Practical skills: measurements and evidence

Learning objectives

• Plan controlled measurements and repeats.
• Interpret biological drawings and scales.
• Estimate uncertainty and variation.

The big idea

Good practical work links a question to a measurable variable, a suitable comparison and controlled conditions. Biological replication samples organism-to-organism variation; repeated readings of one specimen address a different source of variability.

Use clear tables, appropriate units and justified precision. Draw observations with labelled structures rather than invented detail. Consider hazards, consent and organism welfare when selecting methods; supplied images and datasets can practise analysis without collecting new biological material.

Investigate and explain

Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.

No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.

Open the interactive investigation

Check your understanding