Ecological Principles and Environmental Change Dynamics
ADAPTATIONS
Adaptation = heritable trait ↑ fitness. Types: structural, behavioral, physiological. NS: variation→heritability→differential survival→allele freq change.
Predict adaptations by matching trait to environmental pressure.
DISTRIBUTIONS & NICHES
Patterns: random, uniform, clumped. Determined by dispersal limits, abiotic factors, biotic interactions. Fundamental niche = possible; realized = actual after competition/predation.
POPULATION GROWTH
Exponential: discrete Nt+1=λNt (λ>1 grow), continuous dN/dt=rN (r>0 grow). Logistic: dN/dt=rN(1−N/K). Density dependence slows growth near K.
LIFE TABLES
lx = survivorship; bx = fecundity. R0=Σ(lx bx), R0>1 grow. G=Σ(x lx bx)/R0. R=ln(R0)/G. Uses: stable age structure, conservation.
POPULATION REGULATION
Allee effect: low density→difficulty finding mates/cooperation→growth declines. PVA: extinction risk modeling w/ stochasticity. MVP = minimum stable N.
METAPOPULATIONS
Patches + matrix + dispersal. Big patches, low isolation → high persistence. Fragmentation: colonization–extinction balance.
COMPETITION
Intra vs interspecific. Mechanisms: exploitative (resource use), interference (aggression), apparent (shared predators). Competitive exclusion: identical niches cannot coexist. Coexistence: character displacement, resource partitioning.
PREDATION
Functional responses: I linear, II saturating, III sigmoidal (switching). Paradox of enrichment: ↑ resources → destabilization → cycles/crash.
PARASITISM
Reduces host survival/reproduction. Higher density → more spread. Virulence–transmission trade-off.
MUTUALISM
Both benefit. Mycorrhizae: nutrients↔carbon. Pollination: nectar↔pollination. Can saturate or shift to competition.
COMMUNITY ECOLOGY
Richness (S), evenness, Simpson’s D. Food webs: top-down vs bottom-up. Succession: primary (no soil) vs secondary (soil present). Early r-selected → late K-selected species.
NUTRIENT CYCLING
General flow: uptake→transfer→death→decomposition→mineralization. Decomposition processes: leaching, microbial breakdown, mineralization & immobilization, fragmentation, humus formation. Rates ↑ with warmth/moderate moisture; ↓ when waterlogged. During decay: mass↓, %N↑, C:N↓, lignin↑.
TERRESTRIAL VS AQUATIC
Terrestrial: uptake in soil, decomposition on surface → strong recycling. Aquatic: producers separated from nutrients; mixing needed (turnover).
NATURAL VS AGRICULTURAL
Natural: high nutrient retention. Agriculture: nutrient export→depletion. Solutions: manure, crop rotation, legumes, agroforestry.
NITROGEN CYCLE (5 STEPS)
1 Fixation (N2→NH3/NH4+) bacteria/lightning/industrial.
2 Assimilation (NH4+ or NO3−→organic N) plants→food web.
3 Nitrification (NH4+→NO2−→NO3−) aerobic bacteria.
4 Ammonification (organic N→NH4+) decomposers.
5 Denitrification (NO3−→N2) anaerobic bacteria.
HUMAN N-CYCLE IMPACTS
Haber-Bosch fertilizers, fossil fuel NOx, runoff. Consequences: eutrophication, hypoxia, soil acidification, altered forest health, biodiversity loss.
BIODIVERSITY PATTERNS
Latitudinal gradient: energy, area, evolutionary time. Species–area: S∝A^z (larger → more species). Hotspots: high richness & endemism. Island biogeography:
Large islands ↓ extinction; near islands ↑ immigration.
MAJOR THREATS
Habitat loss, invasive species, pollution, overexploitation, climate change, disease, human population growth.
CONSERVATION
In situ: protected areas, corridors, restoration. Ex situ: zoos, seed banks, breeding. Policy: ESA, CITES. Recovery possible but threats interact synergistically.
THERMAL ECOLOGY — MAIN POINTS
• TPC curve: Tmin → Topt → Tmax
• Ectotherms: rely on environment; use shade/sun/microhabitats
• Endotherms: metabolic heat;
Insulation, shivering, fat
• Q10: metabolism ↑ with temperature
• Acclimation: short-term physiological adjustment
• Heat adaptations: evaporative cooling, behavior, nocturnal shift
• Cold adaptations: torpor, hibernation, countercurrent exchange
• Thermal niche: species persist only in tolerable temp space
• Urban heat island: cities warmer (less canopy, more concrete)
• Microclimates: small temp pockets critical for ectotherms
URBAN ECOLOGY I — MAIN POINTS
• Urban ecosystems = natural + built systems
• Winners: generalists, flexible diet/behavior, disturbance-tolerant
• Losers: specialists, sensitive species, narrow niches
• Urban filters: heat, pollution, noise, fragmentation
• Anole case: brown anoles tolerate heat → dominate urban areas
• Key driver: canopy openness → hotter operative temperatures
URBAN ECOLOGY II — MAIN POINTS
• Traits for urban success: small/medium size, broad diet, boldness
• Urban ants: more queens → survive disturbance
• Nocturnality: reduces conflict w/ humans; creates timing mismatches
• ALAN: disrupts migration, mating, orientation, circadian rhythms
• Outdoor cats: major wildlife mortality (billions of birds/year)
• Bird richness: declines with pavement; increases near riparian zones
• Green infrastructure: improves air, mental health, activity
• Suburban sprawl: fragmented habitat, high resource use
CLIMATE CHANGE I — MAIN POINTS
• Natural forcings: solar variation, volcanoes, Earth’s orbit
• Anthropogenic forcings: CO₂, CH₄, N₂O, land-use change
• Radiative forcing: GHGs trap heat → warming
• Evidence for human cause: GHG measurements, models, isotopes
• Air pollution: CO, SO₂, NOx, ozone, PM → health & ecosystem damage
• Clean Air Act: reduced major pollutants
• RCPs: scenarios of future emissions/warming
• Overall: warming unprecedented → ice loss, sea rise, extreme events
CLIMATE CHANGE II — MAIN POINTS
• Tipping points: irreversible losses (ice sheets, coral reefs, forests)
• CO₂ fertilization: limited by nutrients, heat stress, drought
• Heat waves: mass mortality in wildlife
• Marine heat waves: food web collapse, species shifts
• Range shifts: poleward/uphill movement of species
• Phenology mismatches: plant–pollinator timing fails
• Niche modeling: predicts habitat loss/gain under warming
• Six Americas: public perspectives vary → affects policy
• Ecological impacts: drought, storms, disease spread, extinctions