Plant Kingdom: Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms
Domain 2: Plant Kingdom - what is tested
The exam tests the diagnostic features, representative genera and life-cycle pattern of algae, bryophytes, pteridophytes, gymnosperms and angiosperms, plus alternation of generations and economic uses.
Core rules
- Algae: chlorophyll-bearing, thalloid, mostly aquatic; examples Chlamydomonas, Spirogyra, Sargassum. Reserve food starch; cell wall cellulose.
- Bryophytes: amphibians of the plant kingdom; gametophyte is the dominant, independent green phase; sporophyte depends on it. Examples Marchantia, Funaria. Water is needed for sperm transfer.
- Pteridophytes: first vascular plants; sporophyte dominant with true roots, stem and leaves; gametophyte is a small prothallus. Examples Selaginella, Nephrolepis. Sori bear spores.
- Gymnosperms: naked seeds, no fruit; heterosporous; examples Pinus, Cycas, Ginkgo. Male and female cones; wind pollination common.
- Angiosperms: flowers and fruits; double fertilisation produces triploid endosperm; examples Oryza, Helianthus. Monocots and dicots differ in cotyledon number, venation and vascular bundles.
Worked example
In Funaria, the leafy green shoot is the gametophyte (n). Archegonia and antherozoids are produced on it; after fertilisation the zygote grows into a sporophyte (2n) consisting of foot, seta and capsule. The capsule makes spores by meiosis. Reasoning: the dominant photosynthetic phase is gametophytic, so bryophytes show a gametophyte-dominant life cycle; the sporophyte is nutritionally dependent.
Traps
Calling bryophytes vascular; saying pteridophytes have seeds; treating all algae as marine; saying gymnosperms lack seeds; mixing up dominant phase in bryophytes and pteridophytes; forgetting that angiosperm endosperm is triploid.