Lecture Notes: Protists

Overview

• Protists are a diverse group of eukaryotic organisms that do not fit into the categories of plants, animals, or fungi.
• Historically classified in a single kingdom called Kingdom Protista, but classifications have evolved.
• Most eukaryotic organisms are protists.

Characteristics of Protists

• Unicellular: Most protists are single-celled but complex.
• Eukaryotic Features: Have membranous organelles and DNA enclosed in a nucleus.
• Cell Structure: Lack a cell wall made of cellulose (like plants) or chitin (like fungi).
• Metabolism: Can be autotrophs (photosynthetic), heterotrophs (consumers), or mixotrophs (like Euglena).
• Reproduction: Can reproduce sexually (gamete exchange) or asexually (binary fission).
• Locomotion: Move using pseudopodia, cilia, or flagella.
• Environment: Thrive in moist environments such as water, moist soil, and animal body fluids.

Types of Protists

Protozoans (Animal-like Protists)

• Amoebas: Shapeless, aquatic, move with pseudopodia, and are predators.
  • Pathogens: Some cause diseases like amoebic dysentery and brain-eating amoeba (Naegleria).
• Ciliates: Move using cilia; example includes Paramecium.
  • Paramecium includes features like contractile vacuoles and both macro and micronuclei.
  • Can reproduce through binary fission and conjugation (genetic exchange).
• Flagellates: Move with flagella; examples include Trypanosoma (causes sleeping sickness) and Giardia.
• Sporozoans: Non-motile parasites; Plasmodium causes malaria.

Plant-like Protists (Algae)

• Photosynthetic: Can be multicellular or unicellular.
• Oxygen Production: Contribute to 50% of Earth’s oxygen.
• Diatoms: Have silica glass shells, used in various industries.
• Dinoflagellates: Part of the phytoplankton, can cause bioluminescence.
• Green Algae: Includes organisms like Volvox, which are colonial and show early multicellular characteristics.

Fungus-like Protists

• Includes slime molds with over 900 species.

Importance of Protists

• Form symbiotic relationships, e.g., coral reefs and termite guts.
• Base of aquatic food chains.
• Significant oxygen producers and CO2 consumers.
• Potential for biofuel production from algae.

Summary

• Protists are incredibly diverse and play various ecological roles, from being disease vectors to being foundational components of ecosystems and potential resources for renewable energy.