How do scientists classify organisms?

Biologists have developed a specific system for classifying all living organisms which is based on dividing all known organisms into groups according to common features which scientists believe are biologically significant. This system, known as the Classification of Living Things, gradually isolates each living organism into the following groups: Kingdom, Phylum, Class, Order, Family, Genus, and Species.

The Classification of Living Things is a type of taxonomy. To use it, scientists match an organism to the proper subgroup starting at the top with Kingdom and working down to Species:

1. Kingdom - determined based on how a living organism obtains its food.
2. Phylum - divides organisms within a kingdom based on physical similarities which suggest a common ancestry.
3. Class - divides organisms with a phylum based on another, more significant similarity. For example, mammals drink milk from their mothers.
4. Order - divides organisms within a class based on a taxonomy key or a specific checklist of characteristics unique to each Order.
5. Family - divides organisms within a particular class into groups which share so many common characteristics that they are believed to be related to each other according to evolution.
6. Genus - an organism's generic name, which further isolates it from other members of its family. This is the first part of its two-part Latin name, or the "homo" in "homo sapiens."
7. Species - the strictest, lowest, and most specific level of classification. These organisms share so much similarity that they are able to mate and reproduce with each other. This is the second part of an organism's two-part Latin name, such as "sapiens."