Main Notes Column
Three Classes of Algae — Core Comparison
| Feature | Chlorophyceae | Phaeophyceae | Rhodophyceae |
|---|---|---|---|
| Common Name | Green algae | Brown algae | Red algae |
| Chlorophylls | a + b | a + c | a + d |
| Accessory Pigment | — | Fucoxanthin | Phycoerythrin |
| Storage Product | Starch | Laminarin | Floridean starch |
| Cell Wall | Cellulose | Cellulose + Algin | Cellulose |
| Habitat | Freshwater, some marine | Marine (cold) | Marine (deep) |
| Examples | Chlamydomonas, Spirogyra, Volvox, Chara | Sargassum, Laminaria, Ectocarpus, Fucus | Gelidium, Gracilaria, Polysiphonia, Porphyra |
Algae Diagram Reference:
Cue/Question Column
- Q: What are the three algal chlorophylls (second Chl of each class)? A: Green = b, Brown = c, Red = d (alphabetical: b < c < d)
- Q: Source of agar? A: Red algae — Gelidium and Gracilaria ONLY
- Q: What does algin come from? A: Brown algae cell walls (Laminaria, Sargassum)
Summary Box
Algae are classified by pigments (Chl types + accessory), storage products, and cell wall composition. Remember: Green-b-starch | Brown-c-fucoxanthin-laminarin | Red-d-phycoerythrin-floridean. Agar = RED algae; Algin = BROWN algae.