“Hey, you're taking up the whole bed!”

You're ready to go to sleep, but your wife is already in bed and is stretched out over the whole bed. You need for her to move so that you'll have room to lay down. You say to her:

Hey, you're taking up the whole bed!

Hey!

You say this to get someone's attention. It's especially used in casual situations with a friend when they've done something that's wrong or unfair. In the example above, you say "Hey!" because it's not fair for your wife to take up all the space on the bed.

take up (space)

To "take up" space means to use that space. But "take up" is a slightly negative expression. It's used when space is important, and you don't want the space to be used:

We used to have a piano in the living room, but it just took up a lot of space and no one ever played it.

You can use the word "space" like in this example. Or you can name the space, like in the example at the top or in the following:

That old car is taking up the whole garage.

the whole (something)

"The whole ___" means all of something. You use "the whole ___" when it seems like a lot, or too much. For example:

Did you eat the whole pizza yourself?