Introduction to IB Biology

IB Biology is one of the most popular science subjects in the International Baccalaureate Diploma Programme, chosen by thousands of students worldwide each year. Whether you’re studying at Standard Level (SL) or Higher Level (HL), mastering IB Biology requires a strategic approach that goes beyond simple memorisation.

This comprehensive revision guide will walk you through every aspect of IB Biology preparation — from understanding the syllabus structure to exam-day techniques that can help you achieve that coveted 7.

Understanding the IB Biology Syllabus Structure

Standard Level (SL) vs Higher Level (HL)

IB Biology SL covers the core topics and requires approximately 150 hours of teaching time, while HL includes additional topics and requires around 240 hours. Both levels share the same core content but differ in depth and breadth.

Core Topics (SL and HL):

• Topic 1: Cell Biology — Cell theory, ultrastructure of cells, membrane structure, membrane transport, cell division
• Topic 2: Molecular Biology — Molecules to metabolism, water, carbohydrates and lipids, proteins, enzymes, DNA structure and replication, transcription and translation, cell respiration, photosynthesis
• Topic 3: Genetics — Genes, chromosomes, meiosis, inheritance, genetic modification and biotechnology
• Topic 4: Ecology — Species, communities and ecosystems, energy flow, carbon cycling, climate change
• Topic 5: Evolution and Biodiversity — Evidence for evolution, natural selection, classification of biodiversity, cladistics
• Topic 6: Human Physiology — Digestion, the blood system, defence against infectious disease, gas exchange, neurons and synapses, hormones and homeostasis

Additional HL Topics

• Topic 7: Nucleic Acids — DNA structure and replication (HL detail), transcription and gene expression, translation
• Topic 8: Metabolism, Cell Respiration and Photosynthesis — Detailed metabolic pathways, oxidative phosphorylation, photosystems
• Topic 9: Plant Biology — Transport in xylem and phloem, growth in plants, reproduction in plants
• Topic 10: Genetics and Evolution — Meiosis detail, inheritance detail, gene pools and speciation
• Topic 11: Animal Physiology — Antibody production, movement, the kidney, sexual reproduction

Topic-by-Topic Revision Strategies

Cell Biology (Topic 1)

Cell Biology forms the foundation for everything in IB Biology. Start your revision here.

Key concepts to master:

• Draw and label prokaryotic and eukaryotic cells from memory
• Understand the fluid mosaic model thoroughly
• Be able to explain active and passive transport with examples
• Know the stages of mitosis and their significance

Study tip: Create comparison tables for prokaryotic vs eukaryotic cells, and for different types of membrane transport. Visual learners should practice drawing cell diagrams repeatedly until they can reproduce them under timed conditions.

Molecular Biology (Topic 2)

This is often the most challenging core topic. Focus on understanding processes rather than memorising steps.

Critical areas:

• Enzyme kinetics — understand competitive and non-competitive inhibition graphs
• DNA replication — be able to explain the semi-conservative model with reference to Meselson-Stahl
• Transcription and translation — know the roles of mRNA, tRNA, and ribosomes
• Distinguish between aerobic and anaerobic respiration

Common mistakes to avoid:

• Confusing condensation and hydrolysis reactions
• Mixing up the functions of different RNA types
• Forgetting that enzymes are not consumed in reactions

Genetics (Topic 3)

Genetics questions are predictable and follow patterns. Practice is key.

Focus areas:

• Punnett squares for monohybrid and dihybrid crosses
• Sex-linked inheritance problems
• Chi-squared test calculations and interpretation
• Understanding codominance and multiple alleles (e.g., ABO blood groups)

Exam strategy: For genetics problems, always define your alleles first, then set up the cross systematically. Show all working — even if you make an error in the final answer, you can earn method marks.

Ecology (Topic 4)

Ecology connects biological concepts to real-world applications. Examiners love to test application skills here.

Essential knowledge:

• Energy flow through ecosystems (10% rule)
• Constructing and interpreting food webs
• Carbon cycle — including human impacts
• Understanding Simpson’s Diversity Index

Tip: Stay current with environmental issues. IB Biology exams frequently include data-based questions using real ecological studies.

Evolution and Biodiversity (Topic 5)

Key areas:

• Evidence for evolution (fossil record, homologous structures, molecular evidence)
• Mechanisms of natural selection with specific examples
• The binomial naming system and classification hierarchy
• Reading and constructing cladograms

Human Physiology (Topic 6)

This topic is content-heavy but highly structured. Create a system to organise your notes.

Priority areas:

• The digestive system — know specific enzymes, their sources, and substrates
• Heart structure and the cardiac cycle
• Ventilation mechanisms and gas exchange
• Nervous system — action potentials and synaptic transmission
• Hormonal regulation — especially blood glucose and thyroxine

HL-Specific Revision Tips

Metabolism and Biochemistry (Topics 7-8)

HL students must understand metabolic pathways in significantly more detail.

Focus on:

• The link reaction and Krebs cycle — know the inputs, outputs, and locations
• Oxidative phosphorylation and chemiosmosis
• Light-dependent and light-independent reactions of photosynthesis
• Gene expression regulation

Study method: Create flowcharts for each metabolic pathway. Colour-code inputs (red), outputs (green), and enzymes (blue). This visual approach helps with recall under exam pressure.

Plant Biology (Topic 9)

Often overlooked by students, but it’s a favourite of examiners.

Essential concepts:

• Transpiration and the cohesion-tension theory
• Translocation and the pressure-flow hypothesis
• Plant growth regulators (auxins, cytokinins, gibberellins)
• Photoperiodism and phytochrome

Animal Physiology (Topic 11)

Critical areas for HL:

• Muscle contraction — the sliding filament model in detail
• Kidney structure and function — including the countercurrent multiplier
• Hormonal control of the menstrual cycle
• In vitro fertilisation (IVF) and ethical considerations

Mastering IB Biology Exam Technique

Paper 1: Multiple Choice

• SL: 30 questions in 45 minutes
• HL: 40 questions in 60 minutes

Strategies:

1. Read every option before selecting an answer
2. Eliminate obviously wrong answers first
3. Be cautious with “all of the above” or “none of the above” options
4. Don’t change your first answer unless you’re certain it’s wrong
5. Manage your time — roughly 1.5 minutes per question

Paper 2: Data-Based and Extended Response

This paper tests your ability to analyse data, apply knowledge, and construct extended arguments.

Section A (Data-Based Question):

• Read the data carefully before answering
• Reference specific data points in your answers (use numbers!)
• Show calculations clearly
• State trends before explaining them

Section B (Extended Response):

• Plan your essay before writing — spend 3-5 minutes outlining
• Use correct biological terminology throughout
• Include specific examples where possible
• For 8-mark questions, aim for at least 8-10 distinct points

Paper 3: Options and Experimental Work

For the experimental question:

• Know the independent, dependent, and controlled variables
• Understand how to design a valid experiment
• Be able to identify and explain sources of error
• Know the difference between accuracy, precision, and reliability

Internal Assessment (IA) Tips

The IA accounts for 20% of your final grade. Choose your topic wisely.

Successful IA strategies:

• Pick a topic that genuinely interests you
• Ensure you can manipulate a clear independent variable
• Collect sufficient data (at least 5 different values of your IV, with 5 trials each)
• Use appropriate statistical analysis
• Be honest about limitations and suggest realistic improvements

Popular high-scoring topics:

• Effect of temperature on enzyme activity (catalase/amylase)
• Effect of light intensity on photosynthesis rate (aquatic plants)
• Allelopathy experiments
• Heart rate recovery after exercise

Creating an Effective Study Schedule

3-Month Revision Plan

Months 3-2 before exams:

• Review all core topics systematically
• Create summary notes and flashcards
• Complete topic-specific past paper questions

Month 2-1 before exams:

• Focus on HL additional topics
• Practice full past papers under timed conditions
• Review mark schemes to understand examiner expectations

Final month:

• Daily past paper practice
• Focus on weak areas identified from practice papers
• Review all diagrams and key definitions
• Practice data analysis questions

Recommended Study Resources

1. IB Biology textbook (Allott & Mindorff or Walpole)
2. Past papers with mark schemes (available from your school)
3. Online revision platforms — look for IB-specific resources
4. Flashcard apps — create your own for active recall
5. Study groups — explaining concepts to others strengthens your understanding

Common Pitfalls and How to Avoid Them

Mistake 1: Memorising Without Understanding

IB Biology rewards understanding over memorisation. Focus on why biological processes occur, not just what happens.

Mistake 2: Neglecting Command Terms

The IB uses specific command terms (outline, describe, explain, evaluate, discuss). Each requires a different level of response. “Outline” requires less detail than “explain,” while “evaluate” requires you to make a judgement.

Mistake 3: Ignoring the Syllabus Guide

The syllabus guide specifies exactly what you need to know. Use it as a checklist during revision.

Mistake 4: Skipping Diagrams

Many marks are available for correctly drawn and labelled diagrams. Practice drawing:

• Cell organelles
• The heart
• DNA replication fork
• Photosynthesis light reactions
• Nephron structure (HL)

Mistake 5: Not Practising Under Timed Conditions

Knowing the content is only half the battle. You must also be able to recall and apply it within time constraints.

How Tutopiya Can Help You Succeed in IB Biology

Preparing for IB Biology doesn’t have to be a solo journey. At Tutopiya, our experienced IB Biology tutors provide personalised one-on-one sessions tailored to your specific needs. Whether you’re struggling with HL biochemistry or need help perfecting your IA, our tutors can provide targeted support.

What Tutopiya offers for IB Biology students:

• Expert tutors with IB teaching experience
• Flexible scheduling to fit around your IB workload
• Personalised lesson plans based on your strengths and weaknesses
• Practice with past paper questions and detailed feedback
• Support with Internal Assessment planning and execution

Ready to Boost Your IB Biology Grade?

Don’t wait until exam season to get help. Book a free trial lesson with one of our IB Biology specialists today and discover how personalised tutoring can transform your understanding and confidence.

Whether you’re aiming for a 7 or simply want to feel more prepared walking into the exam hall, Tutopiya’s expert tutors are here to help you reach your full potential in IB Biology.