The document discusses cladistics, which is a method of phylogenetic systematics used to classify organisms based on their evolutionary relationships. It uses cladograms to visually represent these relationships as branching diagrams of common ancestors. An example cladogram shows the evolutionary relationships between humans, cats, and other organisms. Outgroup comparisons help test different hypotheses about these relationships. Fossils can provide new evidence that changes our understanding of evolutionary history depicted in cladograms.
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