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Enchanted Learning All About Sharks!

Geologic Time Chart

Shark Glossary

Cladistics is a method of classifying organisms by common ancestry, based on the branching of the evolutionary family tree. Organisms that share common ancestors (and therefore have similar features) are grouped into taxonomic groups called clades. Cladistics can also be used to predict properties of yet-to-be discovered organisms. Phylogenetic systematics is a method of classification based on the evolutionary history of organisms, dividing organisms into meaningful groups and subgroups. It was developed by Willi Hennig, an entomologist, in 1950, but was not well accepted until decades later.

Cladistics is based on three principles:

Groups of organisms are descended from a common ancestor. At each node (divergence of a population), there are two branching lines of descendants. Evolution results in modifications of characteristics over time.

A cladogram is a branching diagram that depicts species divergence from common ancestors. They show the distribution and origins of shared characteristics. Cladograms are testable hypotheses of phylogenetic relationships.

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