Protists: These are eukaryotic, single-celled organisms.
Modes of Nutrition in Protists:
1. Photosynthetic (Holophytic):
- Organisms are capable of preparing their food from CO2 and water by utilizing sunlight with the help of photosynthetic pigments like chlorophyll via photosynthesis.
- Examples: Dinoflagellates, diatoms, and euglenoids.
2. Holozoic or Zoo-Trophic (Ingestive, Phagotrophic):
- The organism captures and ingests the food like animals.
- Example: Amoeba and Paramecium.
3. Saprobic or Saprotrophic:
- Organism releases enzymes into the surroundings which convert organic matter into simpler products.
- These products are then readily absorbed through the body surface of the organism.
- Example: slime moulds.
4. Parasitic:
- Some protists get their food from the body of other organisms.
- The individual deriving its food is known as a parasite and the organism from which parasite gets food is known as host.
- Example: Trypanosoma, Giardia, Entamoeba.