic, with their activity levels often dictated by ambient temperatures.

The metabolic rate of ectotherms is generally lower than that of endotherms, meaning they require less food to sustain themselves. This can be a significant advantage in environments with limited food resources. However, their reliance on external heat sources can limit their activity in cold conditions, making them more vulnerable to temperature fluctuations and the onset of winter. This is why many ectotherms hibernate or enter a state of dormancy during colder months.