Chlorophyta Study Notes

Chlorophyta Overview

  • Definition: Chlorophyta (green algae) are plant-like microorganisms that produce energy via photosynthesis.

General Characteristics

  • Cell Structure: Unicellular, multicellular, colonial, coenocytic (single large cell).
  • Habitat: Aquatic (freshwater and marine), some terrestrial.
  • Symbiosis: Forms lichens with fungi and symbiotic relationships with animals like Hydra.

Reproduction

  • Asexual Methods: Fission, budding, fragmentation, zoospores.
  • Sexual Methods: Isogamous, anisogamous, oogamous. Alternate between haploid and diploid phases.

Taxonomy of Chlorophyta

Phylum: Chlorophyta

Classes:

  • Chlorophyceae: Largest class, 429 genera, 6500 species, predominantly freshwater.
  • Prasinophyceae
  • Ulvophyceae
  • Charophyceae
  • Trebouxiophyceae

Classification Features:

  1. Cell wall mainly consists of cellulose.
  2. Flagella (2-4) with a 9+2 arrangement.
  3. Eukaryotic cells, usually uninucleate or coenocytic.
  4. Chloroplasts with pyrenoid(s) present.

Orders of Chlorophyceae

  • Volvocales:

    • Characteristics: Unicellular to motile colonies.
    • Reproduction: Asexual (zoospores) and sexual (isogamous, anisogamous, oogamous).

  • Chlamydomonadales:

    • Structure: Two anterior flagella, contractile vacuoles, eye spot, cup-shaped chloroplast.
    • Nutrition: Autotrophic via photosynthesis.

Order: Volvocales and Reproduction

  • Asexual Reproduction: Formation of gonidia, develops into daughter colonies.
  • Sexual Reproduction:
    • Monoecious (same) or dioecious (different)
    • Development of androgonidia (male) and oogonia (female).

Examples of Chlorophyta

  • Volvox:
    • Colonial organization; asexual and sexual reproduction through inversions and zygote formation.
  • Chara and Nitella (Charophyceae): Most closely related to terrestrial plants, exhibit both vegetative and sexual reproduction.

Ulvophyceae Characteristics

  • Filamentous structures, asexual and sexual reproduction.

Life Cycle of Chara

  • Vegetative Reproduction: Amylum stars, bulbils.
  • Sexual Reproduction: Oogamous, signaling advanced reproductive processes.