Protista - NCERT Notes

Kingdom Protista - NCERT Based

General Characteristics (NCERT)

  • Eukaryotic, primarily aquatic organisms
  • May be photosynthetic (plant-like), heterotrophic (animal-like) or saprophytic (fungus-like)
  • Reproduction: Both asexual (cell fusion) and sexual (zygote formation)
  • Forms a link with plants, animals and fungi

1. Chrysophytes

Includes:

  • Diatoms (Golden algae):
    • Siliceous cell walls forming two thin overlapping shells
    • Example: Navicula
  • Desmids (Freshwater algae)

💡 NCERT Fact: Diatomaceous earth used in polishing, filtration

2. Dinoflagellates

  • Marine, photosynthetic
  • Cell wall has stiff cellulose plates
  • Two flagella (one longitudinal, one transverse)
  • Examples:
    • Gonyaulax - Causes red tides
    • Noctiluca - Bioluminescent

3. Euglenoids

  • Freshwater organisms with protein-rich layer called pellicle
  • Mixotrophic (photosynthetic in light, heterotrophic in dark)
  • Example: Euglena

4. Slime Moulds

  • Saprophytic protists
  • Form aggregates under unfavorable conditions (plasmodium)
  • Example: Physarum

5. Protozoans (NCERT Classification)

Type Characteristics Examples Diseases
Amoeboid Pseudopodia for movement Entamoeba Amoebic dysentery
Flagellated Flagella for locomotion Trypanosoma Sleeping sickness
Ciliated Numerous cilia Paramoecium -
Sporozoans Infectious spores Plasmodium Malaria

Important NCERT Diagrams

  • Diatoms (various shapes)
  • Euglena structure
  • Paramoecium with cilia
  • Plasmodium life cycle

🌎 Ecological Importance (NCERT)

  • Primary producers in aquatic ecosystems (phytoplankton)
  • Form base of aquatic food chains
  • Diatoms contribute to 50% of Earth's oxygen production
  • Symbiotic relationships (e.g., zooxanthellae in corals)
  • Diatomaceous earth used in:
    • Filtration systems
    • Polishing materials
    • Natural insecticide
  • Harmful effects:
    • Red tides (Gonyaulax)
    • Parasitic diseases (Malaria, Amoebiasis)

⚠️ Important NCERT Questions

  1. Difference between chrysophytes and dinoflagellates
  2. Why are diatoms used in filtration?
  3. Draw labeled diagram of Euglena
  4. Different forms of protozoans with examples

Prepared according to NCERT Class 11 Biology Chapter 2: Biological Classification