yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Predator prey cycle | Ecology | Khan Academy


3m read
·Nov 11, 2024

What I want to do in this video is think about how different populations that share the same ecosystem can interact with each other and actually provide a feedback loop on each other. There are many cases of this, but the most cited general example is the case when one population wants to eat another population. So you have the predator population that likes to eat the prey; you have predator and prey interactions.

I'm doing the prey in, I guess, a somewhat bloody color, I guess because, well, they're going to be eaten. So let's just think about how these populations could interact. Let me draw a little chart here that you're probably familiar with by now, where we show how a population can change over time. The horizontal axis is time, the vertical axis is population.

Let's just, in our starting point, say that our prey is starting out at a relatively high point. Let's say we're right there in time, and let's say for whatever reason our predator population is relatively low. So what do we think is going to happen here? Well, at this point, with a low density of predators, it's going to be much easier for them to find a meal, and it's going to be much easier for the prey to get caught.

Since it's easier for the predators to find a meal, you could imagine their population starting to increase. But what's going to happen as their population is increasing? Well, it's going to be more likely that the prey is going to get caught. There's going to be more of their hunters around, more of the predators around, so that population is going to start decreasing all the way to a point where if the population of the prey gets low enough, the predators are going to have trouble finding food again.

As their population decreases, what's going to happen to the prey? Well, then there are going to be fewer predators around, so their population might start to increase. I think you see what's happening: the predator and prey can kind of form this cyclic interaction with each other. What I've just drawn is often known as the predator-prey cycle.

I just reasoned through that you could imagine a world where you could have the cycle between predator and prey populations, but you can also run computer simulations that will show this, and even observational data out in the field also shows this. One of the often-cited examples is the interactions between the snowshoe hare, which would be the prey in this situation, and the Canadian lynx, which would be the predator in this situation. You see a very similar cycle to what I just drew, reasoning through it.

This right here is actual data. You see the passage of time here, and this is a long passage of time. We're starting in the early 1800s, going all the way to the early-mid 1900s, so it's roughly 100 years of data that we're showing. In the vertical axis, you have thousands of animals, and we're plotting both the population of snowshoe hares and Canadian lynx in a certain area on this chart.

As you see, when the prey population is high, when the predator population is high, when we have a lot of the Canadian lynx around, we see a lower population of the prey, of the hare. But then, since you have a low population of food in this situation, the predator population starts to decrease. Let me draw an arrow here: the predator population starts to decrease.

As that predator population decreases, the prey population increases. You see there's less folks around to hunt them, so the prey population increases. You see that the other way around: when the prey population is really high and the predator population is relatively low, the predators say, "Hey, it's really easy for us to find meals right now."

That was kind of that starting point when I was reasoning through it. Their population starts to increase, and as the predator population increases, the prey population is going to decrease. This is real data showing the snowshoe hare, the prey, and the Canadian lynx, the predator, over many decades to show this predator-prey cycle.

More Articles

View All
Michael Jibson: Playing Myles Standish | Saints & Strangers
Miles Sish was the um military representative on the Mayflower. He went out as a kind of pilgrim as well to find his patch of land, I suppose, in the New World. But he was the military adviser. He was always at the front of the group of people that would …
Analyzing mistakes when finding extrema example 2 | AP Calculus AB | Khan Academy
Aaron was asked to find if f of x is equal to x squared minus 1 to the 2⁄3 power has a relative maximum. This is her solution, and then they give us her steps, and at the end, they say, is Aaron’s work correct? If not, what’s her mistake? So pause this vi…
Being Ethical Is Long-term Greedy
In one of your tweets, you listed out some of the things you should study, like programming, sales, reading, writing, and arithmetic. One of the items that ended up on the cutting room floor was that you should also study ethics. I was originally going to…
BREAKING: The Federal Reserve Pivot (Major Changes Explained)
What’s up, Graham? It’s guys here, and here we go again. After a temporary pause, as of a few hours ago, the Federal Reserve increased their interest rates yet another 25 basis points, bringing us to the highest level that we’ve seen since the peak at the…
Kinetic energy | Physics | Khan Academy
What’s common between your morning hot coffee and a beautiful song coming from a guitar? To answer that question, we need to explore what kinetic energy is, and that’s what we’ll do in this video. But let’s zoom out a little bit. What exactly is energy t…
3 Stoic Ways Of Letting Go
Life can be extremely stressful at times. And this is basically because we’re holding on to illusions of control and because our minds are overthinking and ruminating all the time. In most cases, holding on to things is a waste of energy, and overdoing it…