 Hello, my name's Jay. In the next few videos we're going to have a look at how cells access energy so that they can do work. So far in this unit you've been looking primarily at plant cells and we're going to look at animal cells next so we need to think about how we classify organisms. Classification is a way of breaking things into groups to be able to understand the characteristics of each of those groups. It depends on what your question is or what you're trying to find out as to how you classify organisms. You could classify them by color, by size, by whether they're multicellular or unicellular or whether they're eukaryotic or prokaryotic. In biology we have a lot of different ways of classifying things and sometimes they will overlap. Another way of classifying organisms is through how do they get their energy. So how do you get your energy? If you had some cereal for breakfast you might have got your energy for today through your cereal. Where did that cereal get its energy? Cereal was once part of a plant growing in a field and the plant would have got its energy from the sun. You probably also had milk on your cereal and you can get energy from milk as well. Where did the milk get its energy? The milk came from a cow. The cow got its energy from the grass. The grass got its energy from the sun. So we can classify organisms through where they get their energy. There are those that make it themselves using sunlight and there are those that eat other organisms or take in other organisms. So we call these two groups autotrophs and heterotrophs. Auto means self. Trofe sounds like trophy but it actually means nourishment or food so imagine winning a treat and hetero means other. So rely on themselves to get nourishment and rely on eating other things to get nourishment. Okay we can classify now our little scene by who's an autotroph and who's an heterotroph. So we're just going to classify the living organisms. Our person eats the cereal, they're a heterotroph. The cereal growing in a field got its energy from the sun. It's an autotroph. The cow eats the grass to get energy so it's a heterotroph and the grass gets its energy from the sun so it's an autotroph. We didn't have any smaller organisms in our scene. Some bacteria are autotrophs, fungi are heterotrophs and some bacteria are heterotrophs as well.