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Algae 2/3: 1. Unicelluar algae (various groups) 2. Green algae (Chlorophyta)
Unicellular algae
Euglena
Diatom
Dinoflagellate
Golden Algae
Unicellular algal groups • Cyanophyta (Blue-green Algae; prokaryotes) • Diatoms • Dinoflagellates • Chrysophyta • Chlorophyta (Green Algae) • Rhodophyta (Red Algae)
Occurrence of Unicellulars • Phytoplankton (freshwater, marine) • Benthic microalgae • Epiphytic (on other algae) or on rocks, sediments, etc. • Terrestrial algae (walls, trees, etc) • Symbioses: in lichens, root nodules, marine sponges • Parasites (e.g. heterotropic dinoflagellates) • Hot springs • Ice algae (‘red snow’)
How to distinguish between different unicellular algae? • Pigments? • Flagella: types of movement? • Type of reproduction (sexual, asexual)? • Life history? • Cell structure? • Formation of colonies or filaments?
Cyanobacteria (Cyanophyta) • = ‘Blue-green Algae’ • Prokaryotic, no cell organelles • Pigments: chlorophyll a, phycoerythrin + phycocyanin • Only asexual reproduction • Some can fix atmospheric Nitrogen • Can form blooms • In extreme habitats (e.g. hot springs) • In lichens
Cyanobacteria bloom
Terrestrial environments
Extreme halophytes
Hot springs
Figure 28.3 Euglena: an example of a singleŠcelled protist
Spirogyra Conjugation
Diatoms
Figure 28.17 Diatoms: Diatom diversity (left), Pinnularia (left)
Figure 28.17x Diatom shell
Diatom Characteristics • 2 orders: • Centrales: radial symmetry (centric diatoms) • Pennales: bilateral symmetry (pennate diatoms) • Cell wall consists of 2 shells • Large top shell (‘lid’): Epitheca • Small bottom shell (‘box’): Hypotheca • Cell wall contains silica