High-Yield Traps & Cross-Kingdom Synthesis (revise before the exam)

This set targets the fine distinctions NEET exploits across all five kingdoms and the acellular entities.

Discoverers / firsts: Whittaker - five kingdoms (1969); Ivanowsky - discovered viruses; Beijerinck - Contagium vivum fluidum; Stanley - crystallised viruses (protein); Diener - viroids (1971).

Five-kingdom logic

  • Criteria: cell structure, body organisation, mode of nutrition, reproduction, phylogenetic relationships (NOT 'presence of flagellum').
  • Increasing complexity of body organisation: Monera < Protista < Fungi < Plantae < Animalia.

Cell walls: Monera - non-cellulosic (polysaccharide + amino acids); Fungi - chitin; Plantae - cellulose; Mycoplasma - none; Diatoms - silica; Dinoflagellates - cellulose plates; Euglenoids - none (pellicle).

Monera traps

  • Mycoplasma = smallest living cell, no cell wall - NOT an archaebacterium. Heterocyst (N2 fixation) is a cyanobacterial cell (Nostoc, Anabaena), not archaebacterial. Methanogens produce methane in ruminant gut/marshes.

Protista traps

  • Diatom walls = silica (indestructible -> diatomaceous earth); diatoms are chief ocean producers. Dinoflagellates = cellulose plates, two flagella, red tides (Gonyaulax). Euglenoids = no cell wall, protein pellicle, mixotrophic. Slime moulds = saprophytic, plasmodium, resistant air-dispersed spores.

Fungi traps

  • Coenocytic (aseptate) mycelium = Phycomycetes only; the rest are septate. Basidiomycetes have NO asexual spores; sex organs absent, plasmogamy by fusion of somatic cells -> dikaryon. Sexual cycle order: plasmogamy -> karyogamy -> meiosis. Deuteromycetes = 'imperfect' (only asexual stage known). Sexual spores: Phycomycetes zygospore, Ascomycetes ascospore (endogenous, in asci), Basidiomycetes basidiospore (exogenous).

Acellular entities

  • Virus infective part = nucleic acid, not the protein coat. Plant viruses ssRNA, phages dsDNA; RNA or DNA, never both. Viroid = free RNA, no protein coat (Diener). Prion = protein (BSE/CJD). Lichen = alga (phycobiont, food) + fungus (mycobiont, shelter/minerals).

Assertion-Reason key: (a) Both true, R correct explanation of A; (b) Both true, R NOT the correct explanation; (c) A true, R false; (d) A false, R true.