Designing controlled biological investigations

≈ 48 min

Designing controlled biological investigations

A controlled investigation tests a focused question by changing one independent variable and measuring a dependent variable while keeping important conditions constant. A hypothesis predicts a relationship that could be supported or not supported. Controls provide comparison, replication estimates variation, and safety or ethics shape what can be done. A fair test is not one that guarantees an expected result; it is one that gives a credible chance to detect a real pattern.

Work it through

To test whether light intensity affects pondweed oxygen production, vary lamp distance, measure bubbles or oxygen over a fixed time, keep water temperature and plant length similar, repeat each distance and record anomalies.

Mastery target

Write a testable question, identify variables and explain one control, one repeat and one limitation.

What is the independent variable in an investigation?

The factor deliberately changed

The result measured

Every condition kept the same

The conclusion

Name the key biological term from Designing controlled biological investigations: enter the term that best fits the explanation and visual model.

Why repeat measurements at each light intensity?

To estimate variation and make the pattern more reliable.

To ensure identical results.

To change the independent variable twice.

To avoid recording data.

Which statement corrects a common misunderstanding in Designing controlled biological investigations?

Correct: Changing several variables together prevents you from knowing which variable produced an observed difference.

A single observation is enough to prove every biological claim.

Scientific terms are interchangeable whenever they sound similar.

A process always has exactly the same result in every environment.