NEET Physics: Waves – NCERT Masterclass & 100 MCQ Quiz

BIOLOGICAL CLASSIFICATION

NCERT Masterclass & NEET Biology Study Module

1. Systems of Classification

• Aristotle: Earliest scientific classification. Plants into trees, shrubs, herbs. Animals into those with red blood and those without.
• Two-Kingdom System (Linnaeus): Plantae and Animalia. Did not distinguish between eukaryotes/prokaryotes, unicellular/multicellular, photosynthetic/non-photosynthetic.
• Five-Kingdom System (R.H. Whittaker, 1969): Monera, Protista, Fungi, Plantae, Animalia.

Main criteria used by Whittaker:
Cell structure, Body organization, Mode of nutrition, Reproduction, and Phylogenetic relationships.

2. Kingdom Monera

Bacteria are the sole members. Most abundant micro-organisms. Classified by shape: Coccus (spherical), Bacillus (rod), Vibrio (comma), Spirillum (spiral).

• Archaebacteria: Survive extreme conditions due to different cell wall structure. Halophiles (salty), Thermoacidophiles (hot springs), Methanogens (marshy areas/gut of ruminants, produce biogas).
• Eubacteria (True Bacteria): Rigid cell wall. Cyanobacteria (Blue-green algae) have chlorophyll 'a', fix nitrogen in specialized cells called heterocysts (e.g., Nostoc, Anabaena).
• Mycoplasma: Completely lack a cell wall. Smallest living cells known. Can survive without oxygen. Many are pathogenic.

3. Kingdom Protista

All single-celled eukaryotes. Boundaries of this kingdom are not well defined. Primarily aquatic.

• Chrysophytes: Diatoms & golden algae (Desmids). Cell walls embedded with silica (indestructible). Accumulate to form 'diatomaceous earth'. Chief producers in oceans.
• Dinoflagellates: Mostly marine & photosynthetic. Two flagella. Red dinoflagellates (Gonyaulax) cause red tides and release toxins killing marine fishes.
• Euglenoids: Fresh stagnant water. Protein-rich layer called pellicle instead of cell wall. Connecting link: Photosynthetic in light, heterotrophic in dark.
• Slime Moulds: Saprophytic. Form aggregation called plasmodium under suitable conditions. Under unfavorable conditions, form fruiting bodies with highly resistant spores.
• Protozoans: Heterotrophs (predators/parasites).
  - Amoeboid: Catch prey using pseudopodia (Entamoeba).
  - Flagellated: Cause sleeping sickness (Trypanosoma).
  - Ciliated: Have thousands of cilia, gullet (Paramecium).
  - Sporozoans: Have infectious spore-like stage (Plasmodium - Malaria).

4. Kingdom Fungi

Heterotrophic organisms showing great diversity in morphology and habitat. Body consists of long, thread-like structures called hyphae. Network of hyphae is mycelium. Cell walls made of chitin and polysaccharides.

Sexual Cycle in Fungi:
1. Plasmogamy: Fusion of protoplasms.
2. Karyogamy: Fusion of two nuclei (In Ascomycetes/Basidiomycetes, an intervening dikaryotic stage $n+n$ occurs).
3. Meiosis: In zygote resulting in haploid spores.

• Phycomycetes: Aquatic/decaying wood. Aseptate & coenocytic mycelium. E.g., Mucor, Rhizopus (bread mould), Albugo.
• Ascomycetes (Sac fungi): Mostly multicellular (Penicillium) or unicellular (Yeast). Septate mycelium. Ascospores produced endogenously in asci. E.g., Aspergillus, Claviceps, Neurospora.
• Basidiomycetes (Club fungi): Mushrooms, bracket fungi, puffballs. Mycelium is septate. No asexual spores generally. Basidiospores produced exogenously on basidium. E.g., Agaricus, Ustilago (smut), Puccinia (rust).
• Deuteromycetes (Imperfect fungi): Only asexual/vegetative phases are known. When sexual forms discovered, moved to Ascomycetes or Basidiomycetes. Reproduce by conidia. E.g., Alternaria, Colletotrichum, Trichoderma.

5. Viruses, Viroids, Prions and Lichens

These acellular organisms are NOT included in the five-kingdom classification.

• Viruses: Non-cellular, obligate intracellular parasites. Name virus means venom. Genetic material is either RNA or DNA (never both). Plant viruses usually have ssRNA. Animal viruses have ss/dsRNA or dsDNA. Bacteriophages generally have dsDNA. Protein coat is called capsid made of capsomeres.
• Viroids: Discovered by T.O. Diener (1971). Infectious agents smaller than viruses causing potato spindle tuber disease. Free RNA, lacks protein coat. RNA has low molecular weight.
• Prions: Abnormally folded infectious proteins. Cause BSE (Mad cow disease) in cattle and its human variant CJD. Size similar to viruses.
• Lichens: Symbiotic association between algae (Phycobiont - prepares food) and fungi (Mycobiont - provides shelter/absorbs nutrients). Very good pollution indicators (do not grow in $SO_2$ polluted areas).

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🚀 NEET BIOLOGICAL CLASSIFICATION MEGA QUIZ (100 MCQ)

Solve the 5 parts below to master Monera, Protista, Fungi, and Viruses.

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