Unit 5 Revealing Nature

5 Listen to the podcast and choose the statements that are made.

Jenny: Hello, and welcome to Science Under the Microscope, a science

programme for teens. I'm Jenny.

Josh: And I'm Josh.

Jenny: This week, as part of our series on biodiversity, we are discussing

microorganisms. They are the oldest form of life on Earth. Scientists believe they first

emerged around three and a half billion years ago!

Josh: That's incredible!

Jenny: But you can only see them with a microscope, as these living things are very very small. We're talking about life at the level of the cell. Do you know about cells, Josh?

Josh: Erm... I'm afraid not. What exactly is a cell?

Jenny: Every living thing is made up of cells. They are like bricks that are used to build houses. By the way, most microorganisms are single-celled. This means that they consist of just one cell.

Josh: How strange!

Jenny: Actually, we're the ones who are unusual. The vast majority of life on this planet is made up of single-celled microorganisms. They're everywhere! In the air, in water, there are even microorganisms... inside you. I'm talking about bacteria. Have you heard of bacteria, Josh?

Josh: I have, Jenny. But bacteria, inside me? Yuck!

Jenny: [laughs] That's right. You have lots of them living in your body. In fact, an average human body contains about thirty trillion human cells, and around thirty-nine trillion bacteria cells.

Josh: Seriously? Oh, this is making my stomach turn.

Jenny: Speaking of which, most of the bacteria in your body help with digestion. And they help make the food that goes into your stomach, too. Without bacteria, we wouldn't be able to make cheese, yoghurt, vinegar...

Josh: Really? I didn't know that!

Jenny: Oh, and bacteria are also useful at the other end of the food production process. They have an important role dealing with your waste and that of other organisms.

Josh: Euw! You mean what goes down the toilet?

Jenny: Yes. Bacteria break down this waste and other dead, organic matter, like fallen leaves, into nutrients.

Josh: Oh I get it. And these nutrients go back into the soil where they can be used by plants!

Jenny: That's it exactly.

Josh: All right. Although some of the bacteria may cause diseases in humans, plants and animals, they aren't all bad...