Study Notes on Plant-Like Protists and Algae L4

PLANT-LIKE PROTISTS

INTRODUCTION TO ALGAE

• Definition: Aquatic, photosynthetic, eukaryotic organisms.
• Habitat: Can be found in fresh or salt water.
• Importance:
  • Essential in both fresh and saltwater ecosystems.
  • Forms the basis of food chains in aquatic ecosystems.

ALGAE LECTURE OBJECTIVES

• Understanding the following key concepts:
  • What are algae?
  • Classification of algae.
  • Algal diversity, including body forms, pigments, life cycle, habitat, and reproduction (syngamy).
  • Various algal body forms.
  • Identification of three categories of protist body plans – unicellular, colonial, and multicellular.
  • Adaptations of algae to aquatic habitats.
  • Characteristics of the major algal groups: Chlorophyta, Phaeophyta, and Rhodophyta.

CLASSIFICATION OF ALGAE

• Domain: Eukaryota
  • Kingdom: Plantae (Viridiplantae) includes green plants.
  • Division:
  • Chlorophyta (Green algae).
• Domain: Eukaryota
  • Kingdom: Protoctista
  • Divisions:
  • Phaeophyta (Brown algae).
  • Rhodophyta (Red algae).

ALGAL BODY FORMS/PLANS

Unicellular Algae

• Unicellular motile cells do not adhere following karyokinesis and cytokinesis.
• Hypothesis: All algal body forms may have evolved from a common unicellular ancestor, specifically Clamydomonas sp.

Colonial Algae

Motile Colonies

• Definition: Unicellular organisms adhere together in a matrix.
• Characteristics: All cells in the colony are flagellated and do not adhere by the middle lamella after karyokinesis and cytokinesis (binary fission).
• Example: Volvox sp.

Non-Motile Colonies

• Characteristics: Cells are held together in a gelatinous matrix and may lose or never develop flagella.

Filamentous Body Forms (Multicellular)

Simple Filamentous

• Characteristics: Cells are joined together end to end and are held by middle lamella following karyokinesis and cytokinesis.
• Example: Spirogyra (Filamentous green algae).

Branched Filamentous

• Characteristics:
  • Cells divide transversely (karyokinesis + cytokinesis) in a regular manner in one plane.
  • Occasionally, cells may also divide longitudinally.
  • Portions of the body vary (e.g., holdfast for anchorage, sporangia, and gametangia).
• Example: Cladophora sp.

Membranous Body Forms (Multicellular)

• Characteristics:
  • Formation of a membranous sheet.
  • Cell division is precisely controlled in both x and y planes.
  • Regular division occurs in two planes, creating a sheet.

Differentiated Thallus (Multicellular)

• Characteristics:
  • Cell division occurs in all three planes: x, y, and z.
  • Results in a bulky, three-dimensional parenchymatous body.

Coenocytic Structures (Unicellular)

• Definition: Coenocytic or siphonous body type where karyokinesis occurs without cytokinesis, resulting in giant multinucleated cells.
• Characteristics: Cells may enlarge to form bulbous structures.
• Example: Caulerpa sp.

Coenocytic or Tubular Structures

COMPARATIVE BODY PLANS

• Body plans available in algae include unicellular, colonial, and multicellular types.
• Land plants are exclusively multicellular.

ECOLOGICAL ADAPTATIONS OF ALGAE

Morphological Adaptations

• Examples include branched body form, holdfast for anchoring, and rhizoids for attachment.

Physiological Adaptations

• Different pigments assist in light absorption.
• Adaptations in reproductive strategies, such as timing of gamete release and the presence of motile gametes.

Other Adaptations

• Structures like stolons and rhizomes for growth and reproduction.

FACTS ABOUT ALGAE

• Total weight of all algae exceeds that of all terrestrial plants.
• Algae are critical for life in ocean ecosystems; without them, marine environments would be lifeless and land uncolonized.

CHARACTERISTICS OF ALGAL GROUPS

Chlorophyta (Green Algae)

• Size: Includes both micro and macroalgal forms.
• Pigments: Contains chlorophylls a and b, which absorb red light.
• Storage Carbohydrates: Primarily starch.
• Habitat: Mainly found in fresh water, with some in marine tropical waters (depths of 0 - 30m).
• Body Forms: Unicellular, colonial (both motile and non-motile), filamentous, and thalloid forms.

Phaeophyta (Brown Algae)

• Size: Typically macroalgae.
• Pigments: Contains fucoxanthin and chlorophylls a and c, which absorb blue light.
• Storage Carbohydrates: Primarily laminarin and mannitol.
• Life Cycle: Exhibits sporic and gametic life cycles.
• Habitat: Almost exclusively marine, and abundant along rocky shores, especially in the north temperate zone.
• Body Forms: Filamentous, thalloid ribbon-shaped, and differentiated thallus.

Rhodophyta (Red Algae)

• Size: Primarily macroalgae.
• Pigments: Contains phycoerythrin (absorbs green light), as well as chlorophylls a and d.
• Storage Carbohydrate: Carrageenin (found in sea moss).
• Habitat: Mostly marine, often found in deep warm waters.
• Body Forms: Filamentous and branched thalloid forms.

MULTIPLE CHOICE QUESTIONS

Question 1

• Which body plans are found in the algae?
  • A. multicellular, colonial, and unicellular
  • B. multicellular
  • C. unicellular
  • D. unicellular and colonial

Question 2

• Photosynthetic pigments of the Rhodophyceae (Red algae) are:
  • A. Chlorophyll ‘a’ and ‘b’
  • B. Chlorophyll ‘a’ and ‘c’, fucoxanthin
  • C. Chlorophyll ‘a’ and ‘d’
  • D. Chlorophyll ‘a’ and ‘d’ and phycoerythrin

LITTORAL ZONE

• Supralittoral: The splash zone, not washed by tides, where organisms are exposed to terrestrial conditions.
• Eulittoral: The zone between high and low water tide marks with severe conditions for organisms.
• Sublittoral: The continuously submerged zone with less severe life conditions.

AQUATIC ENVIRONMENTS

Marine Environments

• Include:
  • Open ocean
  • Shoreline (littoral zone or intertidal zone)
  • Benthic (ocean floor)

Freshwater Environments

• Include:
  • Deep lakes
  • Still shallow ponds
  • Slow flowing streams
  • Fast flowing streams
  • Coastal wetlands