Derived characters are features in organisms that have been modified for specific functions as a result of evolution. They are used in cladistic analysis, which is a method of classifying organisms according to certain physical characteristics or behavioral traits that have appeared through the evolutionary process.
Derived characters are those that are not present in an organism's evolutionary ancestors and are distinct from primitive characters. While primitive characters establish broad classifications used for grouping in cladistic analysis, such as fur and mammary glands on mammals, derived characters are more unique and help to classify organisms into smaller groups. An example of a derived character in mammals is an appendage containing an opposable thumb. Another example is the presence of appendages in mammals that make aquatic movement possible, such as in whales or dolphins. The more derived characters organisms share, the closer they are related.
Once derived and primitive characters are known, a cladogram can be constructed to show the evolutionary link between groups of organisms. Experts use computer programs to enter these characteristics, and the information is used to quickly group organisms according to shared evolutionary structures.
The use of derived characters in cladistic analysis is just one of several alternatives to classifying organisms.