Life. What is it, how did it begin and how did it take so many diverse forms? Imagine the surface of the primitive earth, the lava flows, the thunder storms sweeping across the surface, the asteroid strikes, no oxygen in the atmosphere, no life - and yet in that primitive situation the very chemicals of life were being created. And so life arose on earth and it went forward. Somehow it also changed the planet and we're part of life. Now we're changing the planet ourselves more than any other life form.

In this series of lectures, we want to explore this together: how it began - as much as we know about that - how it developed into all these different forms, and how that could be. Then explore the rapidly increasing understanding we have of ourselves and how we can alter ourselves, we can fix things. Moving forward into the future, we'll explore how we're going to be able to change things, because we have tremendous knowledge which is growing very fast.

With knowledge comes power, and with power becomes responsibility - and that's where you come in, because there's lots of choices now already about what we should be doing and there's going to be many more in the future. But you're the ones who are going to make those choices. You're the new generation and they're going to be your decisions. So I'm going to ask you during these lectures to give your opinions about how things are, how they should be, what you would like to do with this knowledge. As for me, I've been interested in these questions all my life, and I've been lucky enough to be involved with some of the advances that have happened and recently with this rather extraordinary journey into our very selves - the Human Genome Project.

But let's go back to the beginning, the beginning of life. How did it get going?

Well, we don't really know to be honest, but there are some clues, there are clues inside our own bodies that there were earlier ways of doing things, and there are clues like this experiment that's been reproduced here - the experiment of Stanley Miller and Harold Urey, who created the primitive atmosphere of the earth in model form in such a flask with boiling water, steam from the volcanoes, gases inside those reducing gases, no oxygen but there was methane carbon dioxide, ammonia and hydrogen and sparked. And they found that as this was run week after week, some of the chemicals of life accumulated in the flask. They arose from nothing and also they were coming in from space, these chemicals of life, all the time, like this. Frozen water, balls of ice falling into the earth's atmosphere and things like this, this lovely mineral, carbonaceous chondrite, bringing inside its rocky form carbon atoms from somewhere, arranged in forms again like the chemicals in our own body but we don't exactly know how that happened.

What we do know is that somehow life started and it began to diversify and one of the first things it did to diversify was to start to use sunlight. Use sunlight as energy. It split water, combined it with carbon dioxide and it began to produce oxygen for the first time on earth. And at first the oxygen reacted with the iron in the ocean and it produced lovely banded iron deposits like this one. Layers of rust. If you leave your bicycle out in the rain, well at least if you leave my bicycle out - you'd probably have titanium ones nowadays - but anyway, if you leave my bicycle out in the rain it goes rusty. And it's the same with this: the oxygen and the water in the earth's atmosphere were oxidising the iron that was lying around in the oceans and raining rust down into the floor of the ocean, and that's how these banded deposits came into being. This went on for hundreds of millions of years until the iron was used up and then the oxygen was released into the atmosphere and began to allow breathing creatures to develop, like ourselves but not like so big as ourselves at first, just little things.

This is all very well, it's fine to celebrate life, but what is it, do you actually know what life is? What I want to do is to ask some people to come and help us to decide what life is. Who would like to volunteer? OK you come down, yes, you there. And would you like to come down on the end? Stand behind the desk there… OK, and what are your names?

Natalie. OK, Anna and Natalie, thank you very much. What we're going to do is to bring on some things that are on that trolley and we're going to sort them out into whether they are living or non-living, or - if they're neither of those things - whether they're dead. So let's begin with this. What is this, is this a living thing or a non-living thing? What do you think?

It's a living thing, that's right, so we'll put it in here. Then what about this? What's this? Lump of coal, yes exactly, you don't see so much of this around, my grandmother had a lot of this, but nowadays we sort of have gas and things. Which category would you put it in, Natalie?

Erm ... probably the not-alive category.

You think the not-alive, anybody have any other ideas, yes?

That's right, you see it was living. You're quite right - it's not living, but in our classification here it's dead, because it was once alive. I'm going to pick a flower. It can grow some more, can't it? I put that in there, now what about this, what do you make of that? Anybody?

You think it's dead. Well, yes, it's sort of dying isn't it, now it's been picked. If you're a good botanist you can probably get a little bit of it off and actually grow another plant but for the moment I'm afraid it is dying. Now, what we need is a writer. Can we have a writer please? Now why is that dying and this is living? What's the characteristic thing that's changed? What would you like to say?

Well those flowers have sort of still got food and they're eating food ...

Now what are they doing as a result?

They're growing, yes that's right, Could you write the word 'growing', because that's what this plant's doing. Thanks, great. Now let's go on with something else, whilst she's looking at that. How about this guy? Now this is rather fun. Does anybody know what this is?

It's a crystal, yes. Can anybody guess what sort these are, somebody way up at the back there?

Copper sulphate, excellent. You see how they are growing like one another, do you want to take a little look at that? I think we're agreed crystals are non-living, but the question is exactly why. Slide that gently down to the non-living and let's go onto this one. Now what's this?