Classifying by evolutionary relationships
Phylogenetic classification arranges species into groups according to their evolutionary origins and relationships.
The system is hierarchical: smaller groups are contained within larger groups, without groups overlapping. Each classification group is a taxon; more than one are called taxa.
- Comparisons of DNA, RNA and proteins can provide evidence about evolutionary relationships.
- Greater molecular similarity usually indicates that organisms share a more recent common ancestor.
- Classification may change when new molecular evidence alters scientists' understanding of relationships.
Why classification is useful
Grouping organisms systematically gives scientists a common way to identify and discuss species and their relationships.
- Knowledge about one organism may help scientists make predictions about closely related species.
- Identifying and counting species can provide useful information for conservation.
- Additional molecular analysis can improve the accuracy of classifications over time.
Exam Tip: You do not need to recall the details of the three-domain or five-kingdom systems. Focus on how phylogenetic classification reflects evolutionary relationships.