A biological investigation starts with a question and ends with a conclusion. In between, you state a hypothesis, control the variables, record results and interpret them.
This hub sits inside the SPM Biology subject guide. Each lesson in this chapter teaches one skill.
How do the parts connect?
Each skill feeds the next.
- The hypothesis states what you expect and gives the test a direction.
- The variables show what you change, what you measure and what you keep the same.
- The table and drawing record what happens, with headings that match the variables.
- Observation, inference and conclusion turn the record into an answer to the hypothesis.
If the hypothesis is vague, the variables become unclear and the conclusion has nothing to confirm.
A short example: yeast and temperature
Original question: does temperature affect how fast yeast makes carbon dioxide in a sugar solution?
- Hypothesis: the higher the temperature up to 35 °C, the more bubbles of carbon dioxide yeast produces.
- Variables: change the temperature, measure the bubbles in two minutes, keep the yeast mass and sugar volume the same.
- Table: temperature in the first column, bubble count in the second.
- Conclusion: if 35 °C gives the most bubbles, the hypothesis is accepted for the temperatures tested.
The same small experiment passes through every skill.
Who should start where?
| Your situation | Start with |
|---|---|
| Your hypothesis is a question or a guess | Writing a testable hypothesis |
| You mix up what to change and what to measure | Identifying variables and controls |
| Your tables or drawings lose marks | Planning tables and biological drawings |
| You write inferences as observations | Distinguishing observation, inference and conclusion |
For explanation skills that follow, see from biological recall to causal explanation. Test the chapter with the practice set.
If you want a teacher to guide you through each skill, see online one-to-one Biology tuition.