Biology · 30 min
What does a plant need?
Plan a fair comparison and separate observation from explanation.

01
Take a closer look
Green plants use light energy to build energy-rich substances from water and carbon dioxide. A comparison becomes more informative when we change one condition while keeping the others the same.
02
Now try it
- Plan a comparison of two similar plants under different lighting. Keep water, temperature and observation time as similar as possible.
- Create a table for daily observations. Record measurements separately from assumptions.
03
Think it through
Why should both plants receive the same amount of water?
See a suggested answer
Otherwise a difference might be caused by water rather than light. Keeping conditions the same helps investigate the effect of light.