What are the differences between a cold blooded animal and a warm blooded animal?


In animals, we often hear about hot blood or cold blood according to the races. Any neophyte thinks that this difference comes from the temperature of the blood, which can be one or the other. It is not, and the real difference between cold blood and warm blood is more complex than it seems at first glance. Many species of animals do not have blood, for example jellyfish or sea sponges. In fact, it’s all about the change in body temperature.

The misconception about the temperature of the blood of animals

When we talk about the temperature of a so-called cold-blooded or warm-blooded animal, we immediately think of the blood temperature. This term is incorrect because many species of animals do not have blood in their bodies and yet they are alive and are part of the animal rule. In reality, it is about change in body temperature some change. You should know that some so-called cold-blooded animals have an internal temperature that can easily reach 45 °. The so-called warm-blooded animals can, conversely, lower their temperature below 30 ° and much more. Species whose temperature can be variable or fixed are homeothermic animals and the others, ectothermic animals.

Ectothermal or poikilothermic animals

The so-called cold-blooded animals are in fact ectotherms also named poikilotherms. In fact, these animals have a variable internal temperature. They do not produce their internal heat, but adjust it according to the environment in which they operate. For example, when night falls, their temperature drops and during the day, especially if it is sunny, their temperature rises. Some of these animals can only live when it is hot, because when the temperature of the atmosphere goes down, they die. This is the case with a multitude of insects, such as, for example, dragonflies.

The various strategies used by ectothermic animals to increase their temperature

To increase their temperature, ectothermic animals said cold blood, use several strategies to increase the their internal body temperature. In principle, they change the environment. Thus, some will be heated in the sun like the lizard or the snakes. Others will bury themselves in the sand or the earth. Still others will travel thousands of kilometers to swim in warmer waters or for their physical activity. These changes are quite delicate for some. In ovoviviparous people keeping their eggs in their body like female snakes who must constantly warm themselves without excessively, but without cooling down so that their body temperature does not vary too much at this period of their life.

Warm-blooded homeothermic animals

The homeothermic animals say to hot blood are among the species whose internal temperature can vary. They have the ability to thermogenesis which is the ability to generate heat. No matter what the temperature is outside, their internal temperature remains about the same. These warm-blooded animals, or more exactly homeothermic animals, spend a lot of energy to regulate this internal temperature and feed much more often than ectothermic animals. The human was part of this category. Its temperature is around 37 ° day and night and whatever the season or weather conditions. The internal temperature may rise if there is disease. In this case, when the temperature rises, it is called fever. This increase is a warning and the fever helps fight the pathology. From homeothermic animals, we find birds and mammals.

From homeothermic animals say to hot blood, there is an exception in homeothermic animals. Those are the heterothermal animals who have the ability to hibernate like bears for example. In winter, when it is cold, they manage to lower their body temperature to spend a minimum of energy by sleeping in the coldest season. This ability serves them to resist famine during this time. Some birds are also homeothermic like the swift when it can no longer feed its hunger. During a whole night in winter, he is able to fall into lethargy to conserve his energy.

The origin of warm-blooded homeothermic animals

Since the early 1990s, it is now known that many dinosaurs and birds were and are homeothermic. In 2017; It was carried out isotopic analyzes by researchers on 90 fossils. This analysis demonstrated that thehomeothermy appeared during the Upper Permian, 252 to 259 million years ago. Thanks to this homeothermy, they could have survived during the extinction of the Permian-Triassic, 22 million years ago.

Some specificities

Some animals do not fit into any of the above categories. They appeal to a thermal regulation only partial like sharks, tunas or swordfish which can regulate the temperature of their brain, heart and eyes when hunting in very cold water.

Other animals use the collective thermal regulation allowing them to warm together like bees by vibrating their wings to warm the hive in winter or cool it in summer.

Animals still use other strategies to warm or cool their internal temperature, and this, that they fall into the category of homeotherms or some ectotherms. Thus, snakes, lizards and other reptiles will expose themselves to the sun to increase their internal temperature which can easily go up to 45 °. Others will use a thick fat layer like walruses or very thick feathers like the penguin, but also regroup like the Emperor Penguin.

To warm up, a ectothermic animal still takes its size into account, because the smaller it is, the larger the body surface it has to expose. The same is true if he has to lower this temperature by taking refuge in the shade like certain insects in the desert.

These differences between ectothermic animals and the homeothermic animals all have one thing in common: that of maintaining a sufficient temperature in order to be able to survive in an environment adapted to each species.

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