IB Biology SL · 2025
Unit 3: Interaction and interdependence
93 past paper questions from 12 papers across 3 exam sessions. See what repeats, then practise the same skills with AI marking.
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SL archive · from 2025
Unit 3: Interaction and interdependence
Latest exam session: November 2025
- questions
- 93
- questions
- papers
- 12
- papers
- exam sessions
- 3
- exam sessions
- micro-topics
- 38
Topics in Unit 3: Interaction and interdependence
In syllabus order. The ring is the share of the marks each one carries.
3.1
Enzymes and metabolism
11% of marks16 of the 142 marks across the 12 Biology SL papers analysed (11%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 9 questions
3.2
Cell respiration
15% of marks22 of the 142 marks across the 12 Biology SL papers analysed (15%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 10 questions
3.3
Photosynthesis
4% of marks5 of the 142 marks across the 12 Biology SL papers analysed (4%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 5 questions
3.5
Neural signalling
18% of marks25 of the 142 marks across the 12 Biology SL papers analysed (18%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 18 questions
3.6
Integration of body systems
4% of marks5 of the 142 marks across the 12 Biology SL papers analysed (4%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 5 questions
3.7
Defence against infectious disease
9% of marks13 of the 142 marks across the 12 Biology SL papers analysed (9%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 13 questions
3.8
Populations and communities
15% of marks21 of the 142 marks across the 12 Biology SL papers analysed (15%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 15 questions
3.9
Transfers of energy and matter
25% of marks35 of the 142 marks across the 12 Biology SL papers analysed (25%) were on this topic. A past-paper pattern, not a guarantee for your next paper. · 18 questions
Exam pattern
How often each micro-topic has been examined, year by year. Each label is explained under the grid.
Does it repeat?
Top 4 of 38 micro-topics for the next sitting. Numbers are questions per year.
fewermore
| Micro-topic | 2025 |
|---|---|
| 5Modes of nutrition & autotrophs vs heterotrophs, 2025: 5 questions | |
| 4Neurons & the nervous system, 2025: 4 questions | |
| 4Conduction speed & myelination, 2025: 4 questions | |
| 4Food chains, food webs & trophic levels, 2025: 4 questions |
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Questions on Unit 3: Interaction and interdependence, by exam session
Which papers asked about Unit 3: Interaction and interdependence, and which question numbers. Open a paper to see them highlighted.
November 2025
25 questions across 4 papers
May 2025
39 questions across 6 papers
Specimen 2025
12 questions across 2 papers
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Frequently asked questions
Short answers about this page.
Which Biology SL exam sessions are covered for Unit 3: Interaction and interdependence?
3 exam sessions from 2025, the latest November 2025. Every Paper 1 and 2 in every timezone is read and classified in full, which gives 12 papers in this archive.
Which Unit 3: Interaction and interdependence topic comes up most?
Modes of nutrition & autotrophs vs heterotrophs (3.9.1): in 42% of papers, last seen Nov 25 P2 TZ3. Usually "other", worth about 1 marks in a paper that includes it.
Can I see the original question and mark scheme?
No. The wording belongs to the IB. You get the citation, the marks, the command term and the skill tested, plus our own matched practice questions with worked answers and AI marking.
What do "banker", "due" and "rising" mean?
Banker: examined in at least one sitting in four and still appearing. Due: regular before, but absent for the last two exam sessions. Rising: clearly more common in the last two years. Our classification of real papers, not an IB statistic.
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