What to Expect from the New IB Biology Syllabus 2025

What SL and HL students study

SL and HL students share a common conceptual foundation. HL extends depth rather than introducing a separate body of content.

All students study cell biology (structure, membrane transport, origins of cells), molecular biology (biomolecules, enzymes, metabolism, DNA replication and expression), genetics (inheritance, gene expression, biotechnology), and ecology and evolution (ecosystems, natural selection, biodiversity). These are taught through the four themes throughout the course.

HL students cover additional content within the same thematic framework, including muscle physiology and coordinated movement, chemical and neural cell signalling, regulation of gene expression and the biology of viruses, and cladistics and evolutionary relationships.

The key point for HL students is that this additional content is integrated into the themes rather than treated as bolt-on material. You should be able to connect HL content to the same conceptual threads running through the rest of the course.

Practical work requirements

Practical investigation remains central to the course, with increased emphasis on experimental design, data analysis, and evaluation rather than simply following prescribed procedures.

SL students complete approximately 40 hours of practical work within around 150 total teaching hours. HL students complete approximately 60 hours of practical work within around 240 total teaching hours.

These hours cover hands-on laboratory investigations, data processing tasks, and preparation for the Internal Assessment. The shift in emphasis toward design and evaluation means that understanding why you are doing an experiment, and how to critically assess its results, matters more than it did under the previous syllabus.

Assessment structure

The most notable structural change is the removal of Paper 3, which previously tested option-based content. Assessment now consists of two external papers and an Internal Assessment.

Paper 1 consists of multiple-choice and data-based questions testing conceptual understanding and analytical skills. Questions are aligned to the four core themes.

Paper 2 consists of short-answer and extended-response questions requiring explanation, application, and evaluation. Both papers place heavier emphasis on interpreting biological data than on recall.

Together the external papers account for approximately 80% of the final grade.

The Internal Assessment remains worth 20%. Students design and carry out an individual investigation, typically completed within around 10 hours of class time. The IA rewards originality in research question design, quality of data collection, and depth of analysis and evaluation.

How to study for the new syllabus

The thematic structure of the 2025 syllabus rewards a different kind of revision from what worked under previous versions of the course. Three adjustments matter most.

Organise your notes around themes, not topic lists. When you revise cell biology, ask yourself which theme it belongs to and how it connects to other content you have studied. Exam questions are written to test these connections, and students whose notes mirror that structure tend to answer them more fluently.

Practise data-based questions from the start. Papers 1 and 2 both emphasise data interpretation over recall. The best way to build this skill is to work through exam-style questions regularly, not just before the exam. Pay attention to how mark schemes reward analysis and evaluation, not just correct identification of facts.

Start your IA with the question, not the method. A well-designed research question makes every subsequent stage of the IA easier. Spend time refining it before you commit to a method. The most common IA weakness is a question that is too broad or too descriptive to support genuine experimental investigation.

FAQs

How does assessment differ from the previous syllabus? Paper 3 has been removed. Assessment now focuses on Papers 1 and 2, both of which are fully aligned to the four core themes and emphasise data interpretation and conceptual understanding over option-specific content recall.

Do HL students study more topics than before? HL includes additional depth in areas such as chemical signalling, gene expression regulation, and cladistics. These are integrated into the thematic framework rather than treated as separate extension material.

How much practical work is required? Approximately 40 hours for SL and 60 hours for HL. The emphasis is on experimental design and data evaluation, not just the number of experiments completed.

How is the Internal Assessment changing? The IA format remains similar, but the new syllabus places greater weight on the quality of experimental design and the depth of analysis. A focused, well-justified research question is the foundation of a strong IA.

RevisionDojo provides notes, flashcards, and question banks aligned to the 2025 syllabus, along with IA guidance and exam strategy resources. Visit RevisionDojo.com to explore their IB Biology materials.

Learn why different cells express different genes and how gene regulation enables specialization and diverse cell functions.