IB Biology HL 3.1.18 Positive phototropism Question Bank
Practise IB Biology HL 3.1.18 by applying positive phototropism concepts to exam-style questions.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Exam points
- identify the relevant biological structure, process or evidence
- apply the correct biological mechanism to the question
- evaluate the result using data, adaptation or ecological reasoning
C3.1.18 (HL)—Positive phototropism question 1
[Maximum number: 4]
Hormones are produced in plants and animals and cause changes in the organism.
Describe the role of the plant hormone auxin in phototropism.
a. phototropism is a growth response to direction of light/differences in light intensity
OR
(positive) phototropism is growth towards the light (source);
b. auxin is produced in the shoot (apical) meristem
OR
auxin promotes cell/stem growth/elongation;
c. auxin (efflux) pumps set up a concentration gradient;
d. auxin is transported to the shaded side (of the stem)/side with lower light intensity;
e. (auxin) changes transcription/gene expression (in stem cells);
f. (auxin) causes more growth/elongation on the shaded part of the stem/shoot tip/meristem;
g. stem/shoot (tip)/coleoptile/plant bends towards the light;
Marking guidance:
Allow points made using annotated diagrams.
4 max
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