Question: Is there just one animal at the top of the food web, or is there lots of different ones? Also, if a small species, such as worms, for example, were to die out, would it effect the rest of the food web, and if so, how?

Lydia Bach answered on 9 Nov 2014:

Hi Yoohoo!

That is a really good question to ask, and its what I am researching at the moment.

So it depends where you look. For example in an African Savannah there are maybe three animal species on top of the food web: lions, cheetahs and leopards. In my muddy shores there are only one or two animal species on the top of the food web like the dog fish (coming in at high tide).
Also, there often fewer individual predators than there are individuals of the smaller animals low in the food chain. That is because the predators are often really big and need to eat more to become big. (To gain 1kg of body mass they need to eat 10kg of prey!).

That’s why you are right wondering how extinction of a small species would affect the rest of the food web! For example, if a sea bass only feeds on worms, then sea bass would die out too if all worms would become extinct. But sea bass also feeds on snails and crabs, so we are not sure what happens if worms would die out: Would the bass eat more crabs and snails? What would happen to the snails and worms, could they die out? Would the sea bass grow slower because it doesn’t have the right diet (worms).

You can think about it the other way around too: what would happen if sea bass go extinct and stop predating worms? Would worms increase in numbers and start eating more of their prey?