To predict a plant response, find the pattern in the evidence, apply it to the new case, and give the reason. A prediction is a claim that the evidence supports.
This lesson follows interpreting plant-hormone investigations in the plant responses chapter.
What is the routine?
- Find the pattern: what changed, and what happened each time?
- Apply it: what is different in the new set-up?
- Predict: state the result in a clear sentence.
- Justify: cite the evidence and the biology.
Worked example: a new set-up
A student grows bean seedlings in a box with a slit that lets light in from the right. The results after three days are:
| Seedling | Treatment | Shoot result |
|---|---|---|
| 1 | No treatment | Bends to the right |
| 2 | Tip covered with foil | Grows straight up |
| 3 | Foil around the stem below the tip, tip uncovered | Bends to the right |
Question. Predict the result if the tip of a fourth seedling is covered with clear plastic instead of foil, and explain. [3 marks]
Find the pattern. Covering the tip with foil stopped the bending, but covering the stem below the tip did not. The tip is the part that detects light.
Apply it. Clear plastic lets light through, so the tip still detects the light.
Predict and justify. The fourth seedling bends to the right, toward the light. Seedling 2 shows bending stops when light cannot reach the tip. Clear plastic does not block light, so auxin still moves to the shaded side and those cells elongate more.
The mistake that costs marks
The common slip is to give a memorised answer that ignores the new detail. Writing “it grows straight because the tip is covered” treats clear plastic as if it were foil.
| Wrong | Right | |
|---|---|---|
| Fourth seedling | Grows straight up | Bends toward the light |
| Reason | Tip covered | The cover is clear, so light still reaches the tip |
| Evidence cited | None | Seedling 2 versus seedling 3 |
Read the material of the cover, not only the word “covered”.
Check yourself
A fifth seedling is placed in the same box, but the foil cover is placed over the stem below the tip and the tip is left uncovered, with the light coming from the left instead. Predict the result.
Answer
The seedling bends to the left, toward the light.
Seedling 3 shows that a covered stem with an uncovered tip still bends, because the tip detects the light. Moving the light to the left moves the shaded side to the right, so auxin gathers there and the right side elongates more.
What to study next
Test the whole chapter with the plant responses practice set. The claim, evidence and explanation revision desk gives you practice at writing predictions with support.
Log each over-confident prediction in the mistake log and paper-error review. For a teacher to go through your predictions, see online one-to-one Biology tuition.