Draw a vertical food chain (part of a food web) showing that sea ...

Question

Draw a vertical food chain (part of a food web) showing that sea urchins eat kelp and that sea otters eat sea urchins. Use this model to (1) show or explain how a trophic cascade works; and (2) offer an explanation for why otters are considered a keystone species.

Accepted Answer

Hi everyone. Welcome back. Here's our next problem. It says how many food chains are linked in the food web? Shown in the following diagram. What you call a food chain is a single chain of starting with a primary producer and then moving up the level the trophic levels of organisms that consume it up to an ultimate consumer. And when we have a food web, like in this diagram here, it shows this interconnectedness that happens in an environment where organisms are existing together, and you might have certain animals being eaten by multiple different consumers, and certain primary producers being eaten by many different consumers as well. So, we have our food web here, and we want to find out how many food chains are shown in this diagram. So, I'm going to scroll down words so we can see our answer choices here. We've got choices of a two, B three, C four and D five. So we're going to expect to find multiple food chains in this diagram. So I'll just come back up here. So let's go ahead and trace these and count how many we get. So I'm gonna start highlighting in blue, we always start with our primary producer and producers, of course, most often our photo synthesizers that harvest the energy from the sun, and then it gets passed up to the animals consuming it. So, we've got only one producer in this food web, which is grass, and I'll start over here highlighting in blue grass consumed by rabbits who get consumed by dogs. So that's dog is our ultimate consumer here, and we're going to call that food chain number one. But now we see that rabbits can be consumed also by foxes. So we've got another food chain going there, that involves um these rabbits. So we say we can have grass consumed by rabbits consumed by foxes with fox as an ultimate consumer. And we'll call that food chain number two. Well, that's all the food chains that the rabbit is involved in. So let's move on over. We see grass is also consumed by rats. So we're gonna trace up from grass and yellow here, grass consumed by rats consumed by owls, with owls as the ultimate consumer. So, I'm gonna call that food chain number three now, that's the only one that rats are involved in. So we'll move on over to another consumer of grass. We're gonna do that one in blue as well. We have grass being consumed by beetles, oops, That grass being consumed by beetles who are consumed by Foxes. So we will call that food chain number four. But we see the beetle also gets consumed by owls. So we'll just trace that one and we have grass consumed by beetles consumed by owls, with owls as ultimate consumer. And we're gonna call that food chain number five. So we've now identified all the different food chains in here. We've got everything highlight every organism highlighted as part of at least one food chain. And we get five different food chains. So that means our answer here is going to be choice D5 as the number of food chains on this particular food web. We'll see you in the next video.

Draw a vertical food chain (part of a food web) showing that sea urchins eat kelp and that sea otters eat sea urchins. Use this model to (1) show or explain how a trophic cascade works; and (2) offer an explanation for why otters are considered a keystone species.

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