Taxonomy: Animals

There are animals so small you can’t see them … And there are whales as long as three buses. There are animals adapted to almost all environments of earth, on land and in water. Some live in the arctic cold, others in the hot desert. There are herbivores living in herds … … and there are lone predators. There’s a fantastic variation of animals and habitats in nature, and what is also fantastic is that all animals are related, closely or remotely.

Describing the relationships between animals, and classifying them into groups is called taxonomy. If you haven’t seen the introductory film about taxonomy, please watch it before you watch this one. When biologists began classifying animals, they started with the properties they could see. Tigers, lions, and leopards appeared to have many traits in common, both in appearance and in behaviour; and these three species were placed in the cat family. In the same way, all known animal species were classified using characteristics that could be observed.

But with greater knowledge about evolution, the study of how new species evolve from earlier species, knowledge grew about how different animal species are related. Biologists now wanted to create a family tree of all animal species, which could describe how species had developed during evolution. In certain cases, the previous classifications were correct. Tigers, lions, and leopards are closely related. But they also made other more surprising discoveries.

What do you think are birds’ closest relatives? They are in fact, dinosaurs. When the dinosaurs died out, about 65 million years ago, a small number of individuals survived, and from them all bird life evolved. This also means that all birds are much more closely related to reptiles like crocodiles and turtles, than you might think when you see them. Other animals that you might want to group together are fish and whales.

They swim in the same waters, and they look somewhat similar with their fins and streamlined bodies. But whales and fish are very remotely related. Whales are mammals. They breathe air and suckle their young, so they are more closely related to dogs or humans, than to fish, despite their similarities on the outside. At some point, during evolution, life found its way to land.

While fish evolved in the sea, mammals evolved on land. Some mammals found their way back to the ocean and adapted to a life in water. They slowly evolved into whales. And all these evolutionary lines are reflected in how biologists construct the taxonomy of the animal kingdom. The family tree of the animals on earth has eight basic levels.

At the very end of each branch, there is the species, for instance a wolf. The wolf belongs to the genus Canis, where we also find relatives like jackals. The genus Canis belongs to the family of Canidae, just like foxes and domesticated dogs. And then the groups become larger and larger closer to the stem of the tree. The family Canidae belongs to the order Carnivora, the class Mammalia and the phylum Chordata.

And at the bottom, we find the domain Eukaryotes, since all animals are built up of eucaryotic cells. That’s how taxonomy works. The whole animal kingdom, about one and a half million animal species, placed in a large tree which describes their evolutionary lines. And there you are too. Human beings.

At the end of the branch of the great apes.