NEET UG 2027 | Biology | Biological Classification | Chapter 2 NCERT Notes + MCQs

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_Class 11 Biology | NCERT + PYQ Hotspots | 3-4Q Fix Aate Hain_  

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### *1. Systems of Classification*  

1. *Two Kingdom*: Linnaeus. Plantae & Animalia. _Problem_: Bacteria, Fungi, Euglena not fitted.  

2. *Five Kingdom*: R.H. Whittaker 1969. Basis = Cell structure, Thallus org, Mode of nutrition, Reproduction, Phylogenetic relationships.

**Kingdom** **Cell Type** **Cell Wall** **Nutrition** **Body Org** **Examples**

**Monera** Prokaryotic Peptidoglycan Auto/Hetero Unicellular Bacteria, Cyanobacteria

**Protista** Eukaryotic Present in some Auto/Hetero Unicellular Amoeba, Paramecium, Euglena

**Fungi** Eukaryotic Chitin Heterotrophic, Absorptive Multicellular, Loose tissue Yeast, Mushroom, Penicillium

**Plantae** Eukaryotic Cellulose Autotrophic Tissue/Organ Algae, Moss, Fern, Trees

**Animalia** Eukaryotic Absent Heterotrophic, Holozoic Organ/Organ system Sponge to Human

### *2. Kingdom Monera* `Most Important for NEET`  

- *Bacteria*: Sole members. Most abundant microorganisms.  

- *Shapes*: Coccus = Spherical, Bacillus = Rod, Vibrium = Comma, Spirillum = Spiral.  

- *Nutrition Types*:  

    1. *Autotrophs*: Photosynthetic = Cyanobacteria. Chemosynthetic = Nitrosomonas.  

    2. *Heterotrophs*: Most bacteria. Decomposers, Parasites, Symbiotic.  

- *Archaebacteria*: Live in harsh habitats.  

    1. *Halophiles* = Salty areas. 2. *Thermoacidophiles* = Hot springs. 3. *Methanogens* = Marshy areas, guts of ruminants. Produce CH₄.  

    2. *NEET Gold*: Different cell wall structure than other bacteria. Survive extreme conditions.  

- *Eubacteria*: True bacteria. Have rigid cell wall + flagellum if motile.  

- *Cyanobacteria*: BGA. Photosynthetic. Have chlorophyll a. Impound water blooms. Fix N₂. Ex: _Nostoc_, _Anabaena_. Heterocyst for N₂ fixation.  

- *Mycoplasma*: Smallest living cell. No cell wall. Can survive without O₂. Pathogenic.  

- *Reproduction*: Binary fission, Spore, Sexual = Conjugation, Transformation, Transduction.  

### *3. Kingdom Protista*  

- *Chrysophytes*: Diatoms & Golden algae. Cell wall = Silica = Indestructible. Forms diatomaceous earth. Chief producers in oceans.  

- *Dinoflagellates*: Marine, Photosynthetic. Cellulose plates on wall. 2 flagella. _Gonyaulax_ = Red tides. Toxins kill marine fish.  

- *Euglenoids*: _Euglena_. Fresh water. No cell wall, protein rich pellicle. 2 flagella. Mixotrophic = Photosynthetic in light, heterotrophic in dark.  

- *Slime Moulds*: Saprophytic protists. Body = Plasmodium. Spores with true walls. Extremely resistant.  

- *Protozoans*: Primitive animals.  

    1. *Amoeboid*: _Amoeba_, _Entamoeba_ = Parasite. Pseudopodia.  

    2. *Flagellated*: _Trypanosoma_ = Sleeping sickness.  

    3. *Ciliated*: _Paramecium_. Gullet, cilia, coordinated movement.  

    4. *Sporozoans*: _Plasmodium_ = Malaria. Infectious spore-like stage.  

### *4. Kingdom Fungi* `2Q Pakka`  

- *Features*: Eukaryotic, Heterotrophic, Absorptive. Cell wall = Chitin. Body = Mycelium = Network of hyphae.  

- *Nutrition*: Saprophytes, Parasites, Symbionts = Lichen & Mycorrhiza.  

- *Reproduction*:  

    1. *Vegetative*: Fragmentation, Fission, Budding.  

    2. *Asexual*: Conidia = _Penicillium_, Sporangiospores = _Mucor_, Zoospores.  

    3. *Sexual*: Plasmogamy → Karyogamy → Meiosis. Dikaryophase = n+n in Ascomycetes & Basidiomycetes.  

*Classes of Fungi*:

**Class** **Mycelium** **Spore** **Example** **NEET Point**

**Phycomycetes** Aseptate, Coenocytic Zoospore, Zygospore *Mucor*, *Rhizopus*, *Albugo* Algal fungi. Bread mould

**Ascomycetes** Septate Conidia, Ascospores in ascus *Penicillium*, *Aspergillus*, *Yeast*, *Morels*, *Truffles* Sac fungi. Yeast = Unicellular. Edible

**Basidiomycetes** Septate, Dikaryotic Basidiospores on basidium *Agaricus* = Mushroom, *Puccinia* = Rust, *Ustilago* = Smut Club fungi. Best decomposers

**Deuteromycetes** Septate Only asexual = Conidia *Alternaria*, *Colletotrichum*, *Trichoderma* Imperfect fungi. No sexual stage known

### *5. Viruses, Viroids, Prions, Lichens* `1Q Pakka`  

1. *Viruses*: Non-cellular. Obligate parasites. Nucleoprotein. Inert outside host.  

      - *D.J. Ivanowsky*: TMV. *M.W. Beijerinek*: _Contagium vivum fluidum_. *W.M. Stanley*: Crystallised virus.  

      - *Structure*: Protein coat = Capsid. Genetic material = DNA or RNA, never both. Plant virus = ssRNA. Animal virus = dsDNA or ssRNA or dsRNA. Bacteriophage = dsDNA.  

2. *Viroids*: T.O. Diener 1971. Free RNA without protein coat. Smaller than virus. Potato spindle tuber disease.  

3. *Prions*: Proteinaceous infectious particles. No nucleic acid. Cause mad cow disease = BSE, Creutzfeldt-Jakob disease.  

4. *Lichens*: Symbiosis of Algae + Fungi. Algae = Phycobiont = Autotrophic. Fungi = Mycobiont = Water, minerals, shelter.  

      - *NEET Gold*: Pollution indicators. Do not grow in SO₂ polluted areas.  

### *6. Last 5 Year PYQ One Liners* `Ratta Maar Le`  

1. *Methanogens* = Present in guts of ruminants = NEET 2024.  

2. *Diatomaceous Earth* = Cell wall deposits of diatoms = Used in polishing, filtration = NEET 2023.  

3. *Red Tide* = _Gonyaulax_ dinoflagellate = NEET 2022.  

4. *Dikaryophase* = Occurs in Ascomycetes & Basidiomycetes = NEET 2021, 2019.  

5. *Chitin Cell Wall* = Fungi = NEET 2020.  

6. *Mycoplasma* = Smallest cell, no cell wall, pathogenic = NEET 2023.  

7. *Cyanobacteria* = _Nostoc_, _Anabaena_ have heterocyst for N₂ fixation = NEET 2022.  

8. *Imperfect Fungi* = Deuteromycetes = Only asexual stage known = NEET 2021.  

9. *Lichen* = Pollution indicator, SO₂ sensitive = NEET 2020, 2018.  

10. *Viroids* = Free RNA, no protein coat = NEET 2019.