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Biology · Chapter 2: The Scientific Method (Solving a Biological Problem)
Steps of the Scientific Method
The scientific method step by step: observation, question, hypothesis, deduction, experiment, results and conclusion, with an example and a flow chart.
Key termRememberExampleWatch out
01Concept
Biologists do not guess answers. They follow a careful, step-by-step way of solving problems called the scientific method. It is an organised way of finding answers to questions about nature by observing, testing and checking.
The same steps are used to find the cause of a disease, test a new medicine or find out why the leaves of a plant are turning yellow.
The steps
| Step | What the biologist does | Example: yellow leaves on a lemon plant |
|---|---|---|
| 1. Observation | Notices something using the senses or instruments | The leaves of a lemon plant in the school garden are turning yellow. |
| 2. Question | Asks a clear question about it | Why are the leaves turning yellow? |
| 3. Hypothesis | Suggests a possible answer that can be tested | The plant is not getting enough nitrogen from the soil. |
| 4. Deduction | Works out what should happen if the hypothesis is true: "If…, then…" | If the plant lacks nitrogen, then adding a nitrogen fertiliser will make new leaves green. |
| 5. Experiment | Tests the deduction, using a control group | Give fertiliser to some plants and none to others; keep everything else the same. |
| 6. Results | Records what happens, as tables and graphs | New leaves on fertilised plants are green; the others stay yellow. |
| 7. Conclusion | Decides whether the hypothesis is accepted or rejected | The hypothesis is accepted: the plants lacked nitrogen. |
Sharing the results
At the end, scientists publish their work in scientific journals so that other scientists can repeat the experiment and check it. A result that others cannot repeat is not accepted.
02Virtual Lab
Try this topic for yourself in the virtual lab. It opens on its own page with steps, tasks and questions.
03Real World Examples
Testing a new wheat variety
Before a new wheat seed is given to farmers in Punjab and Sindh, research institutes such as the National Agricultural Research Centre (NARC) in Islamabad grow it beside ordinary wheat for several seasons and compare the yield. That is the scientific method at work.
Medicines
Every medicine sold in a pharmacy was first tested on volunteers: one group got the medicine and a control group got a dummy tablet (placebo). Only if the medicine worked better was it approved.
Dengue in Lahore and Karachi
Health workers observed that dengue cases rise after the monsoon. Testing the idea that standing water breeds the Aedes mosquito led to campaigns to empty water from tyres, pots and coolers.
04Practice Questions
Try to answer in your own words first, then open the model answer.
Short questions
Q1.Define the scientific method.Show answer
Answer
The scientific method is an organised, step-by-step way of finding answers to questions about nature by observation, hypothesis and experiment.
Q2.List the steps of the scientific method in the correct order.Show answer
Answer
- Observation
- Question (recognising the problem)
- Hypothesis
- Deduction
- Experiment
- Results (data)
- Conclusion
Q3.What happens if the results of an experiment do not support the hypothesis?Show answer
Answer
The hypothesis is rejected. The scientist makes a new hypothesis and tests it with new experiments.
Q4.Why do scientists publish their results?Show answer
Answer
So that other scientists can repeat the experiment and check the results. A result is accepted only when others get the same answer.
Q5.A student sees that the bread in her kitchen grows mould faster in the monsoon. Write a hypothesis and a deduction for this observation.Show answer
Answer
- Hypothesis: mould grows faster when the air is humid (moist).
- Deduction: if mould grows faster in humid air, then bread kept in a damp box will grow mould sooner than bread kept in a dry box.
Long questions
Q6.Describe the steps of the scientific method with the help of an example.Show answer
Answer
Example: the leaves of a lemon plant are turning yellow.
- Observation: the leaves are turning yellow.
- Question: why are the leaves turning yellow?
- Hypothesis: the plant is short of nitrogen.
- Deduction: if it lacks nitrogen, then nitrogen fertiliser will make new leaves green.
- Experiment: some plants get fertiliser (experimental group), others get none (control group). Water, light and soil are kept the same.
- Results: new leaves on fertilised plants become green; the others stay yellow.
- Conclusion: the hypothesis is accepted. If the results had been different, a new hypothesis would be made and tested.