 Principles of Systematics, Module 194, Warm-Blooded and Cold-Blooded Animals Warm-Blooded animals are those animals which have ability to regulate their body temperature. For example, mammals and birds. And those animals which do not have ability to regulate their body temperature are known as cold-blooded animals. We divide animals into two categories. Warm-Blooded animals and Cold-Blooded animals. Warm-Blooded animals are actually those animals which regulate their body temperature. They keep their body temperature constant. Cold-Blooded animals were used for such animals which do not have the ability to regulate their body temperature. Now, if we talk about Warm-Blooded animals, then birds and mammals are examples of Warm-Blooded animals. Similarly, frog, fishes, invertebrates are examples of Cold-Blooded animals. If we talk about humans, then humans keep their body temperature fixed. For example, our body temperature is 37. Now, if the external environment of our body changes, for example, the external environment outside is 40 degrees, but our internal body temperature remains 37. There is a mechanism in our body that the extra heat comes into our body as a result of metabolic reactions. It removes our body temperature so that the temperature of the body is regulated. Similarly, if our external environment has a lower temperature, for example, it is 20 degrees, then there is a system in our body that keeps our body's heat maintained. In our body, these kinds of mechanisms start, like shivering can start, or metabolic heat is present in the body and keeps the body's temperature maintained. Whereas Cold-Blooded animals do not have the ability to regulate their temperature. Now, in the examples of Warm-Blooded animals, we talked about birds and mammals. These animals can regulate their body temperature. They can easily survive in different types of habitats. Because in different habitats, different environmental conditions, if the temperature is different, then they have the ability to regulate their body temperature. That is why their range of dispersion is quite large. Whereas Cold-Blooded animals have the ability to regulate their body temperature, therefore their dispersion range is limited. They live in specific areas. This classification has been used for a long time. But later, on this classification, a lot of people took the liberty. Because a lot of animals are like this, because they are in Warm-Blooded animals, but they do not regulate their body temperature. For example, if we talk about hummingbirds, the body temperature of hummingbirds, for example, when they are not active during the night, then they drop their body temperature. Their metabolic activity decreases. This is a specific phenomenon that hummingbirds follow. It is called Daily Torpor. Similarly, there are a lot of Cold-Blooded animals who regulate their body temperature, which is constant. For example, a lot of fish species live under the water, where the temperature does not fluctuate much. On this basis, their body temperature remains constant. For example, the species of lizards talk about lizards when their body temperature decreases, they absorb external heat and maintain their body temperature. In this classification, because there were a lot of problems, this classification system was rejected and a new classification system was introduced. The basic difference between Warm-Blooded and Cold-Blooded animals is that they can regulate their body temperature while Cold-Blooded animals cannot regulate their body temperature. The dispersion range of Warm-Blooded animals is quite large. They can easily survive in various environmental conditions, but the range of Cold-Blooded animals is quite narrow. They are limited, they are restricted in specific areas and they spend their lives on them.