Class (biology)

In biological taxonomy, a class is a way scientists group living things that are related to each other. The word "class" comes from the Latin word classis. In the big family tree of life, classes sit between bigger groups called phyla and smaller groups called orders.

Classes help us organize the many different kinds of plants, animals, and other organisms. For example, all mammals—like humans, whales, and bats—belong to the same class, called Mammalia. This tells us they share important features, such as giving birth to live babies and having hair or fur.

Other well-known ranks, or levels, in this grouping system include domain, kingdom, phylum, order, family, genus, and species. Understanding classes helps scientists and students study and talk about living things in an organized way.

History

The idea of a "class" in biology began with a French botanist named Joseph Pitton de Tournefort in 1694. He was the first to give this group of living things its own special name, instead of just calling it a top-level group.

Later, Carl Linnaeus, a famous scientist, also used classes to organize animals, plants, and minerals in his work called Systema Naturae from 1735. Today, we still use classes for animals, but for plants, scientists often talk about groups called "clades" instead. The class used to be the top level of grouping, but then scientists like George Cuvier and Ernst Haeckel introduced a new level called "phyla."