Question 1

What causes predator-prey cycles in ecosystems?

Accepted Answer

Predator-prey cycles arise from the time-delayed feedback between consumer and resource populations. When prey is abundant, predators multiply rapidly. More predators deplete prey faster than it can reproduce, so prey numbers crash. With less food, predators then starve and decline, allowing prey to recover � starting the cycle again. This is mathematically described by the Lotka-Volterra equations: dN/dt = aN - �NP and dP/dt = dNP - ?P, producing oscillating solutions in phase space.

Question 2

What is carrying capacity?

Accepted Answer

Carrying capacity (K) is the maximum population size an environment can sustain indefinitely, determined by the availability of resources (food, space, water). When populations exceed K, resource depletion and competition increase death rates and reduce birth rates until the population falls back to K. The logistic growth model formalises this: dN/dt = rN(1 - N/K). In the simulator, plant resource grids and maximum-agent limits enforce carrying capacity.

Question 3

What is the Shannon diversity index?

Accepted Answer

The Shannon diversity index H = -S p? ln(p?) measures the information entropy of a community, where p? is the proportion of species i. Higher H means greater diversity. H = 0 when only one species is present; maximum H = ln(S) when all S species are equally abundant. A typical healthy forest scores H � 2�3. The simulator displays live Shannon H, which drops when invasive species crowd out others or when predator-prey oscillations push one species to near-extinction.

Question 4

How do invasive species affect ecosystems?

Accepted Answer

Invasive species disrupt native ecosystems by outcompeting native species for resources, predating on prey with no evolved defences, or altering habitat structure. In the Invasive preset, the introduced rat reproduces very rapidly (repro threshold 45 vs 90 for deer), consuming plant resources faster than they regenerate. This starves native deer, which in turn deprives wolves of food. Shannon diversity collapses as the invasive species dominates � directly observable in the population history chart.

🧪 Ecosystem Simulator – Multi-Species Population Dynamics & Biodiversity

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