The Scientific Method and Biological Terminology
What this domain tests
The scientific method section checks whether you can turn an observation into a testable hypothesis, design a fair experiment and use biological terminology precisely. Examiners reward correct use of variable, control, replicate and sample, and penalise vague claims that an experiment 'proves' a theory.
Designing a fair test
- Hypothesis: a testable statement or prediction, not a question.
- Independent variable: the factor you deliberately change. Dependent variable: the factor you measure, always with units.
- Controlled (fixed) variables: factors kept constant so they do not confound the result. A control is different - a treatment with no active factor, used for comparison.
- Replicates and random sampling reduce the effect of chance and bias; a larger sample makes results more reliable, not automatically more accurate.
Precision of language
- Species: a group of organisms that can interbreed to produce fertile offspring.
- Binomial name: genus plus species, e.g. Homo sapiens - genus capitalised, both italicised or underlined, species lowercase.
- Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other.
Worked example
A student investigates whether light intensity affects photosynthesis in Elodea by counting oxygen bubbles per minute. Independent variable: light intensity, altered by lamp distance. Dependent variable: bubble count per minute. Controls: temperature, hydrogencarbonate concentration, same plant, same counting time. A foil-wrapped dark control shows the bubbles are light-dependent. Reasoning: the bubble count is an indirect measure, so the conclusion must state the assumption that the bubbles are oxygen.
Traps
Confusing 'control' with 'controlled variables'; omitting units; claiming results 'prove' a hypothesis rather than support it; defining a species without 'fertile offspring'.