Why do we need water?
People drink lots of water. We wouldn't live very long without it! Imagine getting stranded in the desert without water to drink. Humans, and all other living things, need water.
Look carefully at the column graph below. It shows how much water there is in the bodies of some organisms (living things).
Percentage (%) of water in living things
You can see that the living things shown on the column graph are more than 50% water. In fact, some living things are almost entirely made up of water. You can see that jellyfish and tomatoes are approximately 98% water!
1 Which organisms contain the smallest percentage of water?
2 Which organism contains more water than a lobster but less than an earthworm?
Why then do we need water?
When we perspire, the water on our skin evaporates and cools us. And in the body, water surrounds the joints so the bones don't rub together.
Water is also important as a carrier. Blood, which is mainly water, carries nutrients and gases to all parts of the body. Urine, which is mainly water, carries away a waste called urea and other materials that are produced by the body.
Many of the processes which happen inside our bodies, like digestion (the breaking down of food), need water for them to occur.
3 List some of the reasons why living things need water.
