📌 General Characteristics (NCERT)
- Eukaryotic, mostly aquatic organisms
- Link between plants, animals and fungi
- Reproduction: Both asexual and sexual
- Nutrition: Autotrophic/heterotrophic/mixotrophic
1. Chrysophytes
- Includes: Diatoms (golden algae) and Desmids
- Cell walls with silica (diatoms) - two overlapping shells
- NEET Important: Diatomaceous earth (used in filters, polishing)
- Example: Navicula
2. Dinoflagellates
- Marine, photosynthetic
- Two flagella (longitudinal + transverse)
- Red tides: Gonyaulax bloom
- Example: Bioluminescent Noctiluca
3. Euglenoids
- Freshwater, Pellicle present
- Mixotrophic: Photosynthetic in light, heterotrophic in dark
- Example: Euglena (flagellated)
4. Slime Moulds
- Saprophytic protists
- Form plasmodium (multinucleate mass)
- Example: Physarum
5. Protozoans (Medical Importance)
| Type | Locomotion | Example | Disease |
|---|---|---|---|
| Amoeboid | Pseudopodia | Entamoeba histolytica | Amoebic dysentery |
| Flagellated | Flagella | Trypanosoma | Sleeping sickness |
| Ciliated | Cilia | Paramoecium | - |
| Sporozoans | No locomotion | Plasmodium | Malaria |
💡 NEET Important Points
- Diatoms - chief producers in oceans
- Zooxanthellae (symbiotic dinoflagellates in corals)
- Plasmodium life cycle (NEET favourite)
- Difference between red algae and dinoflagellates
- Economic importance of diatoms
🔬 NCERT Diagrams to Remember
- Diatom structure (pennate and centric forms)
- Euglena with flagellum and eye spot
- Paramoecium with cilia and oral groove
- Plasmodium life cycle stages
⚠️ Common NEET Questions
- Which protist causes red tide? (Gonyaulax)
- Diatom cell wall composition? (Silica)
- Malaria parasite classification? (Sporozoan)
- Which is called connecting link between plants and animals? (Euglena)
NCERT Reference: Class 11 Biology Chapter 2 - Biological Classification
NEET Special: Focus on medical protozoans and economic importance
