How this analysis was built — please read
New IB Biology syllabus first sat in May 2025. We have 1 real sitting (May 2025) + IBO Specimen papers (2023). To strengthen predictions, we mapped 6 years of old syllabus Paper 1 & Paper 2 data (2019–2024) onto the new 4 themes — core biology content is largely preserved. Old Topics 1–11 map cleanly onto Themes A–D. Old Paper 3 data excluded (tested options which no longer exist). Source labelled on each row: 🟢 New syllabus · 🟡 Mapped old syllabus.
Select your level
Paper 1A — Multiple Choice Questions
🟢 Biology MCQ insight: Biology MCQ tests factual recall, diagram interpretation, and application of concepts. In the old syllabus, Topic 1 (Cell biology) and Topic 3 (Genetics) historically dominated. In the new syllabus, Theme A (Unity & Diversity) and Theme D (Continuity & Change — DNA/Genetics) are expected to carry the most MCQ weight. Every theme appears in every paper — no topic is safe to skip.
Paper 1A MCQ frequency by theme — SL & HL
| IB BIOLOGY — PAPER 1A MCQ TOPIC FREQUENCY | May 2025 + Mapped Old Syllabus 2019–2024 | SL & HL | ||||||||||
| Free preview: Theme A · Themes B–D locked below · 🟢 = new syllabus · 🟡 = mapped old data · HL-only rows greyed in SL view | ||||||||||
| Ref | Theme | Topic / Subtopic | M20 | M21 | M22 | M23 | M24 | M25★ | HL only? | May 2026 |
|---|---|---|---|---|---|---|---|---|---|---|
| THEME A: UNITY & DIVERSITY — cells, classification, viruses, biodiversity (free preview) | ||||||||||
| A.1 | Unity/Div | Cell structure — prokaryotic vs eukaryotic, organelles, ultrastructure, scale & magnification 🟡 | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| A.2 | Unity/Div | Classification & diversity — binomial nomenclature, phylogenetic trees, kingdoms, domains 🟡 | ✔ | — | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐ |
| A.3 | Unity/Div | Viruses — structure, lytic & lysogenic cycles, HIV, COVID, virus-host interactions 🟢 | — | — | — | — | — | ✔★ | SL&HL | ⭐⭐⭐⭐ NEW |
| A.4 | Unity/Div | Conservation of biodiversity — species richness, ecosystem services, threats, conservation strategies 🟡 | ✔ | ✔ | — | ✔ | — | ✔★ | SL&HL | ⭐⭐⭐⭐ |
| A.HL | Unity/Div | Cladistics & gene pools — cladograms, shared derived characteristics, species concepts, speciation HL 🟢 | — | — | — | — | — | ✔★ | HL | ⭐⭐⭐⭐ HL NEW |
★ = confirmed appeared May 2025 · 🟢 new syllabus · 🟡 mapped old syllabus | HL-only rows greyed in SL view
| Ref | Theme | Topic / Subtopic | M20 | M21 | M22 | M23 | M24 | M25★ | HL only? | May 2026 |
|---|---|---|---|---|---|---|---|---|---|---|
| THEME B: FORM & FUNCTION — membranes, proteins, enzymes, cell specialisation | ||||||||||
| B.1 | Form/Func | Membranes & transport — fluid mosaic model, osmosis, active/passive transport, endocytosis | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| B.2 | Form/Func | Proteins — structure (primary to quaternary), enzymes, induced fit, inhibition, denaturation | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| B.3 | Form/Func | Organelles & specialisation — mitochondria, chloroplasts, cell differentiation, stem cells | ✔ | ✔ | — | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ |
| B.4 | Form/Func | Gas exchange & transport — lung structure, haemoglobin, heart, blood vessels, stomata, transpiration | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ |
| B.HL | Form/Func | Chemical signalling — hormones, receptor proteins, signal transduction cascades, gene expression HL | — | — | — | — | — | ✔★ | HL | ⭐⭐⭐⭐ HL NEW |
| THEME C: INTERACTION & INTERDEPENDENCE — ecosystems, homeostasis, immunity | ||||||||||
| C.1 | Interact | Ecosystems — food chains/webs, energy flow, trophic levels, ecological pyramids, succession | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| C.2 | Interact | Cycling of matter — carbon cycle, nitrogen cycle, water cycle, decomposition, global warming | ✔ | ✔ | ✔ | — | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐ |
| C.3 | Interact | Defence & immunity — innate vs adaptive immunity, antibodies, vaccinations, autoimmunity, allergens | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ |
| C.4 | Interact | Homeostasis — thermoregulation, blood glucose (insulin/glucagon), osmoregulation, kidney structure | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| C.HL | Interact | Nervous system & muscle — neurones, synapses, action potential, reflex arcs, muscle contraction HL | — | — | — | — | — | ✔★ | HL | ⭐⭐⭐⭐ HL |
| THEME D: CONTINUITY & CHANGE — DNA, genes, cell division, evolution (most tested overall) | ||||||||||
| D.1 | Continuity | DNA & RNA — structure, complementary base pairing, replication, transcription, translation | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| D.2 | Continuity | Cell division — mitosis stages, meiosis, crossing over, non-disjunction, cancer | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| D.3 | Continuity | Inheritance — Mendelian genetics, dihybrid crosses, sex linkage, codominance, ABO blood groups | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★★ | SL&HL | ⭐⭐⭐⭐⭐ CERTAIN |
| D.4 | Continuity | Natural selection & evolution — Darwin, variation, adaptation, speciation, evidence for evolution | ✔ | ✔ | ✔ | ✔ | ✔ | ✔★ | SL&HL | ⭐⭐⭐⭐⭐ |
| D.HL | Continuity | Epigenetics & gene regulation — methylation, histone modification, lac operon, gene expression control HL | — | — | — | — | — | ✔★ | HL | ⭐⭐⭐⭐ HL NEW |
★★ = heavily tested M25 · ★ = confirmed · 🟡 mapped old · 🟢 new syllabus | HL rows greyed in SL view
🟡 M25 Biology findings: DNA/RNA (D.1), Inheritance genetics (D.3), Membranes/Transport (B.1) and Immunity (C.3) were reported as heavily tested in May 2025. New topics A.3 (Viruses) appeared prominently — as expected for a new syllabus. HL-only additions (Cladistics, Chemical signalling, Epigenetics) all featured in Paper 1A and Paper 2.
🔴 Top 5 Biology MCQ topics — every year
- D.1 DNA & RNA — structure, replication, transcription, translation. Appears in every paper without fail. Know all steps deeply.
- D.3 Inheritance — Mendelian crosses, sex linkage, codominance. Always 3–5 MCQ questions. Know how to draw Punnett squares fast.
- B.1 Membranes — fluid mosaic model, osmosis, transport types. Every year, every level.
- C.4 Homeostasis — blood glucose, thermoregulation, kidney. Always appears with diagrams.
- C.1 Ecosystems — food webs, energy flow, trophic levels. Consistent across all sittings.
🟢 Biology MCQ technique
- No penalty — attempt every question
- Many questions include diagrams — read labels carefully before the text
- For genetics crosses: draw the Punnett square even in MCQ — it’s faster than mental calculation
- HL: cladogram questions — identify the most recent common ancestor from the diagram
- Eliminate clearly wrong answers first — usually 2 can be ruled out immediately
- Key command words in MCQ: “which”, “most likely”, “explains” — watch the qualifier
Paper 1B — Data-Based Questions
🟡 What Paper 1B tests in Biology: This paper replaced old Paper 3 Section A. It presents real biological data — graphs, tables, electron micrographs, experimental results — and asks you to read, calculate, interpret and evaluate. The biology content can come from any theme, but the skills are always the same: reading graphs, identifying anomalies, calculating percentage change, evaluating experimental design, and suggesting improvements.
🟡 Skills always tested in Paper 1B
- Graph reading — extract values, describe trends, identify anomalies
- Statistical analysis — mean, standard deviation, error bars, t-test interpretation
- Percentage change calculations — very common, easy marks
- Evaluating experimental design — identify variables, suggest controls
- Interpreting micrographs — identify organelles, measure scale
- Suggesting improvements — larger sample size, repeat trials, blind study
🧬 Experimental contexts from Specimen + M25
- Enzyme activity experiment — rate vs temperature/pH graph, Vmax
- Osmosis investigation — potato/onion cells in different concentrations
- Ecology fieldwork data — quadrat sampling, species richness, Simpson’s index
- Population genetics data — allele frequency, Hardy-Weinberg context
- Photosynthesis experiment — light intensity vs rate, absorption spectra
- Practice old Paper 3 Section A questions (2019–2024) — identical skill set
⚠ Key revision tip for Paper 1B: Every mark in Paper 1B is a skill mark. You do not need to memorise content to do well here — you need to practise reading biological data carefully. Practise writing answers in this structure: State the value → Describe the trend → Suggest a biological explanation → Evaluate the method. Command words are everything: “identify” needs 1 mark, “explain” needs 2–3 marks.
Paper 2 — Extended Response (Highest mark value)
🔴 Paper 2 is where Biology exams are won. At 44% for both levels, this is the most important paper. Section A has a mandatory data-based question (must answer all). Section B has short and extended response questions. Extended response questions (6–15 marks each) require knowledge across themes — e.g. “Explain how DNA structure relates to protein synthesis” links Theme D.1 and D.2.
Paper 2 extended response priorities — May 2026
| IB BIOLOGY — PAPER 2 EXTENDED RESPONSE TOPIC FREQUENCY | May 2025 + Mapped 2019–2024 | ||||||||
| Extended questions demand multi-theme synthesis | Command words: explain, evaluate, discuss, compare | HL-only rows greyed in SL view | ||||||||
| Theme | Topic Area | M21 | M22 | M23 | M24 | M25★ | Avg Marks | May 2026 |
|---|---|---|---|---|---|---|---|---|
| THEME D — Most extended Paper 2 marks (DNA/Genetics always tested deeply) | ||||||||
| D.1+D.2 | Molecular biology extended — DNA structure, replication, transcription + translation as one linked question | ✔ | ✔ | ✔ | ✔ | ✔★★ | 12–18 | ⭐⭐⭐⭐⭐ CERTAIN |
| D.3 | Genetics problems — dihybrid cross, linkage, sex-linked traits, pedigree analysis with explanation | ✔ | ✔ | ✔ | ✔ | ✔★★ | 10–16 | ⭐⭐⭐⭐⭐ CERTAIN |
| D.4 | Evolution extended — natural selection mechanism, evidence, Hardy-Weinberg, speciation | ✔ | ✔ | — | ✔ | ✔★ | 8–12 | ⭐⭐⭐⭐ |
| THEME B — Proteins, enzymes and cell function | ||||||||
| B.2 | Protein structure + enzyme function extended — lock-and-key vs induced fit, inhibition types, denaturation | ✔ | ✔ | ✔ | ✔ | ✔★ | 10–14 | ⭐⭐⭐⭐⭐ |
| B.3+B.4 | Cell specialisation + physiology — stem cells, differentiation, gas exchange systems, haemoglobin dissociation | ✔ | — | ✔ | ✔ | ✔★ | 8–12 | ⭐⭐⭐⭐ |
| THEME C — Ecosystems, homeostasis, immunity | ||||||||
| C.1+C.2 | Ecology + biogeochemical cycles — energy loss in trophic levels, carbon cycle analysis, human impact | ✔ | ✔ | ✔ | ✔ | ✔★ | 10–16 | ⭐⭐⭐⭐⭐ |
| C.3 | Immunity extended — antibody production, B and T cells, vaccination, clonal selection, HIV mechanism | ✔ | ✔ | ✔ | — | ✔★ | 8–12 | ⭐⭐⭐⭐⭐ |
| C.4 | Homeostasis extended — negative feedback, insulin/glucagon pathway, kidney structure + function | ✔ | ✔ | ✔ | ✔ | ✔★ | 10–14 | ⭐⭐⭐⭐⭐ |
| HL topics | Chemical signalling, nervous system, epigenetics, cladistics — HL extended questions always include these HL | — | — | — | — | ✔★ | 10–16 | ⭐⭐⭐⭐⭐ HL |
🔴 Paper 2 top priorities
- D.1+D.2 Molecular biology — DNA structure → replication → transcription → translation as one long question. Every year, 12–18 marks.
- D.3 Genetics problems — always a genetics cross question. Know dihybrid, sex-linked, codominance thoroughly.
- C.1 Ecosystems — food chain/web analysis with data. Energy loss calculations always required.
- B.2 Enzymes — graph interpretation + mechanism explanation. Consistent across all sittings.
- C.4 Homeostasis — negative feedback, kidney, glucose regulation. Every year without fail.
✍️ Paper 2 extended response technique
- Use the mark allocation to gauge answer length — 1 mark = 1 distinct point
- For “explain” questions: mechanism + reason + outcome (3-part structure)
- For “evaluate”: state advantage, state limitation, reach a conclusion
- Use correct biological terminology — “phospholipid bilayer” not “fat layer”
- Annotate diagrams — label all parts, add arrows to show direction/process
- For HL: link across themes — examiners reward cross-theme connections
About the new IB Biology syllabus
IB Biology was restructured for first assessment in May 2025. The old 11-topic syllabus has been replaced by 4 conceptual themes (Unity & Diversity, Form & Function, Interaction & Interdependence, Continuity & Change) with 40+ subtopics. Paper 3 is gone. Options (Neurobiology, Biotechnology, Ecology, Human Physiology) are removed, with some content integrated into HL core.
HL vs SL key differences
- Paper 1: SL = 30 MCQ / HL = 40 MCQ
- Paper 2: SL = 50 marks / HL = 80 marks
- HL additions: Cladistics · Chemical signalling · Nervous system & muscle · Epigenetics · Advanced genetics
- Hours: 150 SL vs 240 HL
Want expert IB Biology tutoring?
Sev7n tutors specialise in the new 2025 Biology syllabus. We know every theme, every HL extension.
Book a FREE Demo Class →