Sign in to save

Bookmark this page so you can find it later.

Sign in to save

Bookmark this page so you can find it later.

Population Growth Simulator

Simulate and compare population growth models. Explore exponential (unlimited) growth, logistic (carrying capacity) growth, and Lotka-Volterra predator-prey dynamics with interactive graphs, real-time calculations, and ecological presets.

Parameters

generations

Results

N(t)=N0ertN(t) = N_0 \cdot e^{rt}
N(20)
4034
Doubling Time
2.31 gen
Growth Rate (r)
0.300
Growth Factor (per gen)
1.3499

Exponential Growth Curve

Reference Guide

Exponential Growth

When resources are unlimited, populations grow at a constant rate proportional to their size. This produces a J-shaped curve that accelerates over time.

Growth equation
N(t)=N0ertN(t) = N_0 \cdot e^{rt}
Doubling time
td=ln2rt_d = \frac{\ln 2}{r}

In reality, no population grows exponentially forever. Resource limits, disease, and competition eventually slow growth.

Logistic Growth

Logistic growth accounts for limited resources by introducing a carrying capacity K. Growth slows as the population approaches K, producing an S-shaped (sigmoid) curve.

Differential form
dNdt=rN(1NK)\frac{dN}{dt} = rN\left(1 - \frac{N}{K}\right)
Solution
N(t)=K1+(KN0N0)ertN(t) = \frac{K}{1 + \left(\frac{K - N_0}{N_0}\right) e^{-rt}}

Carrying Capacity and Inflection

The carrying capacity K is the maximum population an environment can sustain indefinitely. At K, birth rate equals death rate and population growth stops.

Fastest growth at K/2
dNdtmax=rK4at N=K2\left.\frac{dN}{dt}\right|_{\max} = \frac{rK}{4} \quad \text{at } N = \frac{K}{2}

The inflection point of the logistic curve occurs at N = K/2. Below K/2, growth is accelerating. Above K/2, growth is decelerating as the population approaches its limit.

Predator-Prey Dynamics

The Lotka-Volterra equations model how predator and prey populations interact. Prey grow naturally but are consumed by predators. Predators depend on prey for reproduction and die without food.

Lotka-Volterra equations
dNdt=αNβNP\frac{dN}{dt} = \alpha N - \beta NP
dPdt=δNPγP\frac{dP}{dt} = \delta NP - \gamma P

The result is oscillating populations. When prey are abundant, predators thrive and increase. As predators grow, prey decline. Fewer prey cause predator decline, allowing prey to recover.

Related Content