Presenter notes: Open with the tallest tree anyone in the room can name or see out of the window. Ask how far it is from the roots to the top leaves. Get an estimate in metres and write it on the board. Then ask the question of the day: that water is in the ground, those leaves are twenty metres up, and the tree has no heart, no pump and no muscle anywhere in it. So what is carrying the water up? Take every answer without judging. Most classes say the roots push it, which is wrong and is exactly the answer you want on the board, because you will come back and cross it out.