ECO-01 Essential NEET Facts (Bullets)

Temperature is the most ecologically significant abiotic factor — affects enzyme kinetics and metabolic rates
Four organism responses to abiotic stress: Regulate (mammals), Conform (fish/reptiles), Migrate (birds), Suspend (dormancy)
Dormancy types: Hibernation = winter; Aestivation = summer; Diapause = developmental arrest in zooplankton/insects
Population density measured by quadrats (sessile organisms) or mark-recapture (mobile organisms)
r = b − d (intrinsic rate of natural increase = natality − mortality)
Exponential growth equation: dN/dt = rN; integrated form: Nt = $N_{0}$ e^(rt); J-shaped curve
Logistic growth equation: dN/dt = rN(K−N)/K; S-shaped (sigmoid) curve
Carrying capacity (K): maximum sustainable population size in a given environment
Maximum growth rate in logistic model occurs at N = K/2 (inflection point)
(K−N)/K = environmental resistance; approaches zero as N → K
Mutualism (+/+): Rhizobium–legume, mycorrhiza, lichen (algae + fungus)
Competition (−/−): Gause's competitive exclusion principle — two species, one niche, cannot coexist
Predation (+/−): Batesian mimicry = palatable mimics unpalatable; Müllerian = multiple unpalatable converge
Calotropis produces cardiac glycosides as chemical defence against herbivores
Brood parasitism: cuckoo lays eggs in crow nest — parasite benefits, host harmed (+/−)
Commensalism (+/0): orchid on mango tree; cattle egret follows grazing cattle
Amensalism (−/0): Penicillium inhibits Staphylococcus
GPP = total photosynthesis; NPP = GPP − Respiration = energy available to herbivores
Most productive ecosystems: tropical rainforests, coral reefs, estuaries
Decomposition steps (FLCHM): Fragmentation → Leaching → Catabolism → Humification → Mineralization
High lignin content retards decomposition; warm, moist, nitrogen-rich conditions accelerate it
Lindeman's 10% law: ~10% energy transferred per trophic level; ~90% lost as heat
Energy flow is unidirectional — cannot be recycled
Pyramid of energy: ALWAYS upright (no exceptions)
Pyramid of biomass: inverted in aquatic ecosystems (phytoplankton < zooplankton at any given time)
Pyramid of numbers: inverted in tree ecosystems (one tree supports many insects)
Phosphorus cycle has NO gaseous phase — purely sedimentary cycle (unlike carbon and nitrogen)
Carbon cycle: oceans hold 71% of Earth's $CO_{2}$ as dissolved carbon
Primary succession: bare substrate → crustose lichens (pioneer) → mosses → herbs → shrubs → climax forest
Secondary succession: disturbed habitat with soil → faster recovery using existing seed bank
Climax community: stable, self-perpetuating, in equilibrium with environment