Hardest IB Biology Questions & How to Answer Them
Written by: Naomi Holyoak
Reviewed by: Cara Head
Published
Contents
You're aiming for a 6 or a 7 in IB Biology. You've revised the content and you've memorised the definitions, but when you open past papers, some questions still give you a panicky feeling.
This can happen because the hardest IB Biology questions don't just test what you know. They test whether you can apply that knowledge to unfamiliar scenarios, draw ideas from multiple topics, and construct answers that are logical and detailed. These are the questions that separate genuine biological understanding from memorisation alone.
Here's the good news: tricky questions follow predictable patterns. Once you understand what makes them difficult and how examiners award marks, you can tackle these challenges with confidence.
As experienced IB Biology educators who've helped thousands of students achieve top grades, we know exactly which questions trip students up and why. Let's get started.
Key takeaways
Hard IB Biology questions don’t just test recall; they combine topics, use unfamiliar contexts and deal with demanding data.
Examiners use precise mark schemes, so how you handle command terms, structure your answers and choose terminology has a big impact on your marks.
Simple in-exam strategies, such as decoding the question, stripping scenarios back to core biology, building stepwise explanations and managing time, make difficult questions more manageable.
Active practice with past papers and mark schemes will help you to recognise patterns, develop level 7 habits and turn tough questions into a strength.
What makes an IB Biology question difficult?
The hardest IB Biology questions share common features:
They present unfamiliar scenarios. You might face experimental data you've never seen before, or be asked to apply biological concepts to an unknown species.
They require synthesis of knowledge from a range of topics. For example, a genetics question might also draw on knowledge of evolution, statistics, and ethical considerations.
They involve complex data interpretation. You'll need to analyse multiple graphs, spot patterns, calculate values and explain what the data actually means in biological terms.
Command terms matter. "Describe" wants you to state what happens. "Explain" requires you to say why it happens. "Evaluate" requires you to weigh up strengths and limitations. Using the wrong approach will cause you to lose marks.
They test higher-level assessment objectives. Assessment objective 3 (AO3) assesses skills of analysis, evaluation and knowledge synthesis. This objective requires higher-level cognitive skills, such as interpreting data, weighing evidence, and forming reasoned conclusions.
How the IB Biology exam is structured
Starting from 2025, Biology students will take two external exams.
Component | Level | Duration | Total Mark | Weighting | Structure |
Paper 1 | SL | 1 hour 30 minutes | 55 marks | 36% | 30 multiple choice questions + 4 data-based questions. |
HL | 2 hours | 75 marks | 36% | 40 multiple choice questions + 4 data-based questions. | |
Paper 2 | SL | 1 hour 30 minutes | 50 marks | 44% | Section A (data / short answer questions) + Section B (1 of 2 extended response questions) |
HL | 2 hours 30 minutes | 80 marks | 44% | Section A ((data / short answer questions) + Section B (2 of 3 extended response questions) |
In addition to the external exams, the Internal Assessment (Scientific Investigation) contributes 20% of your final grade. It's assessed by your teacher and moderated by the IB.
Examples of hard IB Biology questions
Let's look at some examples of tricky IB Biology questions. We will consider what makes them challenging and how to tackle each question.
Question 1 – Protein structure
Explain the relationship between the amino acids present and the structure of globular proteins.
[3 marks]
Mark scheme:
the sequence of amino acids determines the tertiary structure of a protein; [1]
tertiary structure is the folding of a polypeptide chain; [1]
R groups of amino acids can be polar or non-polar; [1]
the protein folds due to interaction with water/the aqueous environment; [1]
the protein folds due to R group interactions; [1]
example of R group interaction, e.g. H / covalent / ionic bond / disulphide bridges; [1]
Why it's hard: This question looks simple, but it expects you to use precise terminology, e.g. “tertiary structure” and “polypeptide”. You also need to show understanding of R-group chemistry and how R groups might interact with the environment. Many students just list levels of protein structure or talk about bonds without explaining how a specific 3D shape occurs.
Examiner tips:
Ensure that each sentence contains appropriate biological terminology
Your answer as a whole must make a clear link between amino acid sequence and tertiary structure
Question 2 – Enzyme inhibition
Toxins often act as inhibitors. Compare and contrast competitive and non-competitive enzyme inhibition.
[4 marks]
Mark scheme:
Similarities:
both slow down enzyme activity; [1]
both interact with R chains of amino acids at the surface of enzymes; [1]
Differences:
Competitive inhibitor binds to active site / has a similar shape to substrate WHILE Non-competitive binds to a site other than the active site / binds to allosteric site; [1]
With competitive inhibitor the substrate cannot bind due to blockage of active site WHILE with non-competitive substrate cannot bind due to disruption/change in shape of active site; [1]
Competitive inhibition can be reversed by increasing substrate concentration WHILE non-competitive cannot be reversed by adding substrate does not reduce inhibition; [1]
Why it's hard: “Compare and contrast” means you must give both similarities and paired differences; many students only describe each type separately or forget the similarity altogether. It’s also easy to mix up where the inhibitor binds, how it affects the active site, and how adding more substrate changes the rate.
Examiner tips:
Write separate sections on similarities and differences to keep your answer organised
Ensure that each sentence contains a reference to both types of inhibitor
Question 3 – Genome size
Discuss the evidence of the relationship between genome size and the complexity
of organisms.
[4 marks]
Mark scheme:
Evidence for the relationship
Eukaryote genomes tend to be larger than prokaryote genomes; [1]
Evidence against the relationship
Most DNA sequences in higher eukaryotic genomes are non-coding; [1]
Introns occur within eukaryotic genes; [1]
There is no relationship between genome size and complexity within the eukaryotes; [1]
Example given, e.g. Amoeba proteus genome 100x larger than Homo sapiens genome; [1]
Why it's hard: The challenge here is the command term “discuss”; you’re not being asked to state a simple relationship, but to weigh up evidence for and against. Many students may fail to present both sides, or may not include examples to back up their arguments.
Examiner tips:
Aim to include evidence or arguments both for and against
Use your biological knowledge to back up your ideas
Include examples from real life
At Save My Exams we have a full range of exam questions split into topics so you can track your progress through each one.
How IB examiners award marks
Having seen what makes some IB Biology questions so demanding, it is now important to understand how examiners award marks. This will help you to focus each answer on the specific points that will be credited.
Make sure that you:
hit specific marking points. Examiners award marks for statements that match marking points in the mark scheme. You should aim to write the same number of points as there are marks available, and each sentence should contain a creditworthy idea.
use precise biological terms. Where a technical term exists, use it; vague wording risks losing marks that would be awarded for precise terms.
avoid contradictions. A correct point can lose its mark if you later contradict it. In longer answer questions, or those that contain a list of ideas, read your answer through to check that all your statements agree with each other and with your main argument.
show every step in calculations. If you slip up in an early calculation or data value, you can still earn follow-through marks by using that value correctly later. Always show your working in complex data-based questions.
structure longer answers for easy marking. Extended responses are still marked point-by-point. Use short paragraphs, each of which addresses one idea from the question, so every relevant point is easy for the examiner to find and reward.
link unfamiliar scenarios to core ideas. The toughest questions often give strange contexts or combine topics. To gain marks, keep asking: “Which biological idea is this really about?” and then apply that biology to the new situation.
write clearly for the quality mark. One extra mark in extended response questions comes from clarity and focus. Answer the exact question, avoid repetition and irrelevant side-notes, and organise your answer so it can be understood on a single read-through.
Strategies for answering challenging IB Biology questions
You now know what makes IB Biology questions demanding and how examiners award marks; the next step is to decide how you will handle those questions in the moment, when they look unfamiliar or overwhelming. Consider the strategies listed below.
Strategy | When and how to use it |
Pause and decode the question | Use this as soon as a question makes you hesitate.
|
Match your answer to the command term | When you read a question, underline the command term. As you write, check that each sentence matches this requirement; if the term is “explain”, then every main point should have a clear “because…” or “this leads to…” link, and if it is “evaluate”, you should deliberately include both positives and negatives. |
Consider the core biology behind any complex novel contexts | When a question has a long stem or a strange context, don’t allow this to distract or panic you; ask yourself “which part of the syllabus is this really about?” Identify whether it is, for example, enzyme activity, gas exchange or genetics, then draw on your knowledge of this topic. |
Build explanations as short chains | Use this for “explain” and “suggest” questions. Write in small, logical steps: statement → because → therefore. For example, “Rate decreases because enzymes denature at high temperature, therefore fewer active sites are available for successful collisions.” This makes your reasoning easy to follow and reduces gaps in the argument. |
Manage your time carefully | Across both papers you have roughly 1.5–2 minutes per mark. If you are finding a particular question especially challenging and feel as though you are getting stuck, it is often a good idea to move on and come back to it later so that you don’t run out of time. |
These strategies only become reliable in the exam if you have already used them many times in practice. Working through past papers under timed conditions trains you to decode questions quickly and to always formulate answers that match the requirements of official mark schemes. Over time, the patterns in difficult questions become familiar, and your strategies will turn into automatic routines.
At Save My Exams we have put together full mock papers for you to get to grips with and experience the feel of a real paper.
Frequently Asked Questions
Which topics have the hardest questions in IB Biology?
Some areas of IB Biology are more likely to generate difficult questions because they involve long, multi-step mechanisms that must be explained accurately. Topics such as photosynthesis, cellular respiration and neurobiology require you to keep track of detailed processes and use precise terminology, so small gaps in understanding can quickly lead to lost marks.
Other topics are challenging because they lend themselves to questions that lean heavily on application and data skills. Evolution and ecology questions often ask you to apply principles to unfamiliar scenarios and to interpret data. In these areas, the difficulty comes less from remembering facts and more from applying ideas correctly to new situations.
Using our topic questions, you can track progress and pick out the topics that you need more revision in. You can then hop over to our in-depth revision notes that follow your syllabus so you can improve on your understanding.
Are HL questions always harder than SL?
HL students cover additional content that SL students don’t, but the questions can be just as demanding at both levels. The main difference is breadth: HL has more material, so questions can draw on a wider range of ideas, but the questions themselves are not necessarily more complex or challenging than SL.
We have a full range of resources available for each course so you can find exactly what you need to support your learning and revision:
What's the best way to practice for difficult questions?
The best way to get better at difficult IB Biology questions is to practise actively. Test yourself without looking at your books, spend regular time on past papers, and go through mark schemes carefully to see exactly why marks are awarded.
Focus your effort on topics or question types where you lose marks most frequently, rather than revising your favourites on a loop, and use study groups or discussions with classmates to build your confidence and discuss best practice.
How do I know If I'm writing a level 7 answer?
Level 7 answers are accurate, precise and clearly written. Every statement must be scientifically correct, and should use proper biological terminology. Your answer should flow logically, with each paragraph developing one clear idea before moving on, and it should address the exact question rather than everything you know about a topic.
When you mark your practice answers against official mark schemes, you’re in level 7 territory if you’re consistently scoring around 80% or more of the available marks.
Final thoughts
The hardest IB Biology questions reward thinking, not just memorising. They test whether you can apply concepts, interpret data, and communicate scientific ideas clearly.
With consistent practice and the right strategies, you can master even the trickiest questions. Review past papers regularly, pay attention to command terms, structure your extended responses clearly, and practice thinking like an examiner.
Every difficult question you tackle will build your confidence and sharpen your exam technique; the more you practice, the more patterns you'll recognise and the easier these questions will become.
You've got this. Now get practising.
Explore Our IB Biology Revision Resources
References
Biology Higher and Standard Level Specimen Papers 1A, 1B and 2 (opens in a new tab)
Comprehensive Guide to IB Biology Paper 1 and Paper 2 (opens in a new tab)
IB Biology Test Prep - Biology for Life (opens in a new tab)
DP Biology: The Exams (opens in a new tab)
Biology Updates - International Baccalaureate (opens in a new tab)
IB Biology Exam Guide - Mindlab International (opens in a new tab)
Complete IB Biology Guide - TutorsPlus (opens in a new tab)
Strategies to Handle Your IBDP Biology Exam - ++tutors (opens in a new tab)
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