| General Characteristics of Algae |
| Common Name |
Algae |
| Habitat |
Aquatic (freshwater and marine), moist stones, soils, wood, in association with fungi (lichen), on animals (e.g., sloth bear) |
| Plant Kingdom |
Chlorophyll-bearing, simple, thalloid, autotrophic organisms |
| Form and Size |
Highly variable, from colonial forms (Volvox) to filamentous forms (Ulothrix, Spirogyra), massive plant bodies (kelps) |
| Vegetative Reproduction |
By fragmentation, each fragment develops into a thallus |
| Asexual Reproduction |
By production of spores, most common being zoospores (flagellated, motile), germinate to form new plants |
| Sexual Reproduction |
By fusion of gametes, can be isogamous, anisogamous, or oogamous |
| Isogamous Reproduction |
Fusion of similar gametes, flagellated (e.g., Ulothrix) or non-flagellated (e.g., Spirogyra) |
| Anisogamous Reproduction |
Fusion of dissimilar gametes, e.g., Eudorina |
| Oogamous Reproduction |
Fusion of one large non-motile female gamete and a smaller motile male gamete, e.g., Volvox, Fucus |
| Economic Importance |
Significant for CO2 fixation, primary producers of energy-rich compounds, food sources (e.g., Porphyra, Laminaria, Sargassum), hydrocolloids (e.g., algin, carrageen), agar production, protein-rich food supplements (e.g., Chlorella) |
| Ecological Importance |
Increase dissolved oxygen through photosynthesis, basis of aquatic food cycles |
| Divisions |
Chlorophyceae, Phaeophyceae, Rhodophyceae |
| Chlorophyceae (Green Algae) |
| Common Name |
Green algae |
| Plant Body |
Unicellular, colonial, or filamentous; grass green due to chlorophyll a and b |
| Chloroplasts |
Discoid, plate-like, reticulate, cup-shaped, spiral, or ribbon-shaped |
| Storage Bodies |
Pyrenoids (protein and starch) |
| Cell Wall |
Rigid, inner layer of cellulose, outer layer of pectose |
| Reproduction |
Vegetative (fragmentation), asexual (flagellated zoospores), sexual (isogamous, anisogamous, oogamous) |
| Examples |
Chlamydomonas, Volvox, Ulothrix, Spirogyra, Chara |
| Major Pigments |
Chlorophyll a, b |
| Stored Food |
Starch |
| Flagellar Number and Position |
2-8, equal, apical |
| Habitat |
Freshwater, brackish water, salt water |
| Phaeophyceae (Brown Algae) |
| Common Name |
Brown algae |
| Habitat |
Primarily marine |
| Plant Body |
Simple branched forms (Ectocarpus) to profusely branched kelps (up to 100 meters); usually attached to substratum by a holdfast, with a stalk (stipe) and leaf-like photosynthetic organ (frond) |
| Pigments |
Chlorophyll a, c, carotenoids, xanthophylls (fucoxanthin) |
| Colour |
Olive green to brown |
| Storage Food |
Laminarin, mannitol |
| Cell Wall |
Cellulosic, covered with gelatinous coating of algin |
| Vegetative Reproduction |
By fragmentation |
| Asexual Reproduction |
By biflagellate zoospores, pear-shaped with two unequal laterally attached flagella |
| Sexual Reproduction |
May be isogamous, anisogamous, or oogamous; union of gametes can occur in water or within the oogonium (oogamous species); gametes are pyriform with two laterally attached flagella |
| Examples |
Ectocarpus, Dictyota, Laminaria, Sargassum, Fucus |
| Major Pigments |
Chlorophyll a, c, fucoxanthin |
| Stored Food |
Mannitol, laminarin |
| Flagellar Number and Position |
2, unequal, lateral |
| Habitat |
Freshwater, brackish water, salt water |
| Rhodophyceae (Red Algae) |
| Common Name |
Red algae |
| Habitat |
Marine, found in warmer areas, at various depths |
| Plant Body |
Multicellular, some with complex body organisation |
| Pigments |
Chlorophyll a, d, phycoerythrin |
| Stored Food |
Floridean starch (similar to amylopectin and glycogen) |
| Cell Wall |
Cellulose, pectin, and poly sulfate esters |
| Reproduction |
Vegetative (fragmentation), asexual (non-motile spores), sexual (oogamous with complex post-fertilization developments) |
| Examples |
Polysiphonia, Porphyra, Gracilaria, Gelidium |
| Major Pigments |
Chlorophyll a, d, phycoerythrin |
| Stored Food |
Floridean starch |
| Flagellar Number and Position |
Absent |
| Habitat |
Freshwater (some), brackish water, salt water (most) |
