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NEET (UG) · revision cheat sheet · neetlogic.in
Botany
17 chapters · 45 topics · ~180 marks · 33 solved previous-year questions
Class 11
1. The Living World
- Characteristics of living organisms —
- Growth, reproduction and metabolism all have exceptions — mules and sterile worker bees are alive but never reproduce — so NCERT treats consciousness, the ability to sense and respond to the environment, as the one property that defines life without exception. Watch for options that call reproduction a universal criterion of a living organism.
- Taxonomy, nomenclature and taxonomic categories —
- The rank between kingdom and class is named differently by convention — phylum for animals, division for plants — and NEET tests this exact word swap more often than the rest of the hierarchy combined. Keep taxon (an actual group, e.g. Insecta) distinct from category (the rank itself, e.g. Class).
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2. Biological Classification
- Five-kingdom classification —
- Whittaker's five kingdoms are separated on five criteria — cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships — and mode of respiration is not one of them, though options often slip it in. Viruses, viroids and lichens are deliberately left out of all five kingdoms because they don't fit a cellular definition of life.
- Monera, Protista and Fungi —
- Match fungal class to its sexual spore, not just to a genus name: zygospores or oospores in Phycomycetes, ascospores in an ascus for Ascomycetes, basidiospores on a basidium for Basidiomycetes — and Deuteromycetes are grouped separately for exactly one reason, that no sexual stage is known for them at all.
- Viruses, viroids and lichens —
- The one fact worth knowing cold: a viroid is infectious RNA with no protein coat at all, unlike a virus, which always packages its nucleic acid inside a protein capsid — that missing coat is the whole reason Diener's discovery was notable, and it's the detail options most often drop or reverse.
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3. Plant Kingdom
- Algae —
- NEET draws heavily on one table — Chlorophyceae stores true starch, Phaeophyceae stores it as laminarin or mannitol, Rhodophyceae as floridean starch, each with its own matching pigment set — and wrong options routinely swap the storage product or pigment between two of the three classes.
- Bryophytes and pteridophytes —
- One distinction organises this whole comparison: the gametophyte is the dominant, independent generation in bryophytes, while in pteridophytes the sporophyte is dominant and independent and the gametophyte (prothallus) is reduced to a small, short-lived stage.
- Gymnosperms and angiosperms; alternation of generations —
- The gymnosperm fact NEET returns to again and again: their endosperm forms before fertilisation, as part of the haploid female gametophyte — the opposite of angiosperms, where the endosperm is triploid precisely because it is a product of fertilisation itself, via triple fusion.
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4. Morphology of Flowering Plants
- Root, stem and leaf: modifications —
- The classic mix-up is thorn versus spine: a thorn (Bougainvillea, Citrus) is a hardened, axillary branch — a stem structure — while a spine (Opuntia, Acacia) is a modified leaf or stipule, and NEET relies on their shared "sharp defensive structure" look to test whether you actually know the difference in origin.
- Inflorescence, flower and floral formula —
- Whether the main axis keeps growing decides everything: a racemose inflorescence has an indefinite, still-growing axis and opens acropetally (oldest flower at the base), while a cymose one ends in a terminal flower that stops the axis, so it opens basipetally instead — options frequently swap which order goes with which type.
- Fruit and seed; families —
- Not every fruit is simply "a ripened ovary": apple, pear and cashew are false fruits whose fleshy, edible part develops from the thalamus (receptacle) rather than the ovary, which is exactly the example set NEET uses to check this distinction.
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5. Anatomy of Flowering Plants
- Tissues and tissue systems —
- Living versus dead at maturity is the axis NEET tests: collenchyma stays alive and can keep dividing, giving flexible support to organs still growing, while sclerenchyma is dead and uniformly lignified, giving rigid support wherever growth has already stopped — options like to swap "living" and "dead" between the two.
- Anatomy of dicot and monocot root, stem, leaf —
- The anatomical fact that predicts almost everything else asked here: dicot stems have open vascular bundles (cambium present, so secondary growth is possible) arranged in a ring, while monocot stems have closed bundles (no cambium, no secondary growth) scattered through the ground tissue.
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6. Cell: The Unit of Life
- Cell theory, prokaryotic and eukaryotic cells —
- "No membrane-bound organelles" does not mean "no ribosomes" — prokaryotic cells still have 70S ribosomes, since a ribosome is never membrane-bound to begin with; what prokaryotes actually lack is the endomembrane system and DNA-containing double-membrane organelles.
- Cell membrane, cell wall and endomembrane system —
- Keep wall and membrane separated by function, not just position: the cell wall is freely (fully) permeable and never itself controls what enters or leaves, while it's the plasma membrane underneath that is selectively permeable — crediting the wall with selective transport is the standard trap.
- Mitochondria, plastids, ribosomes, cytoskeleton, nucleus —
- Mitochondria and plastids are the two organelles carrying their own circular DNA and their own 70S ribosomes — the same size class as a bacterial ribosome, not the 80S kind on the rest of the eukaryotic cell's machinery — which is exactly the evidence the endosymbiotic theory is built on.
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7. Cell Cycle and Cell Division
- Phases of the cell cycle —
- S phase doubles the DNA content but not the chromosome number — each chromosome simply gains a second sister chromatid, so the count only changes once anaphase splits the centromeres. Resist calling G1 and G2 empty "gaps": both are long, active periods of growth and synthesis, not pauses.
- Mitosis —
- Mitosis isn't restricted to diploid cells the way meiosis is — plenty of haploid cells, in fungi, algae and gametophyte tissue, divide mitotically too, since mitosis only has to copy whatever chromosome number is already present, never halve it.
- Meiosis and its significance —
- Only meiosis I actually reduces the chromosome number, by separating homologous pairs; meiosis II is mechanically just mitosis run on haploid cells, separating sister chromatids without reducing anything further. Treating both divisions as equally "reductional" is the recurring error.
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8. Photosynthesis in Higher Plants
- Light reaction: photosystems, electron transport, photophosphorylation —
- Cyclic photophosphorylation runs on Photosystem I alone, cycling electrons back to the same photosystem — so it produces ATP only, with no NADPH and no oxygen evolved, since splitting water is strictly a Photosystem II job.
- Calvin cycle, C4 pathway, photorespiration —
- C4 plants don't skip the Calvin cycle — they still run it, just relocated to the bundle sheath cells, after PEP carboxylase in the mesophyll (which cannot bind oxygen) concentrates CO2 there and starves RuBisCO of the oxygen that would otherwise trigger photorespiration.
- Factors affecting photosynthesis —
- Blackman's law of limiting factors is the lens for every graph question here: the factor nearest its minimum sets the rate, so a light-saturation plateau means light has stopped being limiting and something else — usually CO2 or temperature — now is, not that photosynthesis has maxed out for good.
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| List I | List II |
|---|---|
| A. Chlorophyll a | I. Yellow-green |
| B. Chlorophyll b | II. Yellow |
| C. Xanthophylls | III. Blue-green |
| D. Carotenoids | IV. Yellow to yellow-orange |
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9. Respiration in Plants
- Glycolysis and fermentation —
- Glycolysis happens in the cytoplasm, not the mitochondrion, and runs identically whether the cell goes on to respire aerobically or ferment. Fermentation itself adds no extra ATP beyond glycolysis's own net 2 — its only job is regenerating NAD+ so glycolysis can keep going.
- Krebs cycle and electron transport chain —
- FADH2 hands its electrons to the transport chain at Complex II, skipping Complex I entirely — which is exactly why it yields fewer ATP than NADH (2 versus 3, in the standard accounting) even though both are reduced coenzymes generated by the same turn of the cycle.
- Respiratory quotient and amphibolic pathway —
- RQ reveals what's being burned: carbohydrate respiration gives RQ = 1, fat gives RQ below 1 (oxidising its extra hydrogen needs more O2 than the CO2 released), and organic acids give RQ above 1. Respiration is also amphibolic, not purely catabolic — its intermediates are routinely drawn off to build fats and amino acids too.
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10. Plant Growth and Development
- Phases of growth and differentiation —
- Growth plotted against time gives a sigmoid curve, not a straight line — a slow lag phase, a rapid exponential phase, then a stationary phase as the growth rate itself declines — and NEET's graph questions usually just want the segment named correctly.
- Plant growth regulators: auxin, gibberellin, cytokinin, ethylene, ABA —
- Auxin's apical dominance is a genuine paradox worth remembering: the same hormone that drives elongation at the shoot apex simultaneously suppresses the lateral buds below it, so it's removing the apex — not adding more auxin — that finally lets the laterals grow.
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Class 12
11. Sexual Reproduction in Flowering Plants
- Flower structure, microsporogenesis and megasporogenesis —
- Microsporogenesis and megasporogenesis are not symmetric: meiosis in the microspore mother cell gives four functional pollen grains, but meiosis in the megaspore mother cell gives four megaspores of which normally only one — usually the chalazal one — survives to form the embryo sac.
- Pollination and double fertilisation —
- "Triple fusion" names one single fusion event involving three haploid nuclei — one male gamete plus both polar nuclei — not three separate fusions, and it's this event, not syngamy, that produces the triploid primary endosperm nucleus.
- Post-fertilisation: embryo, seed, fruit; apomixis —
- Apomixis produces a seed without any fertilisation at all, often by a nucellar cell developing directly into an embryo — and it matters commercially because it would let a hybrid variety breed true, passing on its hybrid vigour indefinitely instead of segregating out in the very next generation.
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12. Principles of Inheritance and Variation
- Mendel's laws and deviations —
- Don't let "both parental traits show up" collapse into "blended appearance": incomplete dominance genuinely blends into an intermediate phenotype (pink Mirabilis), while codominance keeps both parental phenotypes fully and separately visible at once (AB blood group) — NEET options trade directly on that difference.
- Chromosomal theory and linkage —
- Genes on the same chromosome recombine less often than the 50% independent assortment would predict, and less often still the closer together they sit — the extreme case NCERT names is male Drosophila, where crossing over does not happen at all.
- Sex determination, mutation, genetic disorders —
- Don't default to the mammalian pattern: in the ZW system that governs birds (and some fish and moths), it's the female who is heterogametic and determines the offspring's sex — the reverse of the XY system, where that role belongs to the human male.
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13. Molecular Basis of Inheritance
- DNA structure and replication —
- Meselson and Stahl's density-gradient experiment on E. coli, tracking 15N and 14N through generations, is the direct proof that replication is semiconservative — each new DNA molecule keeps exactly one parental strand — and NEET likes to ask which generation produces which density band.
- Transcription, genetic code, translation —
- The genetic code is degenerate — most amino acids answer to more than one codon — but not evenly: methionine (AUG) and tryptophan (UGG) are the two exceptions with only a single codon each, which is exactly why AUG can double as both the start signal and an amino-acid codon without ambiguity.
- Gene regulation: lac operon; Human Genome Project, DNA fingerprinting —
- The lac operon is off by default — the repressor sits on the operator and blocks transcription — and lactose itself (as allolactose) is the inducer that removes the repressor, switching on one polycistronic mRNA for all three structural genes at once, unlike any eukaryotic gene.
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| List I | List II |
|---|---|
| A. Alfred Hershey and Martha Chase | I. Streptococcus pneumoniae |
| B. Euchromatin | II. Densely packed and dark-stained |
| C. Frederick Griffith | III. Loosely packed and light-stained |
| D. Heterochromatin | IV. Confirmation of DNA as genetic material |
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14. Microbes in Human Welfare
- Microbes in household and industrial products —
- Beyond curd and bread, know the mechanism behind at least one product: statins from Monascus purpureus lower blood cholesterol by competitively inhibiting the enzyme that synthesises it — the kind of specific, mechanistic fact NEET prefers over a bare organism-product pairing.
- Sewage treatment, biogas, biocontrol and biofertilisers —
- Higher BOD means more polluted water, not cleaner — it measures how much oxygen bacteria would consume breaking down the organic matter present, so secondary (biological) treatment exists specifically to bring that number down before effluent is released.
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15. Organisms and Populations
- Organism and its environment; adaptations —
- Regulation isn't always physiological: plenty of conformers — reptiles, most famously — keep their body temperature workable purely through behaviour, basking in the sun or retreating to shade, without ever regulating internally the way a true homeotherm does.
- Population attributes, growth models and interactions —
- Exponential growth (dN/dt = rN) describes a population with no resource ceiling and produces an ever-steepening J-shaped curve that no real population sustains for long; logistic growth (dN/dt = rN(K-N)/K) is the realistic, resource-limited S-shaped curve NEET actually expects you to identify.
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16. Ecosystem
- Structure, productivity and decomposition —
- Net primary productivity is what's left after the plant's own respiration is subtracted from gross primary productivity — and it's this leftover, not GPP, that is actually available as food to every heterotroph in the ecosystem.
- Energy flow, ecological pyramids —
- Pyramids of numbers and biomass can both turn upside down — a single large tree supporting swarms of insects, for instance — but the pyramid of energy cannot: every trophic transfer loses energy as heat, so it stays upright without exception.
- Nutrient cycling —
- Sort each cycle by where its reservoir sits: carbon, nitrogen and oxygen are gaseous cycles with the atmosphere as reservoir, while phosphorus and sulphur are sedimentary, drawing from the earth's crust — phosphorus in particular has essentially no gaseous phase at all, unlike the other three.
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17. Biodiversity and Conservation
- Levels and patterns of biodiversity —
- The species-area slope isn't a fixed number: within a region it comes out to roughly 0.1-0.2 fairly regardless of the taxonomic group studied, but measured across whole continents that same slope steepens sharply to somewhere between 0.6 and 1.2.
- Loss of biodiversity and its conservation —
- Of the "Evil Quartet," habitat loss and fragmentation is the single largest driver of biodiversity loss, ahead of over-exploitation, invasive species and co-extinction — and a region only counts as a biodiversity hotspot when it combines high endemism with being under serious threat, not richness alone.
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| List I | List II |
|---|---|
| A. The Evil Quartet | I. Cryopreservation |
| B. Ex-situ conservation | II. Alien species invasion |
| C. Lantana camara | III. Causes of biodiversity losses |
| D. Dodo | IV. Extinction |
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