Biology for Dan and Sophie: Part 1 - What is Biology?

What is biology?

Biology is the study of living things. Living things include animals, plants, bacteria and possibly viruses. Rather than having to write that every time, we use the word "organism" to mean all those different types of living things.

What is life?

This is a surprisingly difficult question to answer. You notice I used the word "possibly" when I referred to viruses just now? That's because biologists still haven't decided whether they are alive or not. This may seem crazy but I'll try and show you it isn't. Part of the problem is that there are lots of different types of organisms and definitions that are easy to apply to one organism are really hard to apply to another. 

For example, think of all the things that make you alive. . . 

You hopefully thought of things like you eat, you excrete (I'll let your mum explain what that means!), you move about, you grow and one day you may have babies of your own (in other words you may reproduce). There's three other things you do which are much harder to think of. They are: organisation, homeostatis and adaptation. These are big words so we'll take them one at a time.

Organisation just means that your body is organised. You aren't a bunch of cells all mushed together. Instead you have a brain made of brain cells, a liver made of liver cells, lungs made of lung cells and so on. This is all kept inside you by your skin made of skin cells. 

Homeostatis is a word made from two words. Biologists like to do this a lot as it allows us to say things using one word instead of lots of them. Homeostatis means "to stay the same". What this means is that your insides stay the same even if things outside change. For example, if it's snowing outside and you go outside without putting on your coat, you won't get cold straight away. Your fingers and toes might but you insides - your heart, liver, lungs, stomach and intestines - won't get cold for a very long time. Your body is able to stay warm even if it's cold. This is different to something that's not living. If you took your toys out into the snow they would get cold very quickly.

Adaptation means change. In biology adaptation is very important because its a key part of evolution which I will explain later. 

From all this you can see it's pretty easy to think of lots of ways you are alive. But for some organisms, like viruses, it's much harder. Viruses don't do all these things but they do some of them. This makes some people think they are alive while others disagree depending on how strict they want to be. Deciding when something is alive and when it isn't is very difficult and it is something biologists can argue over a lot!

How did life arrive on Earth?

This is another difficult question. We have found fossils of the earliest cells from 3.5 billion years ago so we know it's been around for a very long time. We think it began on Earth but how it began is still a question biologists are trying to answer. There are several theories but they're a bit too complicated to go into now. One thing to know, though, is that this early life had DNA. DNA is a very important chemical molecule. It is inside every single living organism and it gives instructions on how to develop and grow. It is another key part of evolution so I will explain more about that later.

We don't know if life arose once or many times but if it was many times all the other different ways died long ago. We know this because DNA is the only molecule used to give instructions, from bacteria to humans. We all use DNA. This means we are related to bacteria and every other organism, but this again gets into evolution which I will explain next time.

Summary

Biology is the study of life. Unfortunately we don't entirely know what we mean by "life". We have decided that there are 7 key features living things should have but not everything does all 7 so biologists argue over whether they are alive or not. The 7 features are:

1. eating and excreting (metabolism)

2. growing

3. responding to the environment (moving)

4. having babies (reproducing)

5. homeostasis

6. organisation

7. adaptation

We don't know how or when life began on Earth but it happened a very long time ago. We don't know if it happened once or many times but DNA was the winner and now every living thing uses it.

Next time . . .
Evolution!