5 Must-Know Facts for NEET — Biological Classification

1. Whittaker's 5 Kingdoms (1969): Monera (prokaryotes, peptidoglycan/no wall) → Protista (eukaryotic unicellular: diatoms with silica frustules, Euglena with pellicle, Plasmodium/Trypanosoma) → Fungi (chitin wall, glycogen storage, 4 classes by spore type) → Plantae (cellulose, autotrophic) → Animalia (no wall, holozoic).

2. Virus vs Viroid vs Prion: Virus = DNA OR RNA (never both) + protein capsid (Ivanowsky, 1892); Viroid = naked circular RNA only, no capsid (T.O. Diener, 1971), plant diseases; Prion = misfolded protein, NO nucleic acid (Prusiner, 1982), causes BSE and CJD.

3. Fungi Critical Facts: Cell wall = chitin; energy = glycogen (not starch); Phycomycetes = coenocytic + zygospores (Mucor, Rhizopus); Ascomycetes = ascospores in asci (Saccharomyces, Aspergillus); Basidiomycetes = basidiospores on basidia (Agaricus, Puccinia); Deuteromycetes = conidia only (Alternaria).

4. Monera Key Members: Archaebacteria lack peptidoglycan (methanogens/halophiles/thermoacidophiles); Cyanobacteria (Nostoc, Anabaena) fix $N_{2}$ in heterocysts; Mycoplasma = no cell wall = smallest living cell; Gram +ve = thick peptidoglycan, crystal violet retained; Gram -ve = thin peptidoglycan + LPS, crystal violet lost.

5. Top 5 NEET Traps to Avoid: (i) Viruses contain DNA OR RNA — NEVER both; (ii) Fungi store glycogen NOT starch; (iii) Cyanobacteria are in Monera NOT Protista/Plantae; (iv) Euglena has a pellicle NOT a cellulose cell wall; (v) Archaebacteria LACK peptidoglycan in their cell wall.