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::: What are seaweeds? Morphology and Taxonomy Reproduction & Life cycles Ecology and distribution Importance and Economic uses Seaweed resources of Taiwan Seaweeds of northeastern Taiwan Search of species of Taiwan seaweeds sitmap Educational activity Game Extension learning Wallpaper
icon Introduction
icon Morphology
  photo Appearance
photo Branching
photo Growth
photo Cell Structure
photo Plastid or Chloroplast
photo Holdfast
photo Asexual Reproduction
photo Sexual Reproduction
icon Taxonomy
  photo Chlorophyta
photo Phaeophyta
photo Rhodophyta
photo Cyanophyta
Search of species of Taiwan seaweeds sitemap Educational activity Game Extension learning Wallpaper
photo  Algae have a great variety of forms, sizes and colors. Some are simple colonies with many cells; some are filamentous, tubular, meshed, membranous or saccate algae. Some are more delicate and complex, such as, Sargassum having structures similar to roots, stems and leaves of plants as well as differentiated air bladders which help the algae floating to water surface to be able to absorb more sunlight. Nevertheless, although algae may have different forms, their internal structures are composed of similar cells with simple differentiation instead of true roots, stems or leaves.

  The taxonomy of algae is mainly based on the following features: the pigments (or colors), photosynthetic products, composition of the cell wall, number of flagella, position of the flagella, cell structures, growth patterns, branching, holdfasts, types of sporangia, carpogonial branches and cystocarps.
  The table below shows the main characteristics and differences between blue-green algaeCyanophyta)、green algaeChlorophyta)、brown algaePhaeophyta)and red algaeRhodophyta):
Phylum Pigment Photosynthetic product(s)
Cell wall Flagellum Cell nucleus Form Note
Green algae (Chlorophyta) chlorophyll a and b, α, β-carotene, lutein starch cellulose biflagellate; equal in length; apical Yes unicellular, colonies or multicellular
Widely distributed; both terrestrial and marine, ca.1,200 species worldwide.
Brown algae (Phaeophyta) chlorophyll a and c, fucoxanthin, β-carotene, lutein laminaran, mannitol cellulose, alginate biflagellate; not equal in length; lateral or not flagellum Yes multicellular 99.7% marine, ca. 2,000 species worldwide.
Red algae (Rhodophyta) chlorophyll a,d; a, phycoerythrin, phycocyanin, α, β-carotene floridean starch Cellulose, carrageenan or agarose
No Yes Uni- or multi-cellular 98% marine, ca. 6,000 species worldwide.
Blue-green algae (Cyanophyta) Chlorophylla; phycocyanin, phycoerythrin, β-carotene, lutein glycogen, cyanophycean starch glycoprotein cellulose No No unicellular; colonies Mostly freshwater (75%), some marine.
  In the past, there were only three biological kingdoms i.e. Animalia (animal), Plantae (plant) and Protozoa. As algae have cell walls and chlorophyll a for photosynthesis, they were classified under Plantae. However there are five kingdoms in biology: Protista, Monera, Fungi, Plantae and Animalia. Since algae do not have vascular tissue, they no longer belong to the Planta kingdom. Instead, they are now placed in two kingdoms: Protista and Monera. Blue-green algae belong to Monera. Green algae, red algae and brown algae belong to Protista.
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Updated: Jan 30, 2007