Mammals, one of which we humans are, appeared on Earth relatively recently. So, reptiles without competitors have ruled the ball on our planet for over a million centuries. When the first mammals appeared, the largest animals were dinosaurs.

The difference between reptiles and mammals

Reptiles and mammals are vertebrates. Reptiles are cold-blooded animals: the temperature of their blood changes depending on the ambient temperature. Mammals are warm-blooded animals: their internal temperature is maintained at a constant level, regardless of the temperature of the surrounding air. Perhaps some dinosaurs were warm-blooded, but no one knows for sure. What makes mammals different?

Their main difference from other animals is expressed in the name of the class. Mammals are animals whose females feed offspring with breast milk. The systematic Latin name for our class is Mammalia, from the Latin word mamma, which means “breast”. Reptiles of their cubs do not feed.

Animals that can be attributed to mammals and reptiles

Animals, which can be attributed to both mammals and reptiles, have existed for millions of years. Among them there is an interesting animal therapsida - this is a reptile, but its teeth are like that of a dog. This extinct animal, possibly had wool, maybe it was warm-blooded and laid eggs like a platypus.

There are other differences. Mammals are usually fully or partially covered with hair. Remember: dogs, cats, mice, gorillas are mammals, crocodiles, chameleons, rattlesnakes are reptiles. Mammals give birth to live cubs, and do not lay eggs. There is, however, one exception.

In Tasmania and Australia, the platypus lives - this is an animal with webbed feet and covered with wool, but ovipositing. Despite this, it is considered a mammal. The platypus can illustrate how the first mammals appeared. The platypus is covered with wool, but lays eggs, that is, combines the features of a mammal and a reptile. Scientists believe that before the appearance of true mammals, there were intermediate species - no longer reptiles, but also not mammals.

The emergence of true mammals

True mammals appeared 216 million years ago. According to scientists, they looked like small shrews. They ate insects and plants, and spent nights on trees. Wool and other hallmarks of mammals have evolved over millions of years. Evolution works by the method of natural variability and natural selection. Animals born with wool could have the same offspring.

Wool has become a good element of the device, as an appendage of the skin, which helps to better keep warm and, which is especially important for warm-blooded animals, to maintain a constant body temperature in a cold climate. Animals with wool could search for food in both cold and warm places, that is, they survived everywhere, and animals that did not have wool could live only in warm places.

Finally, the animals that appeared acquired all the necessary traits and “adaptations” of mammals. After the extinction of the dinosaurs, mammals took a dominant position in the animal kingdom and spread throughout the planet. Over millions of years, they have given many families - from cats to whales.