The scientific classification of polar bears looks like this:

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Ursidae

Genus: Ursus

Species: U. maritimus

To determine the biological classification like the one above, taxonomist look at morphological differences between organisms. Phylogeny (discussed in the next section) also looks at molecular sequences to establish links between groups.

Photo credit: Daniel J. Cox @ NaturalExposures.com