Chapter 18:  Algae

In this chapter you will learn about

At the end of this chapter the successful student will be able to

• Recognize common Green Algae of Phylum Cholorophyta and in general describe their lifecycle
  • Chlamydomonas
    • reproduces either asexually  or sexually
    • life cycle animation
  • Ulothrix
    • reproduces either asexually or sexually
  • Spirogyra (watersilk)
    • reproduces either asexually or sexually
  • Oedogonium
    • reproduces either asexually or sexually
• List the other Algae 
  • Phylum Chromophyta
    • Yellow-Green Algae
    • Golden-Brown Algae
      • Diatoms
        • Human and ecological relevance:
    • Brown Algae
  • Phylum Rhodophyta
    • Red Algae (sea weeds)
      • Human and ecological relevance:
• Recognize common Algae of Phylum Euglenophyta 
  • euglena
• Recognize common Algae of phylum Dinophyta
  • Dinoflagellates
    • Human and ecological relevance
• Assignments
• Glossary

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Common Green Algae of Phylum Cholorophyta

• The Green Algae
  • Includes about 7,500 species that occur in a rich variety of forms and occur in diverse, widespread habitats.
    • Greatest variety found in freshwater lakes, ponds, and streams.
    • Most have a single nucleus.
    • Most reproduce both sexually and asexually.
• Chlamydomonas
  • Common inhabitant of freshwater pools.
    • Pair of whip-like flagella on one end pull the cell through the water.
    • Single, cup-shaped chloroplast with one or two pyrenoids inside.
      • Proteinaceous structures thought to contain starch synthesis enzymes.
  • Asexual Reproduction
    • Nucleus divides by mitosis, and cell contents become two daughter cells within the cellulose wall.
      • Develop flagella and swim away.
  • Sexual Life Cycle of Chlamydomonas
    •  
      Click here to see the life cycle animation
• Ulothrix
  • Thread-like alga.
    • Single row of cylindrical cells forming a filament.
      • Basal cell functions as a holdfast.
  • 
• Spirogyra (Watersilk)
  • Common freshwater algae consisting of unbranched filaments of cylindrical cells.
    • Frequently float in masses at the surface of quiet waters.
  • Asexual Reproduction
    • Fragmentation of existing filaments.
  • Sexual Reproduction
    • Papillae fuse and form conjugation tubes.
    • 
• Oedogonium
  • Epiphytic filamentous green alga.
    • Each cell contains a large, netlike chloroplast that rolls and forms a tube around and toward the periphery of each protoplast.
  • 

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Other Algae

• The Yellow-Green Algae (Xanthophyceae)
  • Mostly freshwater organisms with a few marine and terrestrial representatives.
    • Two flagella of motile cells are oriented in opposite directions.
      • Aplanospores formed during asexual reproduction.
      • Sexual reproduction rare.
• The Golden-Brown Algae (Chrysophyceae)
  • Most occur in the plankton of bodies of fresh water.
    • Motile cells have two flagella of unequal length inserted at right angles to each other.
      • Photoreceptor on short flagellum
  • The Diatoms (Bacillariophyceae)
    • Among best known and economically most important members of this phylum.
      • Mostly unicellular
        • Occur in both fresh and salt water.
          • Particularly abundant in colder marine habitats.
    • 
    • Human and Ecological Relevance of Diatoms
      • Oils are sources of vitamins.
      • Diatomaceous Earth
        • Filtration
        • Polishes
        • Reflectorized Paint
• The Brown Algae (Phaeophyceae)
  • Relatively Large
  • Most Marine
  • Non-Unicellular or Colonial
  • Many have a thallus differentiated into a holdfast, a stipe, and blades.
    • Blades may have gas-filled bladders.
  • Sargassum - Floating Brown Seaweed
  • Fucus - Common Rockweed
  •  
• The Red Algae
  • Most species are seaweed.
    • Tend to occur in warmer and deeper waters than brown algae.
  • Most are filamentous.
  • Relatively complex life cycle involving three types of thallus structures.
  • Colors mostly due to phycobilins.
  • Numbers of species produce agar.
  • 
  • Human and ecological relevance: 
    • Agar is used around the world in laboratories and medical institutions as a solidifier of nutrient culture media for the growth of bacteria.  Orhid tissue are cultured commercially on such media.  

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Phylum Euglenophyta

• The Euglenoids
  • Spindle-shaped.
  • No cell wall, thus changes shape as it moves.
    • Sub-membrane strips and membrane form pellicle.
  • Contains gullet.
  • Contains red eyespot.
  • Reproduction by cell division
  • euglena
  • 

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Phylum Dinophyta

• The Dinoflagellates
  • Unicellular
  • Contain two flagella.
    • One trails behind the cell.
    • Other encircles the cell at right angles.
  • Most have disc-shaped chloroplasts.
    • Contain xanthophyll pigments.
  • Many have tiny projectiles.
  • Many types of toxins produced. (Red Tides)

  • http://www.gardenbuildingsdirect.co.uk/Article/what-is-harmful-algae.

  • 
  • Human and ecological relevance
    • These produce red tide, produce powerful neurotoxins that accumulate in shell fish.  About 2000 people become ill each year, with 15% fatally from eating contaminated shell fish.  3 major dinoflagellate toxins have been studied for possible use in chemical warfare.

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Last modified: October 08, 2004 by Cynthia Herbrandson  © Copyright 1999, Kellogg Community College. All rights reserved.