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IB Biology Overview

The IB Biology syllabus is designed to provide a comprehensive understanding of the fundamental principles and concepts of biology. It is a two-year course of study that is typically taken by students in their final two years of high school. IB Biology equips students with the knowledge and skills to investigate the living world. This includes the study of all levels using many different approaches and techniques.

Through studying Biology, students should become aware of how scientists work with each other. While the scientific method may take on a wide variety of forms, the emphasis is on a practical approach. In addition, through the theme of the “Nature of Science”, the knowledge and skills will be put into context.

The course is divided into eight main areas:

  1. Cell biology
  2. Molecular biology
  3. Genetics
  4. Ecology
  5. Evolution and biodiversity
  6. Human physiology
  7. Nucleic acids and proteins
  8. Biotechnology and bioinformatics

The syllabus also emphasises the importance of practical work, including experimental design, data analysis, and the communication of scientific findings. Students are expected to complete a minimum of 60 hours of practical work during the course, including a range of experimental investigations and practical activities.

Assessment in the IB Biology course is based on a combination of internal and external assessments. Internal assessments include practical work and individual investigations, while external assessments include written exams and an independent research project. The course aims to prepare students for further study in biology at the university level and to develop their critical thinking, problem-solving, and experimental skills.

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IB Biology SL/HL Syllabus

IB Biology 2014 Syllabus (First assessments 2016)

For students who have taken or are taking the IB Biology assessments between 2016 – 2024, please refer to IB Biology 2014 syllabus.

Core Topics (SL/HL)

  • Cell biology
  • Molecular biology
  • Genetics
  • Ecology
  • Evolution and biodiversity
  • Human physiology

Option Topics (SL/HL)

  • Neurobiology and behaviour
  • Biotechnology and bioinformatics
  • Ecology and conservation
  • Human physiology
    (Choice of 1 out of 4)

Practical Scheme of Work (SL/HL)

  • Prescribed and other practical activities
  • Individual investigation
  • Group 4 project

Additional Topics (HL only)

  • Nucleic acids
  • Metabolism, cell respiration and photosynthesis
  • Plant biology
  • Genetics and evolution
  • Animal physiology

IB Biology 2023 Syllabus (First assessments 2025)*

You will notice some changes to IB Biology 2023’s syllabus. One major change is how the content is organised, which aims to help you understand biology in a more conceptual way. Although the syllabus may look different and have new topic titles, don’t worry because a lot of the biology content is still the same as 2014’s syllabus. In fact, the 2023 syllabus contains approximately 5% less content than the 2014 syllabus.

Other changes include the removal of the option topics (neurobiology and behaviour, biotechnology and informatics, ecology and conservation and human physiology). From the current four options some of the content was incorporated into the course at either standard level or higher level.

* The new DP biology course will be launched in February 2023 for first teaching in August 2023. First assessment will take place in May 2025.

Core Topics (SL/HL)

  • Unity and diversity
    Water, Nucleic acids, Cell structure, Diversity of organisms, Evolution and speciation, Conservation of biodiversity
  • Form and function
    Carbohydrates and lipids, Proteins, Membranes and membrane transport, Organelles and compartmentalization, Cell specialization, Gas exchange, Transport, Adaptation to environment, Ecological niches
  • Interaction and interdependance
    Enzymes and metabolism, Cell respiration, Photosynthesis, Neural signalling, Integration of body systems, Defence against disease, Populations and communities, Transfer of energy and matter
  • Continuity and change
    DNA replication, Protein synthesis, Mutations and gene editing, Cell and nuclear division, Water potential, Reproduction, Inheritance, Homeostasis, Natural selection, Sustainability and change, Climate change

Experimental Programme (SL/HL)

  • Practical work
  • Collaborative sciences project
  • Scientific investigation

Additional Topics (HL only)

  • Unity and diversity
    Origins of cells, Viruses, Classification and cladistics
  • Form and function
    Muscle and motility
  • Interaction and interdependance
    Chemical signalling
  • Continuity and change
    Gene expression

Assessment Format

The IB Biology exams for both Standard Level (SL) and Higher Level (HL) consist of three papers: Paper 1, Paper 2, and Paper 3. The percentage of each chapter in the exams varies depending on the paper and level. Here is an overview:

First assessments 2016

Standard Level (SL)

External Assessment

  • Paper 1: 30 multiple-choice questions (45 minutes, 20% of final grade)
  • Paper 2: Data-based, short answer and extended response questions (1 hour 15 minutes, 40% of final grade)
  • Paper 3: Data-based, short answer and extended response questions (1 hour, 20% of final grade)

Internal Assessment

  • Individual investigation: Investigation and write-up of 6 to 12 pages (10 hours, 20% of final grade)

Higher Level (HL)

External Assessment

  • Paper 1: 40 multiple-choice questions (1 hour, 20% of final grade)
  • Paper 2: Data-based, short answer and extended response questions (2 hours 15 minutes, 36% of final grade)
  • Paper 3: Data-based, short answer and extended response questions (1 hour 15 minutes, 24% of final grade)

Internal Assessment

  • Individual investigation: Investigation and write-up of 6 to 12 pages (10 hours, 20% of final grade)

First assessments 2025

Standard Level (SL) & Higher Level (HL)

External Assessment

  • Paper 1 (SL 1.5 hours, HL 2 hours, 36% of final grade)
    Paper 1A: Multiple-choice questions
    Paper 1B: Data-based questions (four questions that are syllabus related, addressing all themes)
  • Paper 2 (SL 1.5 hours, HL 2.5 hours, 44% of final grade)
    Data-based and short-answer questions, extended-response questions

Internal Assessment

  • Scientific investigation (SL/HL 10 hours, 20% of final grade)
    The scientific investigation is an open- ended task in which the student gathers and analyses data in order to answer their own formulated research question. The outcome of the scientific investigation will be assessed through the form of a written report. The maximum overall word count for the report is 3,000 words.

Overall, the exams for both SL and HL cover all topics, but the emphasis on each topic varies depending on the level and paper. It is important for students to have a strong understanding of all topics and to practise a variety of question types to prepare for the exams.

Related Article(s)

IB Biology Syllabus Update: Comparing 2014 and 2023 Curriculum

| Biology, General IB, Internal Assessment, Other | No Comments
The IB regularly reviews and updates its curricula to ensure they align with current scientific knowledge and teaching practices. While the updated curriculum brings with it a range of topics…

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