Planning an investigation

Planning an investigation is a fundamental practical skill in Biology, requiring students to design well-structured experiments to address specific scientific questions. This process is crucial for developing a deep understanding of the subject and is heavily assessed in examinations, often contributing a significant portion of marks.

• Defining the Problem and Hypothesis

  • Begin by clearly stating what you are trying to find out. This often involves making an observation and asking "why" or "how" it happens.

  • Formulate a prediction or hypothesis, which is a specific, testable statement based on a theory, about what will happen in the experiment. A good hypothesis must be quantifiable, testable, and falsifiable.

• Identifying and Controlling Variables

  • Variables are quantities that can change. You typically change one variable and measure its effect on another.

  • Independent Variable: The variable that you change or select.

  • Dependent Variable: The variable that you measure; it changes as a result of the independent variable.

  • Controlled/Standardized Variables: All other variables that could affect the results must be kept constant. This ensures that only the independent variable is affecting the dependent variable, making results valid.

• Controls in Experiments

  • Negative controls are used to ensure that only the independent variable is causing the observed effect. For example, in a photosynthesis experiment, a control in the dark should show no photosynthesis.

  • Placebos serve a similar function in human drug trials, being an inactive substance that looks like the drug being tested.

• Ensuring Reliability and Accuracy

  • Repeats: Taking several repeat measurements and calculating the mean reduces the effect of random error, making results more precise. Repeatable data means similar results are obtained each time, increasing the likelihood of reproducibility by other scientists.

  • Sample Size: A large sample size reduces the likelihood of results being due to chance, making them more reliable and generalizable to the whole population.

  • Measurements: Decide what to measure, how often, and use appropriate apparatus sensitive enough for the changes being observed. Measurements should be accurate and precise, accounting for human interpretation and instrument limitations.

• Methodology and Data Recording

  • Describe a logical sequence of steps for the investigation. Diagrams can often help explain apparatus setup.

  • Record data in a well-structured table with appropriate headings, units, and consistency in significant figures.

• Safety and Ethical Considerations

  • Conduct a risk assessment to identify dangers, who is at risk, and how to reduce those risks. This includes standard precautions like lab coats and goggles, and specific measures like aseptic techniques for microorganisms.

  • Consider ethical issues, particularly when working with living organisms (e.g., animals, human participants). This involves balancing potential benefits against moral concerns about distress, consent, and the use of life.

• Evaluation and Improvement

  • Planning also involves thinking about how to improve experiments to make results more reliable or conclusions more valid. This can involve suggesting better control of variables, more precise measurements, or larger sample sizes.

Students are expected to apply these planning principles to various investigations, including enzyme reactions, osmosis, photosynthesis, and respiration.