AP Biology Unit 8: Ecology — Tips & Strategies

Population Growth Models: Exponential vs. Logistic

concept

Exponential growth (J-curve) occurs with unlimited resources. Logistic growth (S-curve) levels off at carrying capacity (K). Real populations usually follow logistic growth.

Carbon Cycle: Processes That Move Carbon

concept

Photosynthesis removes CO2 from atmosphere. Cellular respiration and combustion return it. Decomposition releases carbon from dead organisms. Fossil fuels store carbon long-term.

Biodiversity: Three Levels and Why It Matters

concept

Biodiversity exists at three levels: genetic diversity (within a species), species diversity (within a community), and ecosystem diversity (variety of ecosystems in a region).

r-Selected vs. K-Selected Species

memorization

r-selected: many small offspring, little parental care, short lifespan (bacteria, insects). K-selected: few large offspring, extensive parental care, long lifespan (elephants, whales).

Energy Flow Through Ecosystems: 10% Rule

concept

Only about 10% of energy is transferred between trophic levels. The rest is lost as heat through cellular respiration. This limits food chain length to 4-5 levels.

Community Interactions: Competition, Predation, Symbiosis

memorization

Interspecific competition (-/-), predation (+/-), mutualism (+/+), commensalism (+/0), parasitism (+/-). Know examples and how each affects population dynamics.