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Only a third of the human body is made of solid material, the rest is water. Blood and body fluids make up about 45 litres of water in the average adult. Every day we lose water through sweat, urine and from our breath.
This clip is from:
First broadcast:
26 October 2007

Classroom Ideas

Ask students to explain the importance of maintaining water balance for a body to function efficiently. It is worth considering the different roles of water in the body and therefore the effect on cells, organs and systems if water is lacking. Discuss with the class how water balance is an example of homeostasis. Students could carry out a card sort that places the biological actions that respond to a lack or build-up of water.