Algae: Protophytic & Thallophytic Levels

• Algae possess varying levels of structural organization.

Protophytic Level

• Characterized by single-celled algae.

• Without a Nucleus (Prokaryotic, No Flagella):

  • Chroococcus is a round cyanobacteria (blue-green algae).

• With a Nucleus (Eukaryotic, No Flagella):

  • Diatoms are minute algae distinguished by glass-like cell walls and diverse shapes.

• With a Nucleus & Flagella (Monads, Capable of Movement):

  • Euglena navigates using a flagellum.
  • Peridinium is a dinoflagellate with armor-like plates.
  • Chlamydomonas is a green alga propelled by two flagella.

Thallophytic Level

• Indicates multicellular algae with a simple structure.

• Colonial (Living in Groups):

  • Volvox creates mobile spherical colonies.

• Filamentous (Cells in Chains):

  • Nostoc resembles beads on a string.
  • Zygnema consists of an unbranched chain.
  • Scytonema exhibits false branches.
  • Stigonema features true branches and multiple rows of cells.

• Tissue-Like (More Complex Grouping):

  • Digenea simplex forms a tissue-like structure.
  • Ulva (Sea Lettuce) forms thin, flat seaweed.
  • Ascophyllum nodosum has internal layers similar to a plant.

• Tube-Like Algae (Giant Multinucleate Cells):

  • Cladophora appears as filaments.
  • Caulerpa is a single giant cell with multiple nuclei.
  • Codium has a sponge-like texture.

Cormophytic Level

• Encompasses true plants with vascular tissues.

• Posidonia oceanica is a seagrass with a vascular system (xylem & phloem).

Thallus (Body Shape) & Growth Strategies

• Algae exhibit a variety of shapes and growth forms.
• Basic Forms:
  • Encrusting algae grow as a flat crust attached to surfaces.
  • Prostrate algae lie flat, attaching via root-like structures.
  • Cespitose algae grow in dense, grass-like clumps.
  • Erect algae stand upright with a narrow base.
• Different Shapes:
  • Filamentous algae resemble thin threads.
  • Tree-like (Arborescent) algae feature:
    • Fine branches that end in tiny, delicate filaments
    • Uniformly thick branches
  • Sheet-like (Laminar) algae are flat, thin structures.
• Branching Patterns:
  • Dichotomous branching splits into two equal branches.
  • Lateral branching grows branches from the side.
  • Pectinate branching is comb-like, with branches on one side.
  • Pinnate branching has alternating or evenly spaced branches.
  • Three-dimensional growth occurs in all directions.
  • Verticillate branching forms circular (whorl) patterns.
  • Basal branching originates from the base.

Growth Types

• Algae exhibit different growth patterns.
• Diffuse growth involves any cell dividing and growing.
• Apical growth is limited to the tip.
• Marginal growth occurs at the edges.
• Trichothallic growth results in normal and protective cells.

Quick Lab Guide

• To examine algae, essential tools include:
  • Microscope & slides for observing tiny structures
  • Scalpel & teasing needle for separating and preparing samples
  • HCl & Petri dishes for chemical testing

Explore the structural diversity of algae, from single-celled organisms (protophytic level) like Chroococcus and diatoms to multicellular forms (thallophytic level) such as Volvox and Zygnema. Learn how algae are classified.