Marks-weighted analysis of 269 questions across 855 marks and 15 papers — every sitting of the redesigned IB Biology Higher Level course so far. Theme A–D weightage, the themes × levels-of-organisation grid, the Paper 1A / 1B / 2 split, and the cross-topic synthesis that now dominates the exam.
Percentage of total exam marks allocated to each of the four syllabus themes across all 15 papers, with marks distributed among tags to avoid double-counting.
Enzymes, respiration, photosynthesis, signalling, immunity and populations together take more than a quarter of every mark. Theme C is also the theme most often fused with another in the same question.
C 28.3%, D 26.3%, B 25.6%, A 19.8%. Unlike the old course, there is no dominant unit and no theme small enough to gamble on skipping.
The smallest theme still carries roughly one mark in five — and it holds evolution, speciation, classification and viruses, which recur inside questions belonging to other themes.
The redesigned Biology course is not a list of units; it is a grid. Each of the four themes is developed at four levels of organisation — 1 molecules, 2 cells, 3 organisms, 4 ecosystems — and the exam samples that grid almost uniformly. Figures are the percentage of total marks in each cell.
| Theme | 1 · Molecules | 2 · Cells | 3 · Organisms | 4 · Ecosystems | Theme total |
|---|---|---|---|---|---|
| A · Unity & diversity | 4.0 | 5.9 | 3.3 | 6.6 | 19.8 |
| B · Form & function | 4.6 | 6.7 | 10.1 | 4.2 | 25.6 |
| C · Interaction & interdependence | 10.4 | 5.7 | 4.8 | 7.4 | 28.3 |
| D · Continuity & change | 7.4 | 6.3 | 5.8 | 6.8 | 26.3 |
| Level total | 26.4 | 24.6 | 24.0 | 25.0 | 100 |
The four levels of organisation come out almost perfectly even — 26.4% / 24.6% / 24.0% / 25.0%. Every level is worth roughly a quarter of the paper, so a student who is strong on molecules and weak on ecosystems is not losing a corner of the course; they are losing a full quarter of it.
Enzymes, cell respiration and photosynthesis form the single densest cell in the grid — the molecular end of Theme C alone outweighs several whole themes' worth of a single level.
Gas exchange, transport, and muscle & motility. This cell is unusually heavy on the data paper — it is where physiological experiments and measurement questions are set.
No theme skips a level and no level skips a theme. The smallest cell, organism-level Theme A, still carries 3.3% of marks — comparable to several stand-alone sub-topics.
Every sub-topic ranked by its share of total exam marks. Bars are coloured by theme. HL-only sub-topics are marked "(HL)".
The largest single sub-topic, and heavily weighted to Paper 2 (29.2 of its marks). Sampling, population growth, interactions between species and community data are examined every sitting.
With 40 sub-topics and none above 5.2%, marks are spread thinner than in any other IB science. Betting on ten "big topics" leaves nearly two-thirds of the paper unrevised.
A2.1 Origins of cells, A2.3 Viruses, B3.3 Muscle & motility, C2.1 Chemical signalling and D2.2 Gene expression are HL-only. Beyond these, most HL depth is added inside shared sub-topics rather than as separate units — so HL extension shows up as extra demand in ordinary-looking questions.
An HL-only topic that carries 23.5 marks on Paper 1B alone — far more than any other sub-topic. Sarcomere measurement, contraction data and motility experiments are prime data-analysis material.
The smallest sub-topic by marks — but still examined, usually as a single multiple-choice item or as the framing for a classification question. Low weight does not mean skippable.
Twenty-five of the 40 sub-topics fall in that band. In practice each one is worth about one Paper 1A question plus a Paper 2 sub-part — enough to move a grade boundary.
The new structure splits assessment three ways: Paper 1A (multiple choice), Paper 1B (data-based / experimental) and Paper 2 (extended response). This chart shows the marks each theme carries on each paper — Paper 2 is where almost all the depth (and synthesis) lives.
Around 480 of the 855 marks analysed are on the extended-response paper, and every theme puts between 52% and 60% of its marks there. It is the paper that decides grades — and, as the next section shows, the paper that blends topics the hardest.
Form & function (54 marks) and Interaction & interdependence (47 marks) dominate Paper 1B, where physiology, enzyme kinetics and ecological sampling give the cleanest experimental data. Continuity & change (32 marks) appears least.
Interaction & interdependence (57 marks) and Continuity & change (59 marks) carry the most Paper 1A marks — genetics, division, signalling and metabolism produce the crisp single-answer items multiple choice needs.
All four themes appear on all three papers. There is no "Paper 1A-only" or "Paper 2-only" theme to revise in isolation, and no level of organisation that can be quarantined to a single paper.
The redesigned exams were deliberately built to blend themes inside a single question. You are no longer answering "a genetics question" or "an ecology question" — you are answering one long question that starts in cell biology, moves through physiology, and finishes in ecology or evolution. Because the syllabus is a grid, the questions read across it: the same stem asks you about a molecule, then the cell, then the organism, then the ecosystem. Revising topics in isolation is no longer enough — the marks live in the connections.
How we count this. "Multi-topic" is not a judgement call about how synthesis-like a question feels. It means exactly one thing: the question is tagged against two or more distinct syllabus topics in Photon Academy's own per-question tagging of every paper. "Cross-theme" is the stricter subset — the tagged topics come from two or more different themes (A–D) — so every cross-theme question is also a multi-topic question.
Paper 2 is the clearest signal of the shift: more than nine in ten of its marks are in multi-topic questions, and only three of its 49 questions stay inside a single topic. A single extended-response item can require a signalling pathway, a homeostatic feedback loop and a graph interpretation — all chained together, where an early slip in one theme sinks the marks that follow. Note also the asymmetry: multi-topic questions are only 45.7% of questions but 78.9% of marks, because they are the long, high-tariff items. The examiners reward students who can connect ideas across the grid, not just recall them.
| B + C Form & function + Interaction & interdependenceStructures tied to the processes they serve — gas exchange and transport feeding respiration, immunity or signalling. | ×27 |
| C + D Interaction & interdependence + Continuity & changeMetabolism, signalling and populations linked to homeostasis, gene expression, selection or climate change. | ×24 |
| A + D Unity & diversity + Continuity & changeNucleic acids, classification and evolution meeting replication, mutation, inheritance and natural selection. | ×19 |
| B + D Form & function + Continuity & changeMembranes, organelles and organ systems joined to division, water potential and homeostatic control. | ×15 |
| A + C Unity & diversity + Interaction & interdependenceViruses, cell structure and biodiversity set against defence against disease, metabolism and community ecology. | ×13 |
| A + B Unity & diversity + Form & functionWater, macromolecules and cell structure explaining protein, membrane and organism-level function. | ×7 |
Every one of the 269 questions rated for demand. Most of the paper is squarely mid-difficulty — but roughly one question in five is genuinely hard, and those hard questions are overwhelmingly the multi-topic Paper 2 items above.
Recall, single-step and "state / outline" items — mostly on Paper 1A and the opening parts of longer questions. Reliable marks if fundamentals and terminology are solid.
Around 54% of questions need two or three linked steps — explain a mechanism, read a graph, apply it to a named context. This is where most candidates win or lose their grade, through precision of wording rather than exotic content.
These are the long synthesis questions that chain themes across levels of organisation. Handling them is what separates a 6 from a 7.
Official grade boundaries for the new syllabus.
Because the redesigned course has only just had its first sittings, we are still gathering and verifying the official IB grade-boundary documents for Biology HL. Rather than publish estimated or fabricated numbers, we are leaving this section blank until we have confirmed data. Check back — or ask your IB coordinator for the official boundaries in the meantime.
Full IB-style predicted papers for the new Biology HL course — Paper 1A, 1B and 2 with markschemes — modelled on the synthesis patterns above.
Our tutors are currently writing predicted paper sets for the redesigned Biology HL course, built to mirror the cross-topic Paper 2 style this analysis uncovered. They are not published yet. In the meantime, the fastest way to prepare for a synthesis exam is targeted, tutor-led practice on the exact theme combinations that keep recurring.