Chemotaxonomy:
Three kinds of compounds:
- Primary metabolites: those necessary for vital functions, e.g. citric acid used in Krebs cycle
- Secondary metabolites: perform non-vital functions
- alkaloids, phenolics, glucosinalates, amino acids, terpenoids
- usually pigments, poisons, scents, waste substances, etc.
- Semantides: information carrying molecules
Most taxonomic data comes for secondary metabolites and semantides