HardBiologyHigh School (11–12)Ecology and Environment › Organisms and PopulationsConceptual

In the rocky intertidal region, all the starfish Pisaster were removed from an enclosed area…

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Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

In the rocky intertidal region, all the starfish Pisaster were removed from an enclosed area. What happened to the invertebrate species in a year, and why?

What does this show about the work of a predator?

How was the prickly pear cactus controlled in Australia?

A student says that predators are always bad for the prey species. Give one reason against it.

Need a reminder? The key ideaShow

In predation, the predator gains and the prey is harmed. Predators carry energy, control the prey and keep species diversity. Prey defend with camouflage, poison and warning colours, thorns and chemicals. The balance point of the Lotka-Volterra equations $\dfrac{dx}{dt} = ax - bxy$ and $\dfrac{dy}{dt} = cxy - dy$ is $x = d/c$ and $y = a/b$ , and the swings have the period $2\pi/\sqrt{ad}$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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