Algae

• Kingdom Protista: Algae

  1. Division Euglenophyta (Euglenoids)
  2. Division Pyrrophyta (Fire Algae or Dinoflagellates)
  3. Division Chlorophyta (Green Algae)
  4. Division Phaeophyta (Brown Algae)
  5. Division Rhodophyta (Red Algae)
• Division Euglenophyta (Euglenoids)

  Species: ~900

  Characteristics:

  • Known as the "missing link" due to plant and animal traits.
  • Freshwater, unicellular organisms with continually changing shape.
• Division Euglenophyta (Euglenoids)

  • Outer Covering: Pellicle.
  • Motility: Two flagella for movement.
  • Light Detection: Eyespot (red to orange) to perceive light direction.
  • Reproduction: Asexual via binary fission.
  • Energy Reserve: Paramylon (polysaccharide).
  • Special Traits:
  • Lose chlorophyll and ingest organic matter when grown in the dark.
  • Act as indicators of organic pollution.
• Division Pyrrophyta (Fire Algae or Dinoflagellates)

  Species: 2,000–4,000

  Characteristics:

  • Two flagella in grooves (belt-like and longitudinal).
• Division Pyrrophyta (Fire Algae or Dinoflagellates)

  • Covering: Cellulose plates with silica (silicon dioxide).
  • Energy Reserve: Oils and polysaccharides.
  • Photosynthetic Pigment: Fucoxanthin (yellow-brown carotenoid).
  • Special Traits:
  • Some colorless species ingest microorganisms.
  • Some forms cause red tide (blooms that turn water red).
  • Reproduction: Asexual via cell division (mitosis).
• Division Chlorophyta (Green Algae)

  Species: ~17,000

  Characteristics:

  • Structure: Biochemically uniform but diverse in form (siphonous, tubular, or sheet-like).
  • Energy Reserve: Starch (polysaccharide).
  • Cell Wall:
  • With cellulose (glucose).
  • With scales.
• Division Chlorophyta (Green Algae)

  • Reproduction:
  • Highly variable:
  • Asexual:
  • Unicellular forms: Cell division, forming spores (zoospores if motile and flagellated).
  • Multicellular forms: Fragmentation, where pieces grow into new individuals.
  • Sexual:
  • Isogamous: Gametes identical in size and appearance.
  • Anisogamous: Gametes differ in size/motility.
  • Oogamous: Female gamete larger and non-motile; male gamete smaller and motile.
• Division Chlorophyta (Green Algae)

  • Habitat:
  • Aquatic: Freshwater.
  • Terrestrial: Damp soil, cracks in tree bark, or moist places.
  • Symbiosis:
  • Found as endosymbionts in sponges, mollusks, and flatworms.
  • Grow with fungi to form lichens (dual organisms).
  • Ecological Importance:
  • Photosynthetic activity contributes to the oxygenation of water during daylight hours.
  • Integral part of the food web.
  • Shares significant traits with plants (pigments, energy reserves, cell wall composition), suggesting plants evolved from green algal-like ancestors.
• Division Phaeophyta (Brown Algae)

  General Characteristics:

  • Includes approximately 1,500 species.
  • Known as the "giants of the protists kingdom", with body sizes ranging from several centimeters to 75 meters.
  • Bodies can form tufts (growing in bunches), ropes, or thick, flattened branches.
  • Energy Reserve: Laminarin, a carbohydrate, serves as the main energy reserve.

  Reproduction:

  • Undergo sexual reproduction, alternating between haploid and diploid stages during their lifecycle.
• Division Phaeophyta (Brown Algae)

  Notable Members:

  • Kelps: The largest brown algae; tough and leathery.
  • Blades: Leaf-like structures.
  • Stipe: Stem-like structure.
  • Holdfast: Anchoring structure.
  • Gas-Filled Floats: Provide buoyancy, keeping the algae upright underwater.
• Division Phaeophyta (Brown Algae)

  Commercial Importance:

  • Cell Wall Composition: Contains polysaccharides called algin.
  • Algin Uses: Serves as a thickening and stabilizing agent in food and other products.
  • Forms underwater forests that serve as important marine ecosystems.
• Division Rhodophyta (Red Algae)

  General Characteristics:

  • Includes approximately 4,000 to 6,000 species.
  • Complex body forms, including interwoven filaments, delicate feathery structures, or flattened sheets of cells.

  Chloroplasts:

  • Contain pigments such as:
  • Phycoerythrin (red pigment).
  • Phycocyanin (blue pigment).
• Division Rhodophyta (Red Algae)

  Energy Reserve:

  • Polysaccharides in the form of floridean starch, which is similar to glycogen.

  Reproduction:

  • Sexual: Involves male and female gametes.
  • Asexual: Occurs through cell division or fragmentation.

  Habitat:

  • Found in warm tropical oceans, freshwater, and soil.
  • Some species incorporate calcium carbonate (CaCO₃) into their cell walls.
• Division Rhodophyta (Red Algae)

  Commercial Importance:

  • Cell Wall Composition: Rich in polysaccharides.
  • Agar: Used as a food thickener and in culture media.
  • Carrageenan: A food additive for texture and stability.
  • Edibility:
  • Can be consumed fresh, dried, or toasted.

  Nori (Porphyra sp.): Popular in Japan, used in sushi, soups, noodle dishes, sauces, and as flavoring.