IB DP Biology Topics by Exam Board: Full List

As an IB DP Biology student, knowing exactly what topics you need to study—and where to find them—can be overwhelming. 

This article gives you a full breakdown of the IB DP Biology topics you’ll cover, based on the 2025 IB DP Biology syllabus. 

We’ll show you which topics are assessed in each exam paper and where to find the best revision resources to help you succeed at both Standard Level (SL) and Higher Level (HL).

IB Biology Topics

IB DP Biology refers to the International Baccalaureate Diploma Programme. It is divided into four organising themes containing subtopics that are studied at either Standard Level (SL) or High Level (HL). Nature of Science (NOS) is an additional section of the syllabus that assesses experimental work and data analysis. Within each theme, there are four key Levels of Organisation: Molecules, Cells, Organisms and Ecosystems.

Theme A: Unity and Diversity

This theme introduces the fundamental principles that all living organisms share, despite the incredible diversity of life on Earth. You’ll explore the molecular components common to all cells, such as water, carbohydrates, lipids, proteins, and nucleic acids. It also examines how life is classified and the shared features that unite different domains and kingdoms of organisms.

Theme B: Form and Function

This theme explores how the structures of biological molecules, cells, and systems enable them to perform essential functions. You’ll investigate the relationship between form and function across different levels of life, from enzyme activity to organ systems and plant transport.

Theme C: Interaction and Interdependence

This theme examines how biological systems maintain internal stability and interact with each other and their environments. You'll explore feedback mechanisms, communication systems, and ecological relationships that sustain life.

Theme D: Continuity and Change

This theme focuses on how genetic information is inherited, expressed, and modified over time. You’ll explore DNA processes, patterns of inheritance, and how evolution leads to long-term change in populations and ecosystems.

The Nature of Science

The Nature of Science (NOS) is an overarching theme in IB DP Biology that seeks to explore conceptual understandings related to the purpose, features and impact of scientific knowledge. It is embedded across all topics in the IB DP Biology course and encourages you to think like a scientist — not just learning facts, but understanding how biological knowledge is developed, tested, revised, and applied. You’ll explore how theories are built from evidence, how new technologies expand our understanding, and how biology interacts with ethics and society.

There is a range of aspects of NOS that underpin the experimental skills, internal assessment, and many data and context-based questions. These can be summarised as follows:

• Science as a process of constructing knowledge

• The use of models

• Scientific collaboration and communication

• Ethical implications of science

• Creativity and imagination in science

• Reliability, validity, and uncertainty

Assessments

IB DP Biology is assessed through two written exam papers at both Standard Level (SL) and Higher Level (HL), and an Internal Assessment (IA). Each paper has a distinct focus and tests different types of knowledge and skills. Nature of Science (NOS) is assessed in both Paper 1 and Paper 2, though in different ways and to different extents.

What is Covered in IB Biology Paper 1?

Multiple Choice

What it covers:
Paper 1 tests your understanding of the core syllabus content using multiple-choice questions. While Paper 1 mostly tests factual recall and core concepts, some multiple-choice questions are designed to:

• Present data or experimental scenarios

• Require interpretation of trends, anomalies, or the purpose of variables

• Touch on aspects like model use, hypothesis testing, or scientific reasoning

Topics tested:

• SL: All standard level topics across themes A–D

• HL: All standard and higher-level topics, including HL-only material

Key features:

• Standard level contains 30 questions

• Higher level contains 40 questions

• No calculator allowed

• Some questions may be based on short data tables, graphs, or diagrams

• Questions draw from all four themes and levels of organisation

What is Covered in IB Biology Paper 2?

Short answer and extended response

What it covers:
Paper 2 assesses your ability to interpret data, construct scientific explanations, and apply biological knowledge in unfamiliar contexts. This paper also includes many of the Nature of Science (NOS) and experimental design elements previously found in Paper 3.

Topics tested:

• SL: All SL topics from the four themes
  HL: Full syllabus including HL extensions and deeper analysis

Structure:

• Section A: Data-based and structured short-answer questions
  Section B: Extended-response questions — students select from a choice of essay-style prompts

• NOS concepts (e.g. experimental methods, ethics, theory building) are embedded throughout

Internal Assessment (IA)

Alongside the final exams, IB DP Biology includes a compulsory Internal Assessment (IA) — an individual, student-designed investigation that makes up 20% of your final grade at both SL and HL.

The IA is a practical, inquiry-based investigation where you choose a research question, design and carry out an experiment, and analyse your findings. It’s your opportunity to apply the scientific method and show your understanding of biological processes, data handling, and evaluation. NOS is also heavily embedded in the Internal Assessment (IA), where you must demonstrate real scientific reasoning, evaluation, and awareness of the nature and limitations of science.

You must include:

• A clear research question

• Justification of methodology

• Analysis and interpretation of data

• Evaluation of limitations and sources of error

Summary of assessments

Here’s a quick overview of the updated assessment structure:

Revision Resources for IB Biology

The resources below will help you prepare for your IB DP Biology exams (first assessment 2025). They’re specifically tailored to the updated IB Biology syllabus and structured around the four organising themes. Our clear revision notes, exam-style questions with model answers, and flashcards for active recall are designed to help you understand key concepts, practise effectively, and avoid common exam pitfalls.

DP IB Biology: SL Revision Notes

DP IB Biology: SL Exam Questions

DP IB Biology: SL Flashcards

DP IB Biology: HL Revision Notes

DP IB Biology: HL Exam Questions

DP IB Biology: HL Flashcards

DP IB Biology Mock Exams

DP IB Biology Past Papers & Practice Papers

Improve Your Grades with Save My Exams

Studying IB Biology can be challenging, but Save My Exams makes it easier and more effective. Our resources are designed to help you focus on what really matters — with clear, syllabus-specific revision notes, exam-style questions with detailed mark schemes, and engaging flashcards to build long-term memory through active recall.

Whether you're revising for mock exams or preparing for your final assessments, Save My Exams gives you the tools and confidence to succeed. All our materials are carefully aligned with the 2025 IB Biology syllabus and are created by experienced teachers and examiners who know what examiners are really looking for. You’ll avoid common mistakes, strengthen your understanding of tricky topics, and gain the skills to tackle data-based and extended-response questions with confidence.

Explore Our DP IB Biology Resources

References

Studying the Diploma Programme (DP) biology