Botany — Last-Minute Revision
30 must-know Botany points covering all 7 units. Read through this the night before or morning of your TGBIE 1st Year Botany exam.
Five kingdoms: Monera (no nucleus), Protista (unicellular eukaryotes), Fungi (saprophytes), Plantae (autotrophs), Animalia (heterotrophs).
Fungi cell walls contain chitin (not cellulose). They reproduce by spores, are saprophytic or parasitic.
Alternation of generations: gametophyte (n) → sporophyte (2n) → gametophyte (n). In bryophytes, gametophyte is dominant.
Root functions: absorption of water and minerals, anchorage, storage, and sometimes reproduction (adventitious).
Tap root modifications: storage (carrot = conical, turnip = napiform), pneumatophores (breathing roots in mangroves).
Stem modifications: thorns (Citrus), tendrils (grapevine), rhizome (ginger), bulb (onion), corm (colocasia), tuber (potato).
Leaf modifications: spines (cactus = reduced leaves), tendrils (Pisum), phyllodes (Australian acacia), pitchers (Nepenthes).
Inflorescence types: racemose (main axis keeps growing) vs cymose (main axis terminates in flower).
Floral formula: ⊕ = actinomorphic; % = zygomorphic; ♀ = bisexual; ♂ = male. Parts written as K, C, A, G.
Fabaceae: butterfly-shaped flower, 10 stamens (9+1), monocarpellary ovary, fruit = legume. E.g., pea, bean, groundnut.
Solanaceae: actinomorphic, 5 fused petals, 5 epipetalous stamens, bicarpellary superior ovary. E.g., tomato, potato, brinjal.
Liliaceae: actinomorphic, 6 tepals, 6 stamens, 3-loculed superior ovary. E.g., Allium (onion), Aloe, tulip.
Asexual reproduction types: vegetative propagation, budding, fragmentation, spore formation.
Male gametophyte: microsporogenesis → microspore → 2-celled pollen grain (vegetative + generative cell).
Mature embryo sac is 8-nucleate, 7-celled: 3 antipodals + 2 synergids + 1 egg cell + 1 central cell (2 polar nuclei).
Double fertilisation: one male gamete + egg = zygote (2n); other male gamete + polar nuclei = PEN (3n) = endosperm.
Apomixis = seed formation without fertilisation; parthenocarpy = fruit without fertilisation (seedless fruits).
Eukaryotic cell organelles: mitochondria (ATP), chloroplast (photosynthesis), ER (protein/lipid synthesis), Golgi (packaging), lysosome (digestion).
Cell wall: primary wall (cellulose + pectin + hemicellulose); secondary wall (lignin, in wood cells).
Mitosis: PMAT. Prophase = condensation; Metaphase = chromosomes at plate; Anaphase = chromatid separation; Telophase = reformation.
Crossing over occurs at Pachytene stage of Prophase I of Meiosis. It creates genetic variation.
Dicot stem: ring-arranged vascular bundles, open (with cambium). Monocot stem: scattered bundles, closed (no cambium).
Dicot root: tetrarch (4 xylem poles), small pith. Monocot root: polyarch, large pith — contrast is common exam question.
Casparian strip in endodermis: controls movement of water and minerals into the vascular cylinder.
Secondary growth: vascular cambium forms secondary xylem (wood) inward and secondary phloem outward.
Annual rings: formed due to difference in spring wood (large vessels) and autumn wood (small vessels).
Hydrophytes adaptations: aerenchyma (gas-filled cavities for buoyancy), reduced vascular tissue, thin cuticle.
Xerophytes adaptations: sunken stomata, thick cuticle, CAM photosynthesis, water-storing succulent tissue.
Plant succession: bare rock → lichens → mosses → grasses → shrubs → trees (climax community).
Ecological services: oxygen production, carbon fixation, water cycle regulation, soil formation, habitat provision.