An important way that we can look at the interrelationship between different organisms is by looking at this thing called a predator-prey relationship. The predator, obviously, is the organism that eats the prey. The prey is the poor thing that gets eaten. Now I want you to see, I want to show you each of the graphs or the traces and we'll see how they're interrelated.
So down here we've got time and this time is usually in years. And here we've got our population or the number. of organisms. So let's start by looking at the prey. So the prey population is going to increase when the conditions are right.
So there's plenty of food and the predator level is low. And so their population increases because of reproduction. And then the population actually peaks.
It peaks because we have an increased number of predators. So if you imagine there's plenty of food and there's a lot of prey. plenty of food for the predators, well their population is going to increase. So as their population increases, the prey population peaks and starts to drop down. When there's less food for the predators, the predator population peaks and drops down.
And then they both continue on with this cycle. They're interrelated. There's a number of things, in fact probably three things I want you to be able to see. First of all they both have have the same pattern of peaks and troughs.
I want you to also see that there's more prey than there is predators. And that's of course because of the inefficiency of the energy transfer through the food chain. The other thing is that the predator graph is delayed behind the prey graph. So it lags behind. Both of these are dependent on each other.
A change in one changes the other. So again, continuing with our idea about the interrelationship and human impact, if we impact on one, we're going to impact on the other as well.