The source of energy that animals use is the basis on which animals are divided into two groups, namely cold-blooded and warm-blooded animals. Cold-blooded animals are also known as ectothermic or poikilothermic animals. Their bodies cannot regulate temperatures internally, so their temperature is not constant and varies according to their environment. In hot environments, their blood can get much warmer than that of warm-blooded animals in the same area. To regulate their temperature, cold-blooded animals bask perpendicular to sun rays to get warm, and when they want to cool down they lie parallel to the sun, or keep their mouths open or seek shade.
Cold-blooded animals can be either terrestrial or aquatic. All reptiles, including snakes, lizards, turtles, tortoises, alligators, and crocodiles, some insects such as the busy dragonflies and bees, amphibians such as frogs, toads, and salamanders, as well as fish, including sharks, are all cold-blooded animals. Though dinosaurs were reptiles, they are believed to have characteristics of both cold and warm blooded animals, and belonged to a transitional group with a complex metabolism, similar to what is seen in modern birds.
Cold-Blooded Animal Characteristics
In warm temperatures, cold-blooded animals are more active and can travel more quickly. This occurs because heat activated reactions provide energy to move muscles. In the absence of heat the animal becomes slow and sluggish. So they are usually inactive and rest when it is cold. As they do not need to feed much, they spend less time looking for food, so this life strategy works for them. In places such as deserts where food is scarce, lizardsand other cold-blooded animals have an advantage. Most of the cold-blooded animals hibernate many months to tide over the cold winter, or have a short life span so they die as in the case of many insects. Honey bees hurdle together and flap their wings to stay warm. Many fishes will move to deeper and warmer waters, while insects move underground or to warmers areas to avoid the winter cold. Some fish species have a special protein in their blood with anti-freeze properties. To avoid extended periods of warm temperatures during the day many cold-blooded animals sleep in cool or shady places. This is aestivation or summer sleep, and differs from hibernation in that it lasts only for a day. Snails, frogs, salamanders, earthworms, snakes, crocodiles, desert tortoises are all known to aestivate.
Benefits Of Ectothermy
Since they do not generate their own warmth, the ratio of body weight to surface area is not as important as in warm-blooded animals. Therefore, cold-blooded animals can be either small, as in insects and lizards, or large, such as with crocodiles. They are also free from parasites as their body temperatures is not constant, so they suffer less from illness than warm blooded animals. Since they do not need food to generate heat, they can survive without feeding for extended periods, which is why some snakes feed only once in a month. In times of scarcity, the cold-blooded animals rest, remain inactive and cool. Most of the food they do eat gets converted to body mass.
Disadvantages Of Ectothermy
Cold blooded animals are generally found confined to warmer regions of the world. When the temperature drops, their metabolism slows down. If the temperatures remain cold for extended periods, cold-blooded animals can die.