Biodiversity and Population Dynamics Lab

Model how local changes scale up to ecosystem-level impacts. Build a claim from data, then revise it after an unexpected disturbance.

Ecosystem Inputs

Ecosystem Scale Habitat Area (km²): 500 Pollution Index: 20% Climate Stress: 15% Invasive Species Pressure: 10% Water Availability: 50% Predation Pressure: 10%

Mathematical Representation

Population model: N_t+1 = N_t + rN_t(1 - N_t/K_W) - ((P + C + I + Pr)/1000)N_t - D N_t

Where: N_t = Current population, N_t+1 = Next population, r = Growth rate, K_W = Carrying capacity, calculated as area × 4 × scale factor × water multiplier × stress penalty, P = Pollution, C = Climate stress, I = Invasive species, Pr = Predation pressure (these four stressors are combined and scaled by 1/1000 in the model), and D = separate disturbance factor applied after other stresses.

Biodiversity index (0-1): B = (Species richness / 100) × habitat quality factor × scale factor

Current Results

Estimated Carrying Capacity (K):

Final Population:

Final Biodiversity Index:

Dominant Risk:

Ecosystem Composition Snapshot (Canvas Model)

Dots represent species populations distributed inside a habitat boundary.

Explain and Revise

Initial explanation (before disturbance): Revised explanation (after disturbance evidence):

Evidence Table

Run	Population	Biodiversity
Baseline	-	-
Disturbance	-	-
Change	-	-

Questions for Understanding

Carrying Capacity and Bottom-Up Factors: How does increasing water availability (a bottom-up factor) change the carrying capacity (K) of the ecosystem? Support your answer with data from the simulation.
Predation and Population Size: Predation is a top-down factor. If you increase predation pressure while keeping all other variables constant, what happens to the final population size? Does the carrying capacity (K) change?
Comparing Risk Factors: Compare the effect of high pollution (80%) vs high predation pressure (80%) on the ecosystem's biodiversity index. Which factor causes a more significant drop in biodiversity and why?
Disturbance Recovery: Run the model with high water availability (100%) and moderate pollution (40%). Trigger a disturbance. Then, run it again with low water availability (10%) and the same pollution level. In which scenario does the population recover better after the disturbance, and what role does water play?
Ecosystem Scale: Set water availability to 20% and predation pressure to 60%. Change the ecosystem scale from Local Wetland to Regional Forest to Global Marine System. How does the scale of the ecosystem influence its resilience to these combined top-down and bottom-up pressures?