Edexcel IAL Biology Unit 6 — Practical Skills in Biology II
Unit 6 (WBI16/01) is the A2 practical paper: 50 marks in 1 h 20 on planning, evaluating and analysing investigations drawn from the core practicals of Units 1, 2, 4 and 5. No new theory — but the most predictable marks in the whole qualification if you know the practicals.
Solved Unit 6 past papers See the A2 courseRevise Unit 6 with Mr Hosni
What examiners actually reward in Unit 6 answers — the 'Describe' marks students leave on the table.
This practical appears in nearly all Unit 3 and Unit 6 IAL Biology exams
Must-know practical
This practical already came 6 times before in the IAL Biology unit 3 exam
Same skills, Unit 3
How to prepare for the IAL Unit 3 Biology Exam?
10,600 views · same method
What the WBI16 paper actually tests
Seventeen papers, 310 question parts, 2020 to 2026. Ecology of a habitat (CP 11) is the single most examined practical at 17% of marks. Respiration rate and RQ with a respirometer (CP 16) and the rate of photosynthesis (CP 10) follow at 8–9% each. But the largest share — 38% — comes from investigations that are not core practicals at all: an unfamiliar method on a familiar principle. That is the point of the paper. The skills are fixed; the context changes.
"Describe" is the top command word, followed by "Explain" and "Calculate". Students lose marks here by writing what they would do rather than a numbered method with variables, control, measurement and repeats stated explicitly.
Share of marks by topic
17 papers · 310 question parts · 850 classified marks · 2020–2026
Least examined
Command words, most to least common
Describe (97), State (42), Calculate (39), Suggest (32), Explain (22), Draw (22).
What this means for you
Other practicals, Ecology of a habitat and Respiration rate and respiratory quotient carry 64% of the marks. Revise them first, then work down the list. Every solved question below is written in the mark-scheme words the examiner ticks.
The nine core practicals Unit 6 is built on
CP 10 photosynthesis rate in an aquatic plant; CP 11 ecology of a habitat; CP 12 temperature and development; CP 13 microbial growth in liquid culture; CP 14 antibiotics and bacteria; CP 15 respiration in yeast with a redox indicator; CP 16 respirometer and RQ; CP 17 exercise and spirometer traces; CP 18 amylase in germinating grains. Any of CP 1–9 from Units 1 and 2 can also appear. For each one, be able to write: independent variable, dependent variable and how it is measured, three controlled variables and how, the calculation, the two main sources of error and the improvement for each.
Planning: what the question wants
Choose apparatus with detail — range, resolution, dimensions. State a null hypothesis. Name the dependent, independent and controlled variables and say how each is controlled. Mention calibration where a meter is involved. Decide whether repeats are appropriate and why. Identify safety and ethical issues, especially with living organisms, and say how you deal with them. Explain how the data will be used.
Implementation and analysis: where marks are won
Implementation questions give you someone else's results and ask what is wrong: significant figures inconsistent in a table, units missing or wrong, an anomaly off the line, too few readings across too narrow a range. Analysis questions ask you to tabulate with units, calculate to the right number of significant figures, plot on an appropriate scale — sometimes logarithmic — read a gradient from a large triangle, describe the trend and suggest realistic modifications. Every one of these is a mark you can secure before you open the paper.
How to revise Unit 6 in the right order
- Write the nine A2 core practicals as one-page methods in the format above.
- Do the same for CP 1–9.
- Work through the solved WBI16 papers; for every "Describe a method" question, compare your numbered steps with the model answer line by line.
- Practise the maths: significant figures, percentage change, gradients.
- Use the checklist below to confirm every skill statement is covered.
Unit 6 specification checklist
Core practicals and the three assessed skill sets, condensed point by point. Tick as you master each — progress is saved on this device.
The nine core practicals Unit 6 is built on
- CP 10 Effect of light intensity, wavelength, temperature and CO₂ availability on the rate of photosynthesis (aquatic plant)
- CP 11 Ecology of a habitat — quadrats, transects, abiotic factors, distribution and abundance
- CP 12 Effect of temperature on the development of organisms (seedling growth, brine-shrimp hatch rate) with ethical use of organisms
- CP 13 Rate of growth of microorganisms in liquid culture, safely and ethically
- CP 14 Effect of different antibiotics on bacteria
- CP 15 Respiration in yeast using a redox indicator (artificial hydrogen carrier)
- CP 16 Respirometer: rate of respiration and RQ of germinating seeds or small invertebrates
- CP 17 Effect of exercise on tidal volume, breathing rate, minute ventilation and O₂ consumption from spirometer traces
- CP 18 Amylase production in germinating cereal grains
- + Units 1–2 Any core practical from Units 1 and 2 (CP 1–9) can also be examined — Unit 6 is synoptic across all topics
Planning — what the question asks you to do
- Apparatus Choose the most appropriate apparatus with detail — range, resolution, relevant dimensions (for example the quadrat area)
- Hypothesis Formulate a null hypothesis
- Variables Identify the dependent, independent and controlled variables and state how each is controlled to make a fair test
- Calibration Discuss instrument calibration — does a meter read zero before use?
- Measurement Describe how each variable is measured with the right instrument and technique; decide whether repeats are appropriate
- Safety & ethics Identify health-and-safety issues and any ethical issues with living organisms, and how to deal with them
- Data use Explain how the collected data will be used
Implementation and measurements — evaluating a method
- Improvements Suggest how the experiment could be improved, including additional apparatus to reduce error
- Readings Comment on the number and range of readings taken
- Significant figures Identify and round incorrect figures in a results table; identify and amend wrong units
- Anomalies Identify and check a reading inconsistent with the others — a point off the line
Analysis — presenting and interpreting data
- Tables Explain how data should be tabulated, with units
- Calculations Perform calculations to the correct number of significant figures
- Graphs Plot on an appropriate scale with units — possibly logarithmic; use correct units throughout
- Trends Comment on the trend or pattern; find the relationship between variables or a constant from the graph, for example a gradient from a large triangle
- Modifications Suggest realistic modifications to reduce error and improve the experiment
Condensed from the Pearson Edexcel International Advanced Level in Biology specification, Issue 2 (2018 qualification, units WBI11–WBI16). Always check the full wording in the official specification.
Unit 6 — FAQ
Is there a separate practical exam for IAL Biology Unit 6?
No. Unit 6 is a written paper. It assesses practical skills through questions about planning investigations, evaluating methods and analysing data from the core practicals of Units 1, 2, 4 and 5.
Which practicals come up most in WBI16?
Across 2020–2026 papers, ecology of a habitat (CP 11) is the single most examined practical at about 17% of marks, followed by respiration rate and RQ (CP 16) and photosynthesis rate (CP 10). Around 38% of marks come from unfamiliar investigations that test the same skills in new contexts.
How do I revise for a practical paper?
Learn each core practical as a method, not a memory: independent and dependent variables, the three controls, the measurement, the calculation and the two main sources of error. 'Describe' is the top command word in Unit 6, so practise writing methods in numbered steps.
How much is Unit 6 worth?
50 raw marks, 60 UMS, 10% of the full International A Level. It is also part of the 90%-of-A2 UMS requirement for an A*.
About this page
About Edexcel IAL Biology Unit 6 (WBI16/01). Unit 6, Practical Skills in Biology II, is one of the three IA2 units of the Pearson Edexcel International Advanced Level in Biology (YBI11), examined in January, June and October. It is a 50-mark, 1 h 20 written paper worth 10% of the full IAL. The topic checklist on this page is a condensed study companion to the official specification (Issue 2); the marks analysis is Chem Bio's classification of every question part in 17 WBI16 papers from 2020 to 2026 (310 parts, 850 marks) by topic, command word and difficulty. Written by Hosni Showike, Head of Science, 21 years teaching Edexcel IAL Biology.
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Every WBI16 question since 2020, solved for the marks
Point-by-point model answers in mark-scheme language, the notes written on this specification, and WhatsApp support from Mr Hosni until exam day.
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