Diversity of Living Organisms
Domain 1 examines taxonomy and classification and the diversity of major plant and animal groups. The exam expects precise use of binomial nomenclature, taxonomic hierarchy and the diagnostic features that separate kingdoms, plant divisions and animal phyla.
Core rules
- Binomial names are italicised or underlined: genus starts with a capital, species epithet is lower-case. After first full mention, the genus may be abbreviated, e.g. M. indica.
- Hierarchy: Domain, Kingdom, Phylum or Division, Class, Order, Family, Genus, Species. Division is the plant equivalent of phylum.
- Whittaker’s five kingdoms are Monera, Protista, Fungi, Plantae and Animalia. Viruses are acellular and are not included; lichens are symbiotic associations of algae and fungi.
- Plant diversity runs from algae and bryophytes through pteridophytes and gymnosperms to angiosperms. Animal phyla are separated by symmetry, body plan, coelom, segmentation and larval features.
- Classification should reflect evolutionary relationships and use morphology, anatomy, biochemistry and molecular data.
Worked example
Place Mangifera indica in the hierarchy. Kingdom Plantae; Division Magnoliophyta; Class Dicotyledonae; Order Sapindales; Family Anacardiaceae; Genus Mangifera; Species indica. Reasoning: mango is a flowering dicot, so it belongs to angiosperms; its fruit and leaf morphology place it in Anacardiaceae. The species epithet indica is lower-case and the full binomial is italicised.
Traps
- Capitalising the species epithet, or writing both words with capitals.
- Using phylum for a plant instead of division.
- Placing viruses in Monera; they lack cellular organisation.
- Calling a lichen a single plant; it is a symbiosis.
- Confusing bryophytes (no vascular tissue) with pteridophytes (vascular, no seeds).