All living things in energy. Now this originally comes from the Sun. Producers can take that energy that's from the Sun and convert it into food and store it in their cells and then that energy which is stored in plants can get passed along a food chain. Now a food chain shows what eats what basically. So we don't put the sun in any food chain.
We don't show the sun there because it's not part of the food chain. It's not food. But it's important to realise that the sun is the source of the energy.
Here is a typical food chain. We've got grass, grasshopper, frog and bird. Now, plants convert the sun's energy into food, as we've just said. Therefore, we call the plant the producer because it's producing the energy.
The arrow indicates where the energy is going. So that's what the arrows show in a food chain. It shows the energy flow. Each stage in a food chain is called a trophic level.
So there are four trophic levels in this food chain. And each trophic level has a particular name. We talked about the producer, then you've got the primary consumer, because the first consumer consumes the grass.
You've got the secondary consumer, and then you have the tertiary consumer. Because it's the last thing in the food chain, we call it the top predator. So in order to build an ecosystem, you're going to need some producers, because otherwise there's no energy in the ecosystem at all.
You're going to need some consumers, because they eat the producers. And then you also need some decomposers, because at some point those producers and consumers are going to die, and that energy needs to be recycled, and those organisms need to be broken down, and it all needs to be cycled round again. So we need bacteria and fungi, because those are decomposers.
And then the other thing you need to form an ecosystem is a physical environment, so all the non-biological components, the water, the soil, the temperature, etc. Here's a typical ecosystem in which there'll be lots of different food chains. We've got the producers, we've got the consumers, but we've also, and we've got the decomposers in there as well, probably in the soil and some living in the water.
But we've also got our abartic factors, the air, the water, the soil, the sunlight. So all these things work together to form an ecosystem. Remember, an ecosystem is a combination of the living organisms and the physical environment. Now, a herbivore is an animal that just eats a plant. In this food chain, the...
Grasshopper is the herbivore. A carnivore is an animal that eats other animals. So in this case it would be a frog and the bird would be carnivores. If you're an omnivore you eat both plants and animals.
Now in reality many food chains overlap with each other. You don't really find just one food chain on its own in the ecosystem. You usually find lots of food chains.
They all usually interrelate with each other to some extent. And animals and plants have different roles within those food chains. And together therefore we call it a food web.
Now food webs can get quite complicated and you need to be able to interpret them and you also need to be able to suggest what would happen if certain organisms died and what the knock-on effects would be. So for example if the sea ducks were removed from this food web then various effects would happen. So for example the bald eagle has to eat more fish which means there is less food for the ospreys and so their numbers may decrease or you could say that there are more bivalves for the herbivorous ducks. and tundra swan to eat and so their numbers may increase so there's a couple of different things and different ways you could look at a food web but you need to be able to say what would probably happen what the knock-on effects would be if an animal became extinct