General Ecology — High-Yield Review

Highest-Yield Facts by Unit

Unit 1 — Intro and Physical Environment

• Ecology spans organism → population → community → ecosystem → landscape → global scales.
• High yield: Weather is short-term; climate is long-term average weather.
• Hadley cells, the Coriolis effect, and ocean currents distribute heat and drive regional climate.
• Biomes are broad vegetation types shaped mainly by temperature and precipitation.

Unit 2 — Organismal and Evolutionary Ecology

• High yield: Natural selection acts on individuals but evolution changes populations.
• Phenotypic plasticity is not genetic adaptation; only heritable change evolves.
• Endotherms generate metabolic heat; ectotherms rely on environmental heat.
• C4 and CAM photosynthesis reduce photorespiration and conserve water.

Unit 3 — Population Ecology

• Dispersion: clumped, uniform, or random.
• High yield: Exponential growth is density-independent; logistic growth adds carrying capacity (K).
• Survivorship curves: Type I (most survive to old age), Type III (most die young).
• Density-dependent factors (competition, disease) regulate; density-independent factors (weather) do not.

Unit 4 — Species Interactions

• High yield: Competitive exclusion: two species cannot occupy the same niche indefinitely.
• Fundamental niche (potential) vs realized niche (actual with competition).
• Batesian mimicry (harmless mimics toxic) vs Müllerian mimicry (toxic species resemble each other).
• Mutualism is context-dependent, not always beneficial.

Unit 5 — Community Ecology

• Species richness (count) ≠ evenness (relative abundance).
• High yield: Keystone species have effects out of proportion to their abundance.
• Top-down (predator) vs bottom-up (resource) control of food webs.
• Island biogeography: species number balances immigration and extinction; larger, closer islands hold more species.

Unit 6 — Ecosystem Ecology

• High yield: NPP = GPP − respiration; energy flows, nutrients cycle.
• Only ~10% of energy transfers between trophic levels.
• Nitrogen is often the limiting nutrient; humans have doubled nitrogen fixation.

Unit 7 — Landscape and Global Ecology

• Habitat fragmentation reduces patch size and connectivity.
• Greenhouse gases warm the planet; CO₂ also causes ocean acidification.
• Bioaccumulation (in one organism) vs biomagnification (up the food chain).

Unit 8 — Conservation

• Habitat loss is the leading threat to biodiversity.
• High yield: The extinction vortex: small populations → inbreeding + drift → lower fitness → smaller population.
• Protected areas, corridors, and restoration are core strategies.

Comparison Tables

Frequently Confused Concepts

Biome and Climate

Population Growth Models

Species Interactions

Energy Flow vs Nutrient Cycle

Biodiversity Threats and Conservation

Cumulative Self-Check (20 questions)

1. What is the difference between weather and climate?
2. Name the three survivorship curve types and one example each.
3. Write the logistic growth equation and define every term.
4. Distinguish a fundamental niche from a realized niche.
5. What is the competitive exclusion principle?
6. Distinguish Batesian from Müllerian mimicry.
7. What does NPP = GPP − R mean?
8. Why is only ~10% of energy transferred between trophic levels?
9. Which nutrient cycle has no major atmospheric component?
10. What is a keystone species?
11. Distinguish primary from secondary succession.
12. State the core prediction of island biogeography.
13. Distinguish bioaccumulation from biomagnification.
14. Name the three types of dispersion.
15. What is the intermediate disturbance hypothesis?
16. Distinguish density-dependent from density-independent regulation.
17. What is the extinction vortex?
18. Name four categories of ecosystem services.
19. What is a metapopulation?
20. Distinguish r-selection from K-selection.

Answers and Rationales

1. Weather is short-term atmospheric conditions; climate is the long-term average.
2. Type I (humans — most survive to old age); Type II (birds — constant mortality); Type III (oysters — most die young).
3. dN/dt = rN((K−N)/K): N = population size, t = time, r = intrinsic growth rate, K = carrying capacity.
4. Fundamental = potential niche without competition; realized = actual niche under competition.
5. Two species cannot coexist indefinitely on the same limiting resource.
6. Batesian = harmless mimics a toxic model; Müllerian = toxic species resemble each other.
7. Net primary production = gross primary production minus respiration (energy stored as biomass).
8. Energy is lost as heat at each level (second law of thermodynamics).
9. Phosphorus (no gaseous phase; cycles via rock weathering and sedimentation).
10. A species whose impact is large relative to its abundance.
11. Primary = on bare substrate with no soil; secondary = on disturbed soil with a seed bank.
12. Species number balances immigration and extinction; more species on larger, nearer islands.
13. Bioaccumulation = buildup within one organism; biomagnification = increasing concentration up the food chain.
14. Clumped, uniform, random.
15. Intermediate disturbance maximizes diversity (disturbance between too little and too much).
16. Density-dependent factors (competition, disease) scale with population size; density-independent factors (weather) do not.
17. Small population → inbreeding/genetic drift → lower fitness → further decline.
18. Provisioning, regulating, cultural, supporting.
19. A set of local populations connected by occasional dispersal.
20. r-selected: many small offspring, little care; K-selected: few large offspring, high care.

Last-Minute Review

• Climate: Hadley cells + Coriolis → prevailing winds and biomes.
• Population: exponential (J) vs logistic (S); density dependence regulates.
• Interaction: competition (−/−), predation/parasitism (+/−), mutualism (+/+), commensalism (+/0).
• Community: richness vs evenness; keystone species; top-down vs bottom-up; succession.
• Ecosystem: energy flows one-way, nutrients cycle; ~10% rule.
• Global change: greenhouse effect, ocean acidification, bioaccumulation vs biomagnification.
• Conservation: habitat loss is the top threat; corridors, protected areas, restoration; extinction vortex.

Links

• Subject overview
• Topic 1
• Topic 10: Population Growth Models
• Topic 21: Energy Flow
• Topic 27: Conservation