Includes bibliographical references and indexes.

1. Systems and classifications. 1.1. Systematics and taxonomy. 1.2. Classification versus system. 1.3. Biological classifications from Andrea Cesalpino to the New Systematics. 1.4. Evolutionary systematics. 1.5. Numerical taxonomy. 1.6. Hennig’s phylogenetic systematics. 1.7. Contrasting systematic schools. 1.8. Towards a natural system of living organisms -- 2. Some steps in comparative biology. 2.1. Characters as ‘symptoms’ for recognizing taxa. 2.2. Characters for choice. 2.3. Homology. 2.4. Homoplasy. 2.5. Character coding. 2.6. Monophyly, paraphyly, polyphyly. 2.7. Determining character polarity. 2.8. Cladograms and trees. 2.9. Numerical methods for the reconstruction of phylogeny. 2.10. Ancestors. 2.11. Fossils and cladistic analysis. 2.12. Grouping and ranking. 2.13. Phylogeny versus adaptation -- 3. Biochemical and molecular systematics. 3.1. Micromolecules. 3.2. Macromolecules -- 4. The species. 4.1. Species concepts. 4.2. Taxonomic diversity within the specie