Define a practical problem and prediction
Translate an investigation context into a testable prediction linked to a biological hypothesis and measurable variables.
Cambridge International Biology 9700, 2028–2030. Paper 5 assesses planning, analysis and evaluation. These original practice tasks are not Cambridge exam questions or mark schemes.
Before you begin
- Use biological vocabulary and basic calculations from the AS Biology course. Follow your school laboratory rules and teacher instructions for all practical work.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What should a practical prediction connect?
What you will learn
- State a directional or non-directional prediction with a biological reason.
- Identify independent, dependent and key standardised variables.
- Sketch an expected relationship when useful.
Link the prediction to the idea
A prediction states what is expected to happen to the dependent variable when the independent variable changes. Link it to an underlying biological hypothesis; do not simply restate the topic.
Identify the independent and dependent variables precisely. Use an operational definition for the measured response, such as gas volume per minute or time to a stated colour endpoint.
Show expected shape
A sketch graph can make a prediction clearer. Label both axes and show the expected direction or shape, such as an initial increase followed by a plateau.
Separate a prediction from the result. A plan predicts a pattern; only measured evidence can support or challenge it.
Pause and explain
Which is a testable prediction?
Worked example
How might increasing substrate concentration affect enzyme rate when enzyme concentration is fixed?
Show the worked solution
- State the independent and dependent variables.
- Predict the initial pattern and possible plateau.
- Link the plateau to enzyme active sites becoming occupied.
Answer Prediction: increasing substrate concentration will initially increase enzyme rate, then the rate will approach a plateau when enzyme active sites are occupied. The relationship is substrate concentration versus rate, with enzyme concentration held constant.
From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write a prediction for how increasing light intensity affects oxygen production by an aquatic plant.
Give me a hint
State the expected response and one condition to hold constant.
Compare my reasoning
- Link light intensity to photosynthesis rate.
- Predict oxygen production per unit time.
- Name an appropriate controlled condition such as temperature.
As light intensity increases, oxygen production per unit time is expected to increase until another factor becomes limiting; temperature and carbon dioxide availability should be standardised.
Look for these in your work
- Directional prediction
- Measurable response
- Limit or control included
A question asks whether two pH conditions affect enzyme activity differently. Give a non-directional hypothesis and measurable outcome.
Give me a hint
A hypothesis can predict a difference without choosing which condition is greater.
Compare my reasoning
- State that pH is the independent variable.
- Define activity, for example rate or time to endpoint.
- Predict that the measured outcome differs between pH conditions.
Hypothesis: enzyme activity differs between the two pH conditions, measured using a consistent rate or time-to-endpoint method.
Look for these in your work
- Variables clear
- Measurable outcome
- Non-directional prediction
A transfer context provides only an unfamiliar apparatus diagram. What does the prediction still need?
Give me a hint
Use the same logical structure even in a new context.
Compare my reasoning
- Identify the controllable change.
- Identify what the apparatus can measure.
- Predict how the response changes and why.
Identify the independent variable, the response the apparatus measures, and a biologically reasoned prediction linking them.
Look for these in your work
- Method transfers
- Reasoning based on supplied context
Common mistakes
- Writing a prediction without naming variables.
- Claiming a result before data are collected.
- Leaving out the biological reasoning that links variables.
What can you explain now?
What should a practical prediction connect?
Compare with the explanation
A change in the independent variable to an expected dependent-variable response
That makes the expected relationship testable.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
What turns a biological statement into a useful practical prediction?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.