Protozoans Quiz: Ciliates and More

Topic 11: Domain Eukarya 1: Protista

• Protists are a diverse group of eukaryotic organisms, commonly single-celled, but sometimes multicellular.
• They are not part of plants, animals, or fungi.
• Protists vary greatly in their organization, some being single-celled, multicellular, or forming filaments or colonies.
• Not all are microscopic; some can be as large as 200 meters.
• Common size range from 5 µm to 2 or 3 mm.
• Some are parasitic, and some are free-living algal protists.

Learning Outcomes

• Describe the general characteristics of Protista
• State the classification of Protista into two major phyla of algae and four major phyla of protozoa
• Describe the unique characteristics of algae
• Describe the unique characteristics of protozoa
• State the importance of Protista

Subtopic 11.1: General Characteristics of Protista

• Members of domain Eukarya
• Eukaryotic, having a nucleus and membrane-bound organelles
• Algae, protozoa, water molds, and slime molds
• Primarily aquatic
• Diverse body forms, types of reproduction, modes of nutrition, and lifestyles

Subtopic 11.2: Classification of Protista

• Protist classification is evolving, with molecular analysis and ultrastructure data revealing phylogenetic relationships.
• Data suggests protists are paraphyletic.
• Currently, protists and other eukaryotes are split into five informal supergroups: Excavates, Chromalveolates, Rhizarians, Archaeplastids and Unikonts.

Subtopic 11.2, Algae

• Algae are photosynthetic organisms.

• Contain chlorophyll, used for photosynthesis

• Can be either unicellular or colonial, the latter occurring as aggregates of cells.

• Found in salt or fresh waters, or on the surfaces of soil or rocks.

• Multicellular algae have tissues but lack true stems, leaves, or roots

• Two Major Phyla:

• Phylum Chlorophyta (green algae): Most are aquatic, some terrestrial

• Contain chlorophylls a and b, store food as starch

• Examples: Chlamydomonas, Volvox

• Phylum Phaeophyta (brown algae): Many familiar seaweeds

• Contain chlorophylls a and c, carotenoids like fucoxanthin

• Examples: Fucus, has blades, stipe, and holdfast

• Body (thallus), which may lack roots, stems, or leaves with blade, stipe and holdfast

Subtopic 11.2, Protozoa

• Heterotrophic

• Mixotrophic

• Generally motile with flagella, cilia, or pseudopodia for movement

• Strictly non-multicellular, existing as single cells or colonies

• Diverse, widespread in aquatic and terrestrial habitats

• Classification:

• Phylum Euglenophyta (e.g., Euglena): Freshwater, some photosynthetic (autotrophic), some ingest or absorb food (heterotrophic)

• Phylum Rhizopoda (e.g., Amoeba): Use pseudopodia, heterotrophs

• Phylum Ciliophora (e.g., Paramecium): Covered in cilia, heterotrophs

• Phylum Apicomplexa (e.g., Plasmodium): Parasitic, spore-forming, lack locomotion

Subtopic 11.3: Importance of Protista

• Major components of plankton, primary producers in aquatic ecosystems.
• Play a basic role in food chains
• Provide food and oxygen to other organisms
• Seaweeds are a food source, providing essential nutrients.
• Examples: Kelp, Laminaria, Porphyra
• Spirulina is a source of vitamins, minerals, amino acids, carbohydrates, and enzymes
• Chlorella is a source of protein, fats, vitamins, and contributes to growth and tissue repair
• Eutrophication: Excess nutrients cause algal blooms, which deplete dissolved oxygen, harming aquatic organisms.
• Red tides: Dinoflagellates produce neurotoxins, causing poisoning in shellfish and affecting marine life
• Human health: Some protists cause diseases, such as malaria in humans, caused by parasitic protists.