The seven taxa are levels of classification recognized by biologists for placing all living organisms in a unified system of taxonomy. Kingdom, phylum and class are the highest orders of classification, followed by order, family and genus. Species is the lowest common division among organisms.
At the highest commonly used level of taxa, organisms are divided into kingdoms. Plants, animals and fungi all exist within their own kingdoms. Phyla are similarly large groupings of organisms that, prior to the advent of modern genetics, were difficult to connect with each other in unified trees of descent. Chordata is the phylum that contains all vertebrates.
The next level down is class. Classes of organisms may be monophyletic if all members share a common ancestor, or polyphyletic if some members are more closely related to outgroups. Mammals are a monophyletic class, as are birds, but reptiles are polyphyletic, as some reptiles are more closely related to birds than to other reptiles.
Each class is divided into orders, families and genera. Primata is one order of mammals, as is chiroptera, which is home to all bats. Families tend to be closely related groups. Among primates, the family Hominidae contains the great apes. A genus is a group of very close species. Homo is a genus within Hominidae, and sapiens is the sole remaining species of human.