Scientific Method Notes: Questions, Evidence, and Scientific Inquiry

Biology Foundations and Lab Skills Teaching Resources · High school biology; AP extensions where noted.

Biologists investigate questions using observations, comparisons, experiments, models, and existing data. A classroom sequence can help organize work, but research does not always follow one fixed list of steps. Scientists revisit ideas when evidence, methods, or questions change.

Learning goals and prerequisites

Students will distinguish an observation, hypothesis, prediction, and conclusion; identify what evidence could challenge an explanation; and recognize both experimental and observational research. No prior laboratory experience is required. Materials: paper and the example below.

Terms with a biological example

Observation: a recorded feature or measurement. “Seedlings beside the window are taller” describes a pattern; it does not yet explain its cause.
Question: a focused problem that evidence could help answer. “How does daily light duration affect seedling height after ten days?” is more testable than “Which plant is best?”
Hypothesis: a proposed explanation. For example, differences in light exposure may contribute to the height difference. Other explanations remain possible.
Prediction: an expected observation under specified conditions if an explanation is useful. State what would be measured, when, and compared with what. A predicted direction requires a biological reason; less light does not always mean a shorter seedling.
Evidence: observations analyzed in relation to the question, with attention to uncertainty and alternative explanations.
Conclusion: a statement explaining what the evidence supports and where the inference stops.

Plan a fair comparison

In a simple experiment, change the selected factor and keep other relevant conditions comparable. Define the response before collecting data. Use independent experimental units, repeat the comparison where practical, and assign treatments fairly. Measuring one plant ten times improves information about that plant; it does not create ten independent plants.

In an observational study, a researcher may measure variables without assigning a treatment. A relationship between two variables alone does not establish that one caused the other. Confounding factors and the sampling method matter.

Work through the example

List two possible explanations for the window-side pattern.
Choose one question and define how height will be measured.
Describe a comparison that separates light duration from water supply as far as the classroom setup allows.
Explain why several plants under each condition are more useful than a single plant per condition.
Write a result that would make you reconsider your explanation.

Check understanding

Must a hypothesis be correct? No. It must be open to examination with evidence. An unsupported prediction can still lead to useful learning. Does a hypothesis turn into a law after enough experiments? No. Hypotheses, theories, and laws serve different roles; they are not levels on a ladder. Must all biology involve a controlled experiment? No. Field observations and comparisons can also provide evidence.

Teaching note: Ask students to justify revisions rather than reward a predicted result. For AP extension, discuss random assignment, independent replication, and the difference between evidence for a pattern and evidence for a mechanism.