Boxi Learn › Biology › Stage 3 · Structure and Evidence
Where does a tree's mass come from?
BIO-3 Matter cycles, energy flowsX-1 Guess, then checkX-2 Evidence outweighs opinion
What many people think
Plants get their food and mass from the soil.
The idea
Most of a plant's dry mass is carbon taken from carbon dioxide in the air by photosynthesis, not from the soil.
Explain it
A friend says 'plants eat soil'. Using the willow numbers, explain where a tree's mass really comes from, and what the soil is still needed for.
Try at home
Grow cress or bean sprouts on wet paper towel, with no soil at all, for a week. They still grow. Where did their new mass come from?