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Assessment
How Pearson Edexcel International A Level Biology is assessed
The International AS is Units 1, 2 and 3 and is half of the International A Level, which adds Units 4, 5 and 6. Each unit is a separate exam, available in January, June and October, so you can take units as you go or all at the end. Unit 5 includes questions on a scientific article released before the exam.
Specification XBI11/YBI11 (Issue 2), first examined in 2019. Pearson has announced new specifications for first teaching in September 2027, which these details don’t cover.
International AS (Units 1–3)
Unit 1 (WBI11): Molecules, Diet, Transport and Health
Multiple choice, short and open answers, calculations and extended writing
- Time
- 1 h 30 min
- Marks
- 80
- Weight
- 40% of IAS, 20% of IAL
Unit 2 (WBI12): Cells, Development, Biodiversity and Conservation
Multiple choice, short and open answers, calculations and extended writing
- Time
- 1 h 30 min
- Marks
- 80
- Weight
- 40% of IAS, 20% of IAL
Unit 3 (WBI13): Practical Skills in Biology I
Written paper on planning, carrying out and analysing practical work
- Time
- 1 h 20 min
- Marks
- 50
- Weight
- 20% of IAS, 10% of IAL
International A Level adds Units 4–6
Unit 4 (WBI14): Energy, Environment, Microbiology and Immunity
Multiple choice, short and open answers, calculations and extended writing, with some synoptic questions
- Time
- 1 h 45 min
- Marks
- 90
- Weight
- 20% of IAL
Unit 5 (WBI15): Respiration, Internal Environment, Coordination and Gene Technology
Multiple choice, short and open answers, calculations and extended writing, with some synoptic questions
- Time
- 1 h 45 min
- Marks
- 90
- Weight
- 20% of IAL
Unit 6 (WBI16): Practical Skills in Biology II
Written paper on planning, carrying out and analysing practical work
- Time
- 1 h 20 min
- Marks
- 50
- Weight
- 10% of IAL
There is no coursework or practical exam. Practical skills are tested in the written Units 3 and 6, and questions in the other units draw on the core practicals. Biology has 18 core practicals.
From the official Pearson Edexcel syllabus, checked October 2026. Read the syllabus
Syllabus content
What’s on the Pearson Edexcel International A Level Biology syllabus
International AS
- Molecules, transport and health
- Membranes, proteins, DNA and gene expression
- Cell structure, reproduction and development
- Plant structure and function, biodiversity and conservation
International A Level
- Energy flow, ecosystems and the environment
- Microbiology, immunity and forensics
- Respiration, muscles and the internal environment
- Coordination, response and gene technology
Where marks are lost
Common Pearson Edexcel International A Level Biology mistakes
Mixing up transcription and translation.
Transcription copies DNA into mRNA in the nucleus. Translation uses the mRNA to build a polypeptide at a ribosome.
Treating correlation as proof of cause.
A correlation shows two variables change together. To show cause, you need a controlled experiment.
Answering Unit 5 from the article alone.
Use the pre-release article as context, but answer with the biology in the specification. Quoting the article isn’t enough.
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