Biology · XBI11 / YBI11

How International A level Biology works

Start here: the units, their exam codes and when you can sit them for Pearson Edexcel International AS and A level Biology.

Two qualifications in one course

International A level Biology is modular: you sit it unit by unit.

The International AS (cash-in code XBI11) is Unit 1, Unit 2, Unit 3. It is a qualification on its own.
The full International A level (cash-in code YBI11) is all 6 units: the AS units plus Unit 4, Unit 5, Unit 6.

You can bank AS results in Year 12 and add the A2 units in Year 13.

The units

Each unit has its own exam code. These are the codes your exams officer uses to enter you.

Unit	Code	Title	Level	Exam series 2026/27
Unit 1	WBI11	Molecules, Diet, Transport and Health	AS	October, January and June
Unit 2	WBI12	Cells, Development, Biodiversity and Conservation	AS	October, January and June
Unit 3	WBI13	Practical Skills in Biology I	AS	October, January and June
Unit 4	WBI14	Energy, Environment, Microbiology and Immunity	A2	October, January and June
Unit 5	WBI15	Respiration, Internal Environment, Coordination and Gene Technology	A2	October, January and June
Unit 6	WBI16	Practical Skills in Biology II	A2	October, January and June

Source: Pearson Information Manual 2026/2027, International A level

When you can sit them

Pearson runs International A level exams in January, May to June and October, but not every unit is offered in every series. Plan your units with your teacher, and always confirm entries with your exams officer: Pearson updates the manual every year.

Worked example

You finish Year 12 having sat the AS units in Biology. What can you claim?

The AS units are Unit 1, Unit 2, Unit 3.
Together they give the International AS (XBI11).

Answer: The International AS in Biology (XBI11); add the A2 units in Year 13 for the full A level (YBI11).

Key idea: International AS Biology = Unit 1, Unit 2, Unit 3 (XBI11). Full International A level = all 6 units (YBI11). Not every unit is offered in October.

Check yourself

What is the cash-in code for the full International A level in Biology?
- XBI11
- YBI11
- ZBI11
- WBI11
Show answer
YBI11. YBI11 is the full International A level; XBI11 is the International AS.
Which code is the International AS in Biology?
- YBI11
- WBI11
- QBI11
- XBI11
Show answer
XBI11. XBI11 is the International AS cash-in code.
How many units make up the full International A level in Biology?
Show answer
6. The full A level is 6 units: Unit 1, Unit 2, Unit 3, Unit 4, Unit 5, Unit 6.
In 2026/27, in which exam series can you sit Biology Unit 1 (Molecules, Diet, Transport and Health)?
- January and June only
- June only
- October, January and June
- January only
Show answer
October, January and June. Pearson's 2026/27 manual lists Unit 1 as available in: October, January and June.
Which Biology unit has the code WBI12?
- Unit 2
- Unit 1
- Unit 3
- Unit 4
Show answer
Unit 2. WBI12 is Unit 2: Cells, Development, Biodiversity and Conservation.

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Sources

Last updated 7 November 2026. Spotted a mistake? Email alevel@lifereadysociety.com.