SSC CGL Biology · Biodiversity and Classification
Plant Kingdom Classification
The four plant groups from mosses to flowering plants with an example of each, the classes of algae by colour, and a few protists SSC names.
Why this matters
Twelve questions in the bank: nine from the 2023 shifts and three from the 2024 shifts. Most give an example plant or alga and ask its group, so learn each group with two examples.
Concept 1 of 2: The four plant groups
Definition
The ladder:
- Bryophytes (mosses, liverworts): no vascular tissue; the gametophyte is the main plant. Marchantia, a liverwort, lifts its sex organs on umbrella-shaped stalks. Funaria, Polytrichum and Sphagnum are mosses.
- Pteridophytes (ferns, horsetails, lycophytes): the first vascular plants, with xylem and phloem but no seeds. Equisetum is the only living horsetail (Sphenopsida); Selaginella is a lycophyte.
- Gymnosperms (Cycas, Pinus): naked seeds in cones, no flowers; slow to reproduce.
- Angiosperms (rose): flowers, with seeds inside fruits.
In vascular plants the sporophyte is the main plant.
Carolus Linnaeus published Systema Naturae in 1735, with a sexual system for classifying plants.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Biodiversity and Classification · Plant Kingdom Classification
Cycas is not a fern
Concept 2 of 2: Algae by colour, and some protists
Definition
The classes:
- Chlorophyceae: green algae (Chlamydomonas, Spirogyra).
- Phaeophyceae: brown algae (Sargassum).
- Rhodophyceae: red algae, red from the pigment r-phycoerythrin.
- Cyanophyceae: blue-green algae, now called cyanobacteria.
Facts SSC uses:
- Spirogyra gametes are isogamous (alike) and non-flagellated; they fuse by conjugation. Chlamydomonas gametes have flagella.
- Gonyaulax is a dinoflagellate whose blooms cause red tides. Diatoms are chrysophytes; Euglena a euglenoid.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Biodiversity and Classification · Plant Kingdom Classification
A liverwort is not an alga
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Watch out for (2)
- Cycas is not a fern→ The four plant groups
- A liverwort is not an alga→ Algae by colour, and some protists
Test yourself on Biodiversity and Classification
15 past SSC CGL questions from this chapter, timed at 9 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.