IB Biology: Everything You Need to Know

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IB Biology Guide
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IB Biology is one of the toughest courses in the IB Diploma Programme. With its vast content spanning genetics, biochemistry, human anatomy, and more, it can seem quite overwhelming. However, with smart preparation and consistent practice, you can confidently achieve your desired grade. But first of all, you need to understand what to expect from your academic journey. This is what our comprehensive IB Biology guide is all about.

Read on to find out what you’re going to learn, in which way, as well as how you can improve your performance.

Who Should Study IB Biology and Why?

IB Biology is a challenging but incredibly rewarding course. It gives knowledge about life itself and its various forms from the microscopic cells to the ecosystems we inhabit. So, if you have always been interested in learning about the world around you and yourself as part of it, then IB Biology could be the right choice.

But the course isn’t just for curious minds. It can give you many benefits, namely:

  1. A strong foundation in the sciences. IB Biology is ideal for students who wish to pursue careers in medicine, research, or environmental science. With a focus on topics ranging from human anatomy to ecology, it provides a solid understanding of the natural world.
  2. Valuable skills. IB Biology isn’t about memorising facts. Instead, the learning process is built around dissecting complex information, investigating, and interpreting data like a true scientist. As a result, you have a chance to improve your critical thinking, problem-solving, and analytical skills, which you will need in your future education and career.
  3. Standing out from the crowd. In today’s competitive world, taking an IB Biology course can give you an edge. Universities recognize the rigour and depth of the IB programme, and completing IB Biology can show them your passion for science and commitment to academic excellence.
  4. Access to great careers. The knowledge and skills you gain from IB Biology can open doors to a wide range of exciting careers. For example, you can become a doctor, researcher, environmentalist, biomedical engineer, forensic scientist, or microbiologist.
  5. Potentially higher income. Studies in the USA show that students who learn Biology earn approximately $ 10,000 more than the median household item. So, it’s worth considering Biology if you want your future job to be not only fascinating but lucrative.

Is IB Biology Hard?

According to the IB students themselves, Biology is a rather demanding course, which is second in complexity only to Chemistry and Physics. Although many students found understanding biological concepts relatively straightforward, the sheer volume of material was overwhelming.

One mistake students can make is thinking that Biology is the easiest Science choice. In fact, this is not true and can lead to students struggling on the course when they discover it is much harder than they first imagined.

Now let’s take a look at some statistics. According to the IB Provisional Statistics Bulletin 2023, the average Biology grade at HL is 4.6, which is exactly the same as the mean score for the entire Diploma Programme. Moreover, 11% of students got to earn the highest grade of 7. At SL, the average was much lower – 3.7, and only 3% of students received the maximum grade. If we compare these results with other Science disciplines, only Computer Sciences had a lower average grade.

So, we can conclude that IB Biology is demanding and it’s not the easiest to score high.


The course covers a broad spectrum of topics, from the machinery of cells to complex ecosystems. You will definitely need to read and memorise a lot. However, it shouldn’t be a problem if you develop effective study habits and time management skills.

On the other hand, the challenge is what makes IB Biology so rewarding. It pushes you to think critically, analyse information from multiple angles, and apply your understanding to real-world scenarios. The course might require some intellectual heavy lifting.

IB Biology Syllabus

As we have already pointed out, IB Biology students learn a lot of content. To ease the course load, the new syllabus (first examination 2025) reduces the programme by around 5%. Along with that, it ditches the linear order of topics. With the freedom to choose what and when to cover, teachers can help students find connections between different topics. This way, they can see the big picture of biology – how everything fits together.

Despite this overhaul, the total teaching time remains the same – 110 and 180 hours for SL and HL, respectively.

Apart from that, the syllabus provides significant opportunities for Scientific investigation.

  • Practical work (20 hours at SL and 40 at HL) is your chance to deepen your understanding of Biology. It may include a wide range of activities that bring biology to life, from lab work to technology-based modeling.
  • Collaborative Sciences Project is an interdisciplinary 10-hour project designed to tackle real-world problems using knowledge from multiple science subjects. You’ll team up with your peers who study Physics, Chemistry, or Computer Science to uncover global interconnectedness. Not only does this project promote teamwork, but also allows for honing ATL skills.
  • Scientific Investigation is part of Internal Assessment. In a nutshell, it is a self-directed investigation into a research question that you choose on your own. You can work independently or in a small group with your classmates. Besides choosing a unique research question, you need to carry out experimentation, analyze results, and write a 3000-word report documenting the investigation. The syllabus allocated 10 hours to complete the Scientific Investigation. We have some tips on how to write your IB Biology Internal Assessment – make sure to use it to maximize your marks.

IB Biology Topics

The entire IB Biology syllabus is divided into four units:

  1. Unity and diversity (19 teaching hours for SL and 33 the HL):
    • Water;
    • Nucleic acids;
    • Origins of cells (HL only);
    • Cell structure;
    • Viruses (HL only);
    • Diversity of organisms;
    • Classification and cladistics (HL only);
    • Evolution and speciation;
    • Conservation of biodiversity;
  2. Form and function (26 and 39 teaching hours for SL and HL respectively):
    • Carbohydrates and lipids;
    • Proteins;
    • Membranes and membrane transport;
    • Organelles and compartmentalization;
    • Cell specialization;
    • Gas exchange;
    • Transport;
    • Muscle and motility (HL only);
    • Adaptation to environment;
    • Ecological niches;
  3. Interaction and interdependence (31 teaching hours for SL and 48 for HL):
    • Enzymes and metabolism;
    • Cell respiration;
    • Photosynthesis;
    • Chemical signaling (HL only);
    • Neural signaling;
    • Integration of body systems;
    • Defense against disease;
    • Populations and communities;
    • Transfer of energy and matter;
  4. Continuity and change (at SL, there are 34 teaching hours, and 60 at HL):
    • DNA replication;
    • Protein synthesis;
    • Mutations and gene editing;
    • Cell and nuclear division;
    • Gene expression (HL only);
    • Water potential;
    • Reproduction;
    • Inheritance;
    • Homeostasis;
    • Natural selection;
    • Sustainability and change;
    • Climate change.

IB Biology HL or SL: What Should I Choose?

For those students who aren’t fans of the Sciences in general Biology can seem an easier option than either Physics or Chemistry.  However, this doesn’t mean it is easy, particularly at Higher Level. For this reason we would always suggest you think twice when thinking of choosing this option at HL if Sciences are not your strength.

Ultimately, the perceived difficulty of IB Biology, Chemistry, or Physics varies from student to student. It’s essential to consider your own interests, strengths, and career goals when selecting the science course that is right for you.

Both SL and HL will introduce you to the most important concepts, but the route to gaining Biology knowledge will be a little different. More specifically, HL is a longer ride with 240 hours of course time while SL will walk you through the basics within 150 hours.

Having said that, the course load isn’t what sets the levels apart. Here is how they differ and why you might want to choose one or the other.

IB Biology High Level:
  • It is clearly more challenging. It covers more complex topics and extra details on such concepts as viruses, gene expression, and muscle function. It’s perfect if you want to know more about Biology.
  • It is a good choice for a Biology focused academic career path. If you’re dreaming of a career in a biology-related field or medicine, HL can provide a stronger foundation and prepare you for university-level work, and for some courses it is an essential requirement
IB Biology SL:
  • SL focuses on core biological concepts to provide a solid understanding without the extra depth. It’s a great choice if you want a strong biology background without feeling overwhelmed.
  • Have different career plans? Do you find Biology interesting but it is not your main passion? Then SL allows you to explore the subject while freeing up time for other strong areas.

Before deciding between HL and SL, check if your dream university/course combination has specific requirements for Biology. For example, to study Biology at Oxford University, you need a 7 in Higher Level Biology, Science, or Math. So, research HEI requirements and choose the level that best aligns with your goals.

What does the IB Biology Assessment Involve?

Starting from the 2025 examinations, Biology students will take two exams instead of three. The IBO has removed Paper 3 to reduce stress and provide a more balanced experience for students. Yet, the remaining Papers still maintain academic rigor – the total exam time and the number of marks are the same as before. Overall, with a focus on practical skills, teamwork, and higher-order thinking, the assessment format gives a great foundation for further studies and careers.

Paper 1

Paper 1 constitutes 36% of the final grade. It consists of two sections:

  • Section A: Multiple-choice questions test the breadth of biological knowledge.
  • Section B: Data-based questions assess practical skills and understanding of experimental work.

The duration of Paper 1 is 1.5 hours at SL, with a maximum of 55 marks, and 2 hours at HL with up to 75 marks.

Paper 2

Paper 2 involves deeper analysis and explanations in the form of short and extended answers. SL students must provide one extended response question from two choices to earn a maximum of 50 marks. Their HL peers answer two extended-response questions from three choices, with a chance to get 75 marks. In both cases, Paper 2 contributes 44% to the final score.

Internal Assessment, alternatively known as Scientific Investigation, weighs 20% of the overall score. It allows students to work in groups of up to 3 to develop teamwork and peer learning skills. Still, each member of the team has to come up with their own research question, collect independent data, and write a separate report of up to 3000 words.

The Scientific Investigation rewards 24 marks distributed across 4 criteria: Research design, data analysis, conclusion, and evaluation. Each criterion brings 6 marks, which means that higher-order skills (critical thinking, analyses, reflection, etc.) are now more important than ever.

How to Study IB Biology?

Studying IB biology is not a walk in the park because of its vast, information-packed syllabus. However, with the right strategies and mindset, you can navigate the subject with ease. Below are some tried-and-true tips to help you study IB biology more effectively.

Study the Curriculum

Before you dive into the nitty-gritty of IB biology, it’s important to understand what the curriculum entails. First, you need to take a look at key concepts, topics, and learning objectives. The syllabus, however, is the most important part since it provides the unit-by-unit breakdowns. They will come in handy to create a study plan as well as when you prepare for your exams.

Practice Active Learning

Reading textbooks and lecture notes is not enough to truly memorise information. It is best to combine passive reading with active learning techniques that engage your brain.

For example, you can create flashcards or mind maps for key concepts and processes. Another great way to commit information to memory is by teaching the concepts to someone else such as a friend or family member. Explaining a topic in your own words not only reinforces your understanding but also helps identify any gaps in your knowledge.

Asking questions is also important to stimulate deeper thinking. It will force you to analyse the information and identify areas where you need clarification. Eventually, it can allow you to develop a better understanding of the material.

IB coordinators on our teaching team say this is what they want students to do all the way through the course.  After all, you don’t want to find yourself in your IB2 year and that you haven’t managed to fully grasp the work from year one!

Start Practicing With a Tutor

Even with the best effort, some concepts in IB biology can be too hard to grasp on your own. That’s why a tutor’s assistance can be invaluable. At TutorsPlus, we have experienced IB biology tutors who can clarify uncertainties, contribute to resolving your practice problems, and provide personalized guidance.

Let’s say you’re struggling to understand DNA replication. Our tutor can break it down into smaller steps, provide visual aids, and give you targeted practice exercises to build your confidence in working with the material.

Use a Variety of Resources

Your textbook isn’t the only resource you can use. Other learning materials, such as video tutorials, podcasts, and educational websites, provide different learning formats. Diversifying your resources not only keeps your studying interesting but also exposes you to different perspectives.

Stay Organised and Patient

Because IB Biology covers a lot of material, it is important to stay organised and motivated throughout your journey. A comprehensive study schedule allocating time for each topic can help you stay on track. This schedule should also include regular review sessions and breaks to avoid burnout.

Remember, mastering complex biological concepts takes time and repetition. Don’t get discouraged if you don’t understand something immediately. Instead, take a step back, review the material from a different perspective, and seek help from your tutor or teacher if you feel you need it.

IB Biology Conclusion

And that was our comprehensive IB Biology guide! The TutorsPlus team hopes it can answer all your questions whether you’re just considering including Biology in your diploma programme or already studying.

All in all, IB Biology is a great choice if you want to understand how the human body and other living organisms, function. Yet, you need to realise that Biology is a challenging subject, with a lot of complex concepts and a variety of practicals. At some point, you might find yourself stranded. If this happens, don’t be shy to call for help.

TutorPlus tutors are passionate about Biology and have helped many students successfully navigate the ups and downs of IB Biology. Here’s how we can support your learning journey:

  • Customized revision plans targeting areas you struggle with;
  • In-depth study of syllabus topics to strengthen conceptual knowledge;
  • IA brainstorming and reviews to help craft an outstanding investigation;
  • Mock exams that simulate the real IB test experience;
  • And much more.

With an approach combining effective teaching, comprehensive revision resources, and personalised mentoring, we can help you do your best in Biology. Reach out to us today at +41 022 731 8148 or info@tutorsplus.com to start your journey towards IB Biology success!


Which to Choose: IB Biology or A-level Biology?

Both IB and A-Level Biology are widely recognised courses for high school students interested in pursuing a biology-related path. While they share many similarities in their curriculum, their key differences may greatly impact your learning experience.

Breadth vs. Depth

IB Biology takes a broader approach envisioning learning a greater number of topics. This can translate to a wider foundation of knowledge but requires a stronger time management and study strategy.

A-Level Biology, on the other hand, focuses on fewer topics, which results in a more in-depth exploration. Such an approach is beneficial for those who prefer to delve deeply into specific areas of biology.

Developing Critical Skills

IB Biology places a great emphasis on developing scientific inquiry and critical thinking. Throughout the course, students learn to apply them in various contexts such as research projects and practicals. This can make IB Biology more challenging. However, all this work pays off as students gain a deeper understanding and critical approach to scientific concepts.

In contrast, A-Level Biology generally focuses more on traditional exam preparation and knowledge retention.

Choosing Your Path

The ultimate choice of qualification depends on your learning style and goals. If you’d like to learn a broader scope of topics and apply knowledge in real-life situations, then IB Biology could be a good fit. Conversely, if you prefer to learn fewer topics but more extensively, A-Level Biology might be a better choice.

Is There a List of Recommended Textbooks or Resources for IB Biology?


Online Resources

  • Bioknowledgy is your personal training ground for exam success. Their “Quick Quiz” section lets you test your knowledge of specific lessons after watching a presentation.
  • BioNinja offers everything from comprehensive study guides and detailed summaries to interactive simulations that bring complex topics to life.
  • Quizlet provides various Biology resources including quizzes, flashcards, and textbook solutions.
  • IB World has learning materials for every IB Biology topic. Although it is structured around the older syllabus, it is still useful.

Educational YouTube Channels

  • Alex Lee’s channel provides in-depth coverage of most IB Biology topics. Albeit old, the videos are conveniently labelled using specific IB topics.
  • Amoeba Sisters videos cover various Biology topics, including those you will encounter at SL and HL. While not categorized by IB topics, they offer an excellent platform for focused learning.
  • Crash Course Biology Playlist is for you if you enjoy longer, comprehensive explanations with a dash of humour.
  • Biology Lab Techniques provides videos on the practical aspect of mastering Biology.

Which IB Biology Topics are Considered the Most Difficult?

A survey conducted at one of the high schools revealed that students find the following topics the hardest:

  • Bacteria and Viruses. This might be due to the complexity of their structure, diverse life cycles, and intricate interactions with other organisms.
  • Endocrine System. The complex interplay of hormones and their effects on various bodily functions can be difficult to grasp.
  • Cell Structure. While seemingly fundamental, the number of organelles within a cell, their specific functions, and their interactions can be too much to handle for many students.
  • Genetics. This topic can be daunting due to its extensive terminology, complex concepts like inheritance patterns, as well as the abstract nature of genes and chromosomes. Besides, the lack of readily observable real-world examples can further hinder visualisation and understanding.
  • Nervous System. The structure and organisation of the nervous system, along with the complex neural pathways and their various functions, can be challenging to comprehend.

Besides that, many students struggle with the Nuclear Acids topic due to its abstract nature, as well as Cell respiration and Photosynthesis because of an overwhelming amount of content and hard-to-understand concepts.

What are the Most Common Mistakes When Studying IB Biology?

You can study IB Biology much more effectively if you steer clear of these common mistakes.

First, don’t solely rely on textbooks. There are many resources around including videos, simulations, online forums, etc. that can provide different angles on the things you learn at school.

Second, don’t skip over practical work. Hands-on experiments are an important part of the Biology syllabus since they teach how you can apply theoretical knowledge in real life.

Another blunder is cramming everything at the last minute. IB Biology requires consistent, smart studying from the very beginning. There is a lot of material to learn during your two-year journey but if you break the syllabus into manageable sections, you will get to understand even the most complex concepts, one step at a time.

It is also a bad idea to go solo. Instead, you can find a study buddy or seek help from tutors when struggling. An extra set of eyes can clarify confusing topics.

By Sara Lloyd

Sara has been an education consultant for TutorsPlus for 15 years, and is an expert on international IB education.  She is also a parent of two lively children.

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