Overview
The IB Biology syllabus was rebuilt for first examinations in May 2025 (first taught 2023), and the changes are structural, not cosmetic. Content is now organised around four themes tied to big ideas rather than a long list of separate topics, the old options were removed so everyone studies one common body of content, and assessment was streamlined to two exam papers instead of three. The underlying biology is largely familiar — but how it is arranged, and how you are expected to connect it, has changed. Here is what actually moved, and what it means for how you revise.
The headline changes at a glance
If you have old notes, past papers, or a tutor working from the previous course, the fastest way to orient yourself is to see the differences side by side.
| Area | Old syllabus | New (2025) syllabus |
|---|---|---|
| Structure | Numbered topics studied one after another | Four themes built on big ideas, explored across levels of organisation |
| Options | Optional topics chosen from a menu, sat on a separate paper | No options — a single common core for everyone |
| Exam papers | Three papers (the third covered the options) | Two papers — options paper gone |
| Focus | Topic-by-topic coverage | Connections and transferable concepts across biology |
Everything below unpacks these rows. Where exact timings and weightings matter, check the official IB subject guide or your teacher for the current figures — those details get revised between sessions and are not worth memorising from a blog.
The four themes and big ideas
For the IB Diploma Programme, the biggest conceptual shift is the move from a topic list to a theme-based framework. The course is now organised around four themes, each anchored to a "big idea" that recurs throughout biology:
- A — Unity and diversity: what living things share, and how variation arises.
- B — Form and function: how structure relates to what a biological feature does.
- C — Interaction and interdependence: how components influence one another, from molecules to ecosystems.
- D — Continuity and change: how life persists and how it transforms over time.
The clever part is the second axis. Each theme is explored across levels of biological organisation — molecules, cells, organisms, and ecosystems. So "form and function" is not one chapter; it appears again and again, at the scale of a protein, a cell membrane, an organ, and a whole ecosystem. The framework is designed to make you notice that the same underlying idea shows up at every scale.
This replaces the old approach, where you might learn cell respiration in one topic and ecology in another with little pushing you to link them. The 2025 course expects biology as a connected web, not a stack of separate boxes.
Options removed — what it means
For the IB Diploma Programme, under the previous syllabus, students (guided by their school) picked from a set of optional topics and were examined on them separately. The 2025 syllabus removes options entirely. There is now a single common body of content that every candidate studies — no menu, no school-by-school variation in what gets taught.
For you, this cuts both ways. You lose the ability to lean into a favourite specialism, but you gain a clearer, more predictable scope: every marking point comes from content you are guaranteed to have covered. It also means older resources built around a specific option are now off-syllabus, so be careful reusing them.
The streamlined assessment
For the IB Diploma Programme, dropping the options also simplified the exams. The old structure had a third paper dedicated to the option content; that paper is gone. The written assessment is now two papers:
- Paper 1 — an objective paper combining a multiple-choice section (spanning the syllabus) with a data-based section.
- Paper 2 — short-answer and extended-response questions.
Fewer papers means broad, gap-free recall matters even more: with the options gone there is nowhere to hide a weak area. For the exact durations, mark totals, and weightings of each paper — and how they split between SL and HL — check the current specification or ask your teacher, since those figures are the kind of detail IB adjusts and this post won't invent numbers.
What stayed the same
For the IB Diploma Programme, it is easy to over-panic about a "new syllabus," but a lot carried over:
- The internal assessment is still a scientific investigation — an individual, hands-on inquiry marked against set criteria, contributing to your final grade independently of the exams.
- SL and HL still share a common core, with additional higher level (AHL) content layered on for HL students. The two levels are not separate courses; HL is the core plus extension.
- The core biology is largely familiar — cells, biochemistry, genetics, physiology, ecology, and evolution are all still there. They have been reorganised under the themes, not replaced.
- Skills, tools, and the nature of science are integrated throughout rather than bolted on, so practical technique and scientific thinking are assessed alongside content.
If you are weighing the two levels, our IB Biology SL vs HL guide breaks down the extra AHL load in detail.
What this means for your revision
For the IB Diploma Programme, the theme-based structure changes *how* you should study, not just *what*. Three practical implications:
- Revise by connection, not by isolated topic. Instead of memorising respiration as a standalone unit, ask how it illustrates "form and function" at the molecular level. Questions reward students who can link ideas across themes.
- Study each idea across levels of organisation. When you learn a concept, trace it from molecules to ecosystems — that is the exact axis the syllabus is built on, so it is the axis examiners think in.
- Cover everything. With no options and only two papers, there is no optional territory to specialise in. Broad, even coverage protects you from the multiple-choice section that can quietly drain marks.
How to study the new syllabus
For the IB Diploma Programme, a simple loop works well for a themed course:
- Map the theme first. Before drilling detail, sketch how a theme's big idea plays out at each level of organisation. This gives every fact a place to hang.
- Learn the content, then self-test. Use active recall — blank-page summaries and flashcards — rather than rereading. Rereading feels productive but rarely moves your grade.
- Practise to the mark tariff. On Paper 2, each mark is a separate valid point; count them out before you write. Our how to get a 7 in IB Biology guide covers the point-per-mark technique in full, and the SL past papers guide gives you a full-paper routine.
- Mark honestly and log why you lost each mark — missing point, wrong command term, or missing units.
How MarkScheme helps
Our IB Biology courses are built on the 2025 syllabus, so you are learning the current theme-based content, not an outdated topic list. Work through the free [IB Biology SL course](/ib/courses/biology-sl) or [HL course](/ib/courses/biology-hl) to cover each theme across the levels of organisation, then [get an answer marked](/mark) for point-by-point feedback aligned with IB assessment objectives — so you can see exactly which marking points you are missing before exam day. Browse the [IB guides hub](/guides/ib) for subject-wide strategy.
Frequently asked questions
This section covers Frequently asked questions — what IB examiners reward most often in past papers and coursework.
When are the first exams for the new IB Biology syllabus?
The first examinations for the current IB Biology syllabus were in May 2025, with first teaching in 2023. If you are sitting exams in 2025 or later, you are on the new theme-based course. Confirm your exact session with your teacher.
Are there still options in IB Biology?
No. The options were removed in the 2025 syllabus. Everyone now studies a single common body of content, with AHL material added for HL students. There is no separate options paper.
How many exam papers are there now?
Two. Paper 1 combines multiple-choice and data-based questions; Paper 2 is short-answer and extended-response. The old third paper that covered the options no longer exists. For exact timings and weightings, check the official IB subject guide or your teacher.
What are the four themes in IB Biology?
A — Unity and diversity, B — Form and function, C — Interaction and interdependence, and D — Continuity and change. Each is explored across levels of biological organisation, from molecules and cells to organisms and ecosystems.
Did the internal assessment change?
The internal assessment remains an individual scientific investigation marked against set criteria, contributing to your final grade alongside the exams. Its role as hands-on, student-controlled coursework carried over to the new syllabus.