Cell domains

What are you doing? Just checking. Counting. In this candy bag, there are 32 red, 26 blue, 21 green and 20 yellow sweets. Are you sorting candy?

Mmm, why not? We sort everything. Animals. Plants. And cells.

What are you talking about? Cells. There are different kinds. And they are sorted in different ways. Look! -- Cells are the building blocks that form all life, and they are sorted into different categories.

Have a look at this timeline. It starts 5 billion years ago and spans up until present day. Oh, there you are! Hi! About four and a half billion years ago the earth was created.

There was no life then, and the world looked very different from today. About 4 billion years ago, life began to form. The very first organisms were creatures consisting of one single cell. Among the first organisms, there was a group called archaea. They lived, and survived, in very hostile environments.

Today, four billion years later, they are still around, and you find them -- in hostile environments. In salty, dark or hot places, where no plants nor animals manage to survive. For a long time, possibly for billion years, archaea were the only life form that existed on earth, but from archaea a new type of cell evolved, bacteria. These are also still around today - everywhere around us, and within us! Probably, there are as many bacteria within your body as there are body cells!

This is absolutely normal. Bacteria can make us ill if they get into the wrong place in the body, but they are also vital for our health. Archaea and bacteria have in common that they don't have a cell nucleus. They are called prokaryotes. Prokaryote is Greek and means "before the nucleus"ݮ ...

because from those earlier cells yet another kind of cell evolved. This new cell type was larger and had a cell nucleus. We call these eukaryotes. Eukaryotes are still around as single cell organisms. But not only that: Eukaryotic cells also developed an interesting ability: They could merge into multi cellular organisms.

Lots of cells, sometimes trillions of cells, started to co-operate. Large and complex organisms evolved, like blue whales, redwood trees -- and people. Archaea and bacteria don't have this ability to merge into multi cellular organisms. These are always single-celled. -- This is how we classify all the cells in existence on Earth. Archaea.

Bacteria. And Eukaryotes. The Three Domains of cells. Cool. But hey?

I want that red candy domain. No, I want that. Why should you have a larger share? - Because. - Because what? - 'Cause I should. - No, you shouldn't...