Layer 21

Ecology, Networks & Ecosystems

Populations become ecosystems: growth, predator–prey coupling, trophic energy flow and robustness in interaction networks.

interactivemodel assumptions visibleestablished science separated from analogy

Story step: Evolution creates populations with different traits; ecology asks what happens when those populations share resources, predators, partners and finite environments.

1 · Logistic growth

Finite resources turn unconstrained exponential growth into density-dependent growth.

dN/dt = rN(1 − N/K)

growth rate r

carrying capacity K

initial population N₀

2 · Predator–prey cycles

Lotka–Volterra is an idealized two-species model in which prey support predators and predators suppress prey.

prey growth α

encounter β

predator loss γ

conversion δ

preypredator

3 · Energy through trophic levels

Only part of the energy available at one trophic level becomes biomass available to the next.

primary energy

transfer efficiency η

The familiar “10% rule” is only a rough pedagogical average; real ecological efficiencies vary.

4 · Network robustness

Food webs and interaction networks can lose nodes without immediately losing all connectivity—but topology matters.

nodes removed

removal mode

—largest connected component

—remaining edges

—remaining nodes

Scientific boundary: Logistic growth, Lotka–Volterra dynamics, trophic transfer and network connectivity are reduced models. Real ecosystems contain many species, spatial structure, evolutionary change, stochastic forcing and context-specific interactions.