Ecology and Population Dynamics: Trophic Levels, Energy Flow, and Carrying Capacity

Producers (autotrophs)

plants, algae → make energy via photosynthesis.

Primary consumers

herbivores.

Secondary consumers

carnivores that eat herbivores.

Tertiary consumers

top predators.

Decomposers

fungi, bacteria recycle nutrients.

Energy flow

Energy flows one way; nutrients cycle.

10% Rule

Only ~10% of energy passes to the next trophic level.

Food chain

single path of energy flow.

Food web

interconnected chains; shows stability.

Biodiversity

More biodiversity = more resilience.

Carrying Capacity (K)

Max population an environment can support long-term.

Limiting factors

Controlled by limiting factors (food, water, space, competition).

Exponential growth

J-curve, unlimited resources.

Logistic growth

S-curve, levels off at carrying capacity.

Density-dependent factors

disease, predation, competition.

Density-independent factors

natural disasters, climate events.

Human Population Dynamics

Growth driven by birth rate, death rate, immigration, emigration.

Demographic transition model

as nations develop, birth & death rates drop.

Resource availability

affects growth (food, water, medicine, jobs).