طحالب

General Characteristics of Green Algae

• Division: Chlorophyta
• Phylum: Green Algae
• Mostly aquatic, 10% are terrestrial.
• Found in freshwater and saltwater; some even grow on land, trees, rocks, and other plants or algae.
• Some form lichens with fungi.

Thallus Organization

• Shows variability in forms.
  • Unicellular Forms:
    • Motile: Chlamydomonas
    • Non-motile: Chlorella
  • Multicellular Forms:
    • Colonial Forms
      • Coenobium (e.g., Volvox, Pediastrum)
      • Palmelloid Aggregation (e.g., Palmella)
    • Filamentous Forms
      • Unbranched (e.g., Spirogyra, Ulothrix)
      • Branched (e.g., Oedogonium)

Flagella

• Present in some motile genera or motile reproductive stages.
• Vary in number (1 to 4 or more).
• Equal in length; emerge from the anterior or apical end of the cell.
• Typically have a smooth surface (whiplash type).

Reserve Food

• Carbohydrate reserves (starch) similar to those in seed plants.
• Stored in the cytoplasm or within pyrenoids (single or multiple) in the chloroplast.

Eyespot

• A bright red or reddish-brown pigmented spot found in motile vegetative or reproductive cells, located on the chloroplast.
• Acts as a light receptor ("eye" of the cell).
• Involved in phototaxis (light-dependent movement).

Reproduction

• Vegetative, asexual, and sexual reproduction methods observed.
• One or more methods may be used.
  • Vegetative: cell fragmenting;
  • Asexual: forming zoospores (motile) or aplanospores (non-motile).
  • Sexual: involving isogamy, anisogamy, and oogamy.

Life Cycle

• Different life cycles observed in chlorophyta including :
• Diplontic
• Haplontic
• Isomorphic Haplodiplontic
• Heteromorphic Haplodiplontic

Specific Genera and Families (examples)

• Chlamydomonas, Gonium, Pandorina, Eudorina, Hydrodictyon, Pediastrum, Scenedesmus, Spirogyra, and Oedogonium, Ulva, Volvox

• Volvocaceae, Hydrodictyaceae, Scenedesmaceae, Zygnemataceae, Ulvaceae, etc.

• Features: like cell shape, colony structure (coenobium), methods of reproduction, etc. are highlighted in the additional information provided.

Additional Information:

• Detailed descriptions of different species (e.g., Volvox, Chlamydomonas) are provided.
• Methods of asexual and sexual reproduction are explained.
• Importance of morphological features are discussed.
• Diagrams (figures) are included to help in understanding the structures and life cycles of different genera.
• Additional information, including details about zoospores or aplanospores, etc

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