Now consider a camel in the desert.

A camel walks across the desert.

It walks for days without a drink.

Then it finds water and drinks a huge amount at once.

The camel needs water. It just goes a long time between drinks.

Now consider a tomato plant in a pot.

Nobody waters it for a week. Its leaves droop and go floppy.

A week with no water: the tomato plant's leaves droop.

Sibyl waters the soil. By the next day, the leaves stand up again.

The next day, with wet soil: the leaves stand up again.

The tomato plant takes in water from the wet soil. It needs water.

Sibyl needs water too. She drinks when she is thirsty.

Four living things, and every one needs water.