Diversity, Classification and Plant Kingdom
Scope and taxonomic frame
This domain covers the diversity of living organisms, the rules of classification, and the major plant groups. The exam tests hierarchy, binomial nomenclature, kingdom criteria, and the diagnostic features and examples of algae, bryophytes, pteridophytes, gymnosperms and angiosperms.
Core rules
- Taxonomic hierarchy runs Kingdom → Division → Class → Order → Family → Genus → Species; species is the basic unit.
- Binomials are Latinised and italicised: genus capitalised, species lower case; author citation follows, as in Mangifera indica L.
- ICN rules use type specimens, priority and effective publication; common names are not stable.
- Five-kingdom classification separates Monera, Protista, Fungi, Plantae and Animalia by cell type, cell wall, nutrition and body organisation.
- Algae are thalloid and photosynthetic; Chlorophyceae store starch, Phaeophyceae laminarin, Rhodophyceae floridean starch.
- Bryophytes are amphibious, gametophyte-dominant, with protonema and no true vascular tissue.
- Pteridophytes are the first vascular plants; the gametophyte is a prothallus and spores are borne in sori.
- Gymnosperms have naked ovules and no fruit; angiosperms have flowers, enclosed seeds and double fertilisation.
Worked example
A specimen has a thallus, archegonia, no vascular tissue and a dominant gametophyte. Reasoning: thallus plus archegonia excludes vascular plants; dominant gametophyte and absence of xylem and phloem place it in Bryophyta, not Pteridophyta. If a protonema is also present, the identification is strengthened.
Traps
Do not call all algae green; do not treat bryophytes as vascular; do not place Pinus in angiosperms merely because it has seeds; do not confuse division with the zoological phylum; italics and author citation are mark-scoring details.