Pearson International A Level Biology Core Practical 12: Investigate temperature effects on organism development

This core practical is part of Pearson's practical-learning programme. The method below is one defensible implementation, not a confidential instruction sheet. Centres may adapt equipment while preserving the scientific purpose, controls, measurements and safety requirements.

Aim and scientific principle

Compare a developmental response across controlled conditions while using ethical, viable and standardised biological material.

Begin by translating the title into a testable question. Identify what is deliberately changed, what is measured directly, what is calculated and what must remain controlled. Predict a relationship only after naming the mechanism. A prediction without a reason is weak; a reason without measurable variables cannot guide a practical design.

Apparatus and setup

Use approved organisms or seeds, controlled-temperature containers, measuring equipment, labels, timer and environmental monitors. Select every measuring instrument by range and resolution, not by name alone. Draw a labelled scientific setup that shows the working geometry and exactly where readings are taken. Include a control or blank when it distinguishes the target effect from drift, contamination or background response.

Before collecting results, check zero readings, calibration, leaks, alignment or sterility as relevant. Record the instrument resolution beside the first raw-data table. If a digital device displays more digits than its underlying accuracy supports, do not treat every digit as equally certain.

Method

1. Select similar starting material and allocate it randomly to treatment groups.
2. Maintain each group at its target condition while controlling food, moisture, oxygen, light and density as relevant.
3. Measure a predeclared developmental endpoint at regular intervals without unnecessary disturbance.
4. Repeat with independent groups, plot development against time or condition and discuss biological variation.

Plan the analysis before starting. This reveals whether an additional measurement is needed for a derived quantity and prevents a completed experiment from lacking a mass, length, concentration, background or calibration value. A method should be detailed enough for another trained student to reproduce, while avoiding decorative steps that do not affect validity.

Variables and controls

• Independent variable: temperature or germination condition.
• Dependent variable: development time, stage, proportion developed or enzyme-response proxy.