Predator–Prey Cycles (Biology)

Lesson notes

Overview

Prey boom feeds predators; predators then crash the prey; the cycle repeats. This topic is rated intermediate and is number 46 of 110 in Biology. Builds on the basics with relationships, methods and trade-offs.

What you are seeing

The panel above shows a living system animated over time. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.

In depth

In some ecosystems, predator and prey populations rise and fall in linked cycles. When prey are plentiful, predators have more food and increase; more predators eat more prey, so prey decline; with less food, the predators decline; and then the prey can recover. The Lotka–Volterra equations, dx/dt = αx − βxy for prey, capture this behaviour. The famous record of lynx and snowshoe hare fur trapped in Canada shows roughly ten-year cycles, though real systems include other factors.

Reading the relationship

The expression "dx/dt = αx − βxy" is a compact summary of the idea. It uses the symbols d, x, t, α, β, y; name what each one stands for before you start. Notice that it contains a ratio, so increasing the denominator makes the result smaller. Then use the sliders to see how changing one quantity changes the others.

A guided exploration

1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.

Try this

Predict the outcome first, then test extreme slider values to find where the pattern changes or breaks.

Common pitfalls

Biological processes are rarely all-or-nothing. Look for the feedback, the timing and the exceptions, rather than learning a single fixed sequence by heart.

How it connects

It builds on “Pollination and Seed Formation”, the topic before it in Biology. Once you are comfortable, continue with “Logistic Population Growth”.

Why it matters

Biology shows how living things are built and how they work, grow, inherit traits and adapt.

Where you might use it

Revising “Predator–Prey Cycles” before a class, exam or certification
Understanding inherited conditions, medicines and how the body responds to disease
Working in farming, conservation and food production, where populations and genes matter
Following news about vaccines, genetic testing and climate effects on wildlife

Frequently asked questions

What is Predator–Prey Cycles?

Prey boom feeds predators; predators then crash the prey; the cycle repeats. It is an intermediate topic in Biology.

How do I use the Predator–Prey Cycles simulation?

The panel at the top shows a living system animated over time. Move the sliders one at a time, then press Space to pause the animation and look closer.

What does the formula mean?

The expression dx/dt = αx − βxy packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.

Who is this topic for?

Builds on the basics with relationships, methods and trade-offs. If the quiz feels hard, reread the lesson notes and try the previous topic first.

What should I learn before this?

Start with “Pollination and Seed Formation”, the previous topic in Biology. Each topic in a subject builds on the ones before it.

How do I track my progress?

Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.