Protist

• Protists


  Simple eukaryotic organisms that are neither plants nor animals or fungi
• Protists


  • Unicellular in nature but can also be found as a colony of cells
  • Most protists live in water, damp terrestrial environments or even as parasites
• Euglena


  A eukaryotic protist
• Protista


  Derived from the Greek word "protistos", meaning "the very first"
• Protists


  • Usually unicellular and the cell contains a nucleus which is bound to the organelles
  • Some possess structures that aid locomotion like flagella or cilia
• Protists form a link between plants, animals and fungi as these three kingdoms diverged from a common protist-like ancestor, billions of years ago
• Protists are traditionally considered the first eukaryotic forms of life and a predecessor to plants, animals and fungi
• Characteristic features of Kingdom Protista

  • They are eukaryotic organisms with a membrane-enclosed nucleus
  • They are usually aquatic, present in the soil or in areas with moisture
  • Most are unicellular, but some are multicellular
  • They may be autotrophic or heterotrophic
  • Symbiosis and parasitism are observed
  • They exhibit locomotion through cilia and flagella, or pseudopodia
  • They reproduce asexually, with sexual reproduction being rare
• Classification of Protista


  • Protozoa
  • Slime Moulds
  • Chrysophytes, Dinoflagellates and Euglenoids
• Protozoa


  Unicellular organisms, historically called "animal" protists as they are heterotrophic and showed animal-like behaviours
• Major groups of Protozoa

  • Amoeboid protozoans
  • Flagellated protozoans
  • Ciliated protozoans
  • Sporozoans
• Slime Moulds


  Saprophytic organisms that feed on dead and decaying matter, with many nuclei and visible aggregates called plasmodium
• Chrysophytes, Dinoflagellates and Euglenoids


  • Single-celled or multicellular, photosynthetic organisms found in freshwater or marine environments, with a stiff cell wall
• Chrysophytes


  • Diatoms, golden algae
• Dinoflagellates


  Photosynthetic organisms that show bioluminescence and can cause red tide
• Euglenoids


  Link between plants and animals, lacking a cell wall but performing photosynthesis, with a protein-rich outer body covering called a pellicle
• Economic importance of Protists

  • Serve as the foundation of the food chain
  • Act as symbionts
  • Produce oxygen and may be used to produce biofuel
  • Primary sources of food for many animals
  • Harvested by humans for food and other industrial applications
  • Phytoplankton is a sole food source for whales
  • Seaweed is a plant-like protist
  • Zooplankton is fed on by various sea creatures
• Protozoa


  unicellular organisms, animal protists
• Ameboid protozoans


  it has pseudopodia
• Flagellated protozoans


  free-living as well as parasitic
• Ciliated protozoans


  covered by cilia which help in locomotion and nutrition
• Sporozoans


  spore-like life stages
• Slime moulds are visible to the naked eye.