Lesson 12: Ecology & Earth Systems

Ecology & Earth Systems Reference

Levels of Ecological Organization

Organism → Population → Community → Ecosystem → Biome → Biosphere

Energy Flow

• Producers: autotrophs; make food via photosynthesis (plants, algae).
• Consumers: heterotrophs; primary (herbivores), secondary, tertiary.
• Decomposers: bacteria and fungi break down dead organic matter, recycling nutrients.
• Only ~10% of energy passes from one trophic level to the next (10% rule).

Biogeochemical Cycles

• Carbon cycle: photosynthesis (CO₂ → organic C), respiration/combustion (organic C → CO₂).
• Nitrogen cycle: N₂ fixation (bacteria), nitrification, denitrification.
• Water cycle: evaporation, condensation, precipitation, runoff, infiltration.

Population Ecology

• Exponential growth: N(t) = N₀ × e^(rt) — unconstrained, J-curve.
• Logistic growth: dN/dt = rN(1 − N/K) — S-curve with carrying capacity K.
• Limiting factors: food, space, predators, disease reduce population.

Climate & Earth Systems

• Greenhouse effect: CO₂, CH₄, H₂O trap heat in atmosphere.
• Earth's layers: crust, mantle, outer core (liquid), inner core (solid).
• Plate tectonics: continents move ~2-10 cm/year; drives earthquakes and volcanism.