Members of Kingdom Protista

Are plant-like, but definitely not plants!

Base of aquatic food chains

Lack cuticle on epidermis - totally dependent on aquatic environment for life cycle

Gametophytes are usually unicellular

Lack vascular tissues (except kelps have a phloem like tissue)

Brown Algae

About 1500 spp - mostly multicellular

Economically important

- Algin (thickening and stabilizing agent in foods and cosmetics)
- Significant food source
- Source of commercial Iodine

Red Algae

About 4000 spp - some unicellular

Some incorporate Calcium Carbonate into their cell walls -- important reef builders

Economically important

- Agar -- used in culturing media
- Agarose -- molecular biology research (gels)
- Carageenan -- smoothing agent for foods and cosmetics
- Source of vitamins and minerals

Green Algae

About 7000 spp - unicellular, colonial and multicellular

Have many characteristics in common with land plants (photosynthetic pigments, cell wall composition, cell storage molecules)

Many unicellular algae are partners in symbiotic relationships (animals and fungi)

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Last updated April 4, 1997.