What is IB Biology?

IB Biology is part of the Diploma Programme. It covers living systems, from molecular biology to ecosystems, while also developing scientific literacy and independent thinking. Students studying IB biology will gain:

• biological knowledge

• an understanding of the nature of science, i.e. how scientific knowledge is developed and applied

• knowledge of global and real-world issues

• research, collaboration, and data analysis skills

Whether you're considering medicine, environmental science, or simply want to understand the biological world around you, IB Biology is a highly respected choice by universities around the world.

HL vs SL: what's the difference?

You can take IB Biology at Higher Level (HL) or Standard Level (SL). Both levels offer a rigorous course of study, but there are important differences between the two. 

The choice between SL and HL often depends on your future academic plans; HL Biology demands significantly more time and effort, but it is necessary if you're considering science at university, especially medicine or biological sciences.

What will you study in IB Biology?

IB Biology content is grouped into four themes, each explored in multiple contexts at both SL and HL.

Core Topics (HL and SL)

IB Biology core topics provide the foundation for understanding life. These core topics interconnect throughout the course, helping you develop a coherent understanding of biological systems.

• Theme A: Unity and Diversity

  • Water, nucleic acids, and basic cell structures

  • Classification systems and species concepts

  • Evolution and biodiversity

• Theme B: Form and Function

  • Carbohydrates, lipids, and proteins

  • Cell membranes and organelles

  • Gas exchange, transport, and adaptations to the environment

• Theme C: Interaction and Interdependence

  • Enzymes, respiration, and photosynthesis

  • Nervous/hormonal coordination and immunity

  • Ecosystems and nutrient cycles

• Theme D: Continuity and Change

  • DNA replication and protein synthesis

  • Cell division, inheritance, and reproduction

  • Homeostasis and natural selection

Additional HL Topics (HL only)

HL students explore each theme in greater depth, building on the core content and engaging with more advanced biological concepts. These topics provide strong preparation for university-level biology and reflect current areas of scientific research.

• Theme A: Unity and Diversity

  • The origins of cells

  • Structure of RNA and DNA; evidence for DNA as genetic material

  • Viral diversity and the features of viruses

  • Challenges in defining species; use of dichotomous keys; significance of chromosome numbers

  • Clades, molecular clocks, and evolutionary trees

  • Mechanisms of speciation and abrupt speciation

  • Adaptive radiation and its role in evolution

• Theme B: Form and Function

  • Four levels of protein structure

  • Membrane fluidity and advanced transport mechanisms

  • Structural adaptations in specialised cells

  • Foetal vs adult haemoglobin and oxygen transport adaptations

  • Details of transport systems in animals and plants

  • The sliding filament model of muscle contraction

• Theme C: Interaction and Interdependence

  • Enzyme regulation of metabolic pathways

  • Detailed steps of aerobic respiration and photosynthesis

  • Intracellular and intercellular signalling mechanisms

  • Neural signalling processes, including synaptic transmission

  • Chemical signalling in plants

• Theme D: Continuity and Change

  • Mechanisms of DNA replication and protein synthesis

  • Gene editing technologies

  • The cell cycle and its regulation

  • Gene expression and epigenetics

  • Solute and pressure potential in calculating water potential

  • Human reproduction, including gametes, fertilisation, and pregnancy

  • Chi-squared test and patterns of inheritance

  • Hardy–Weinberg equilibrium 

  • Kidney function in osmoregulation and excretion

  • Types of natural selection and Hardy-Weinberg equilibrium

  • Ecological succession and phenology

Have a look at our IB exam topic article for more details on the topics covered in IB Biology:

• IB DP Biology Topics by Exam Board: Full List

How is IB Biology Assessed?

IB Biology assessment combines external examinations with internal coursework. 

• Paper 1 consists of multiple-choice questions and data-based questions that test knowledge and understanding across all topics. 

  • SL students sit one exam with a total exam time of 1 hour 30 minutes and a total of 55 marks. The paper has two subparts:

    • Paper 1A - Multiple choice questions

    • Paper 1B - Data-based questions

  • HL students sit one exam with a total exam time of 2 hours and a total of 75 marks.The paper has two subparts:

    • Paper 1A - Multiple choice questions

    • Paper 1B - Data-based questions

• Paper 2 includes data-based questions and extended response questions. 

  • SL students sit one exam with a total exam time of 1 hour 30 minutes and a total of 50 marks. The exam has two sections:

    • Section A - Data-based and short-answer questions

    • Section B - Extended response questions

  • HL students sit one exam with a total exam time of 2 hours 30 minutes and a total of 80 marks. The exam has two sections:

    • Section A - Data-based and short-answer questions

    • Section B - Extended response questions

  • Questions require analysis, evaluation, and application of biological knowledge

• Internal Assessment (IA) involves designing, conducting, and evaluating a biological investigation

  • SL and HL students both have 10 hours allocated to completion of the internal assessment, which is internally assessed and externally moderated.

The Extended Essay is optional but popular among biology students. This 4,000-word research essay allows deep exploration of a specific biological topic and can contribute to the overall diploma score. The EE can go beyond the syllabus, provided the research is grounded in biology and follows IB criteria.

What skills will you develop in IB Biology?

IB Biology develops transferable skills that benefit academic study and future careers across many fields.

• Scientific thinking helps you to approach problems systematically, form hypotheses, and evaluate evidence objectively.

• Practical skills include experimental design, data collection, and laboratory safety procedures.

• Data analysis skills develop through working with complex datasets, creating graphs, and identifying patterns in biological data.

• Scientific writing improves through report writing, IA completion, and exam responses.

• Critical evaluation abilities develop as you assess the reliability of scientific studies, identify limitations in experimental design, and compare different research approaches.

• Independent research experience through the IA develops self-direction, time management, and project planning abilities.

• Global awareness grows through studying biological issues from international perspectives and recognising the global nature of scientific collaboration.

Is IB Biology right for you?

Consider these questions to determine whether IB Biology aligns with your interests and goals:

• Are you curious about how living things work?

• Can you manage long-term projects and deadlines?

• Do you enjoy independent research and lab work?

• Do you want to build confidence with data and basic maths?

• Do you plan to study life sciences at university?

If you answered yes to most questions, IB Biology could provide a rewarding and valuable educational experience that opens doors to exciting career opportunities.

How to succeed in IB Biology

IB Biology is hard work — there's a lot to learn and many skills to develop. But with the right habits and mindset, you can stay on top of the work and gain high marks.

Here’s how to set yourself up for success:

Build smart study habits early

• Use active recall: don’t just reread your notes. Quiz yourself, use flashcards, and explain things out loud to others.

• Try spaced repetition: spread out your revision and be sure to revisit each topic multiple times

• Review regularly: set aside time each week to go back over older topics so they stay fresh in your memory.

• Join or start a study group: teaching others is one of the best ways to learn.

Know your exams — and practise them

IB Biology exams are specific in how they ask questions — and what they expect in your answers. Learn the exam style, and how to answer the different types of questions.

• Practise past paper questions and then check your answers against the mark schemes.

• Learn how to apply command terms: words like “describe”, “explain”, “analyse”, and “evaluate” all mean different things — and examiners expect you to know the difference.

• Understand how marks are awarded: read mark schemes carefully, and learn what gets a mark — and what doesn’t.

• Watch your timing: don’t let one question eat all your time. Practise staying within the limits so you’re ready on the day. 

Having marked many practice papers in the past, I’ve found that students who approach questions with the examiner’s perspective — carefully considering the mark scheme as well as the question — consistently perform better.

Approach your IA like a scientist

The Internal Assessment (IA) is worth 20% of your final grade — and it’s entirely within your control. Treat it like a mini research project.

• Pick a topic that interests you: from supporting students with similar coursework in other biology programmes, I’ve seen how choosing a topic you genuinely care about makes a huge difference; you’ll stay motivated through the research and produce a stronger final investigation.

• Keep it manageable: a focused, well-designed experiment is better than a complicated one with too many variables.

• Start early: planning, data collection and writing all take time, so avoid any last-minute panic.

• Do a pilot test: try out your method before committing to the full investigation; this will save you time later on.

• Use the criteria: know what you're being assessed on — and make sure your write-up hits every strand (e.g. analysis, evaluation, and personal engagement).

Use the right resources

The IB is different to other post-16 biology courses, so stick to reliable resources that are designed for the IB.

• Use the official IB Biology guide and specimen papers so that you know exactly what’s expected.

• Get a good textbook that is aligned to the current version of the syllabus and exam.

• Try Save My Exams: you’ll find IB-specific revision materials, including notes, topic questions, flashcards and mock exams.

Frequently asked questions

What is the difference between IB Biology and A Level Biology?

Having taught A Level biology extensively, I’ve seen how IB differs in its approach.  While there is significant overlap in the content covered by IB and A Level Biology, the IB takes a more context-driven approach, and covers some concepts that do not appear at A Level. IB Biology also has a greater emphasis on international perspectives, practical investigation skills, and interdisciplinary connections.

Do universities prefer HL Biology over SL for science courses?

Most competitive science programmes strongly prefer or require HL Biology. Medical schools particularly value the additional depth, research experience, and analytical skills that HL provides.

Can I take HL Biology without HL Chemistry?

While it is possible, taking HL Biology without HL Chemistry may limit university options for certain science programmes. Many biochemistry, molecular biology, and medical programmes require both subjects at HL.

Consider your future academic plans carefully when choosing HL subjects; if you're uncertain, consult university admission requirements for programmes that interest you before making final subject choices.

How long should I spend on IB Biology revision per week?

Most successful students spend 4-6 hours per week on HL Biology and 3-4 hours per week on SL Biology, including homework, regular recaps, and IA work.

During exam preparation periods, increase this to 8-10 hours per week for HL and 6-8 hours per week for SL. Quality of study time matters more than quantity - focused, active learning is more effective than passive reading.

Is IB Biology good preparation for medical school?

IB Biology provides excellent preparation for medical school through its emphasis on scientific reasoning, research skills, and analytical thinking. The IA experience is particularly valuable for understanding medical research methodology.

Final thoughts

IB Biology is demanding but incredibly rewarding for curious, motivated students who want to understand the biological world around them. The course will challenge you to think critically, conduct independent research, and engage with current scientific issues.

Get support when you need it, practise regularly, and make use of high-quality resources. It can also help to engage with current biological research, explore local ecosystems, and connect your learning to real-world applications. This approach not only improves exam performance but also develops the scientific literacy and curiosity that will serve you throughout life. 

Explore Our IB Biology Resources