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Protista: Algae and Heterotrophic
• diverse group of organisms, comprising those eukaryotes that are not animals, fungi, or plants. They are usually treated as the kingdom Protista
• photosynthetic organisms that occur in most habitats.
• vary from small, single-celled forms to complex multicellular forms- giant kelp 65 meters in length.
• regarded as simple plants, they actually span more than one domain, including both Eukaryota and Bacteria (see Blue- green algae), as well as more than one kingdom, including plants and protists, the latter being traditionally considered more animal-like (see Protozoa).
• All lack leaves, roots, flowers, seeds and other organ structures that characterize higher plants (vascular plants).
• All algae have photosynthetic machinery ultimately derived from the cyanobacteria, and so produce oxygen as a byproduct of photosynthesis
• algae produce about 73 to 87 percent of the net global production of oxygen
• far more common in moist, tropical regions than dry ones, because algae lack vascular tissues and other adaptations to live on land.
• Algae can endure dryness and other conditions in symbiosis with a fungus as lichen.
Role in Aquatic Ecology
• Microscopic forms that live suspended in the water column — called phytoplankton — provide the food base for most marine food chains.
Ecology of algae • Play a role comparable to the role played by plants in the far young
terrestrial world. • Dominant in freshwater habitats • Ponds • Streams • Lakes
• Seaweeds • Members of red, brown and
• At low tides can see distinct layers that can withstand large fluctuations of humidity, temperature, salinity and light
• Beyond the zone of waves massive brown kelps form forest
• Provide shelter for diverse fish and invertebrate animals
• Plankton- minute photosynthetic cells along with tiny animals
• Phytoplankton- photosynthetic algae and cyanobacteria
• Phytoplankton is the beginning of the food chain for heterotrophic organisms that live in oceans of bodies of freshwater
Protista: Algae and Heterotrophic Protists
• Dinoflagellates : Phylum Dinophyta • Euglenoids: Phylum Euglenophyta • Cryptomonads: Phylum Cryptophyta • Haptophytes: Phylum Haptophyta • The Heterokonts- oomycetes, diatoms, pyhaeophyta • Red Algae: Phylum Rhodophyta • Green Algae: Phylum Chlorophyta • The Slime Molds
Marine Phytoplankton • Dinoflagellates- Phylum
Dinophyta • Euglenoids: phylum • Haptophytes: phylum • Heterokonts- Oomycetes,
Most important eukaryotic members of the marine phytoplanton and therefore essential to the support of marine animal life
Algae and “The Carbon Cycle” • Algae are able to transform carbon dioxide into carbohydrates or into
calcium carbonate • Today phytoplankton absorb about One-half of all the Carbon dioxide that
results from human activities • White cliffs of Dover- calcium carbon deposits “CO2 drawdown” effect •
Dinoflagellates: Phylum Dinophyta
• Molecular systematic data- Related to ciliated protozoa such as Paramecium and Vorticella
• Unicellular biflagellates • Marine and freshwater • Some dinoflagellates are nonmotile • Reproduction- longitudinal cell division
• About half lack a photosynthetic mechanism
• Ingest solid food particles (tubular process peduncle suction organic material)
• Or absorb dissolved organic compounds • Many photosynthetic dinoflagellates can
feed in these ways- • Mixotrophy- the ability to utilize both
organic and inorganic carbon sources.
• Zooxanthellae- responsible for the photosynthetic productivity that makes possible the growth of coral reefs in tropical waters
Dinoflagellates produce toxic or bioluminescent compounds
• Toxic glycoside released by activated dinoflagellate cysts
• Paralyze the respiratory tract, dinoflagellates feed on fish then return to cyst stage
Euglenoids: Phylum Euglenophyta
• Earliest euglenoids were phagocytes • Mostly Freshwater • Contain chloroplast • Studies suggest that euglenoids were
derived from endosymbiotic green algae • 2/3 are colorless heterotrophs that rely
upon particle feeding or absorption • Euglena
Euglena • Unicellular • Lacks cell wall or
rigid structure covering plasma membrane
• Beneath plasma membrane pellicle
• Swimming Euglena have a single long external flagellum
Crytomonads; Phylum Crytophyta
Haptophytes : Phylum Haptophyta
• Mostly Marine phytoplankton • Few freshwater and terrestrial forms are
known • Unicellular flagellates, colonial flagellates,
colonial flagellates and non-motile single cells and colonies
• Haptonema- threadlike structure that extends from the cell and can help catch prey, and sensory