Food webs
A food web represents feeding relationships among many species. It extends the idea of a single predator–prey pair to an interacting ecological network.
Network representation
Species can be represented as nodes and feeding relationships as directed links. The network structure identifies which populations can directly affect one another through consumption.
Dynamical representation
If \(N_i(t)\) denotes the abundance of species \(i\), a general model can be written
\[\frac{dN_i}{dt}=F_i(N_1,N_2,\ldots,N_m),\qquad i=1,\ldots,m.\]Each function \(F_i\) contains the relevant growth, mortality and interaction terms for that species.
Indirect effects
Food webs can produce effects that are not obvious from a single pair of species. Changing one population may influence another through chains of interactions, producing trophic cascades.
Key idea. Food-web models combine network structure with population dynamics to study direct and indirect ecological interactions among multiple species.