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Biology · Chapter 2: The Scientific Method (Solving a Biological Problem)
Observation and Questions
Qualitative and quantitative observations, how instruments help biologists, and how to turn an observation into a testable scientific question.
Key termRememberExampleWatch out
01Concept
Every scientific discovery begins with an observation. An observation is information gathered by using our senses (sight, hearing, touch, smell and taste) or with the help of instruments.
Two kinds of observation
| Qualitative observation | Quantitative observation |
|---|---|
| Describes the quality of something, in words | Describes the quantity of something, with numbers and units |
| Uses the senses only | Needs measuring instruments: ruler, balance, thermometer, stopwatch |
| The mango is yellow and smells sweet. | The mango has a mass of 320 g. |
| The frog's skin feels wet. | The frog is 7 cm long. |
| The plant looks healthy. | The plant is 25 cm tall and has 14 leaves. |
Instruments extend our senses
Our senses have limits. Biologists use instruments to observe what the eye cannot see: a microscope for cells and bacteria, a hand lens for small insects, a stethoscope to hear the heart and a thermometer to measure body temperature.
From observation to a question
A good observation leads to a question. This step is also called recognising the biological problem. A good scientific question:
- can be tested by an experiment or by more observation,
- is clear and specific (it asks about one thing),
- is about the natural world, not about opinions.
| Not a good scientific question | A good scientific question |
|---|---|
| Which flower is the most beautiful? | Do bees visit yellow flowers more often than white flowers? |
| Why are plants nice? | Does a plant grow taller in sunlight than in shade? |
| Is malaria bad? | Do mosquitoes carry the cause of malaria? |
02Real World Examples
At the doctor
A doctor's check-up mixes both kinds of observation: "the throat looks red" (qualitative) and "temperature 38.5 °C, blood pressure 120/80" (quantitative).
Bird watchers at Haleji Lake
Bird watchers at Haleji Lake near Thatta count the migratory birds that arrive from Siberia each winter. Counting year after year shows whether the numbers are going up or down.
Farmers
A farmer who notices that one corner of the field always has weaker crops is making an observation. The next question, "what is different about that corner?", is the start of solving the problem.
03Practice Questions
Try to answer in your own words first, then open the model answer.
Short questions
Q1.What is an observation?Show answer
Answer
An observation is information gathered by using the senses or instruments about something in nature.
Q2.Differentiate between qualitative and quantitative observations. Give one example of each.Show answer
Answer
| Qualitative | Quantitative |
|---|---|
| Described in words | Described with numbers and units |
| Uses the senses | Uses measuring instruments |
| The rose is red. | The rose stem is 30 cm long. |
Q3.Why do biologists prefer quantitative observations?Show answer
Answer
Because they are more accurate and can be checked and compared by other scientists. Words like "big" or "warm" mean different things to different people, but "12 cm" or "37 °C" do not.
Q4.Give three features of a good scientific question.Show answer
Answer
- It can be tested.
- It is clear and specific.
- It is about the natural world, not opinion.
Q5.Classify as qualitative or quantitative: (a) the water is muddy, (b) the pulse rate is 72 beats per minute, (c) the leaf is rough.Show answer
Answer
- (a) qualitative
- (b) quantitative (number and unit)
- (c) qualitative
Long questions
Q6.Explain the role of observation in the scientific method. How are instruments helpful?Show answer
Answer
Observation is the first step of the scientific method. It gives the scientist the facts that lead to a question and then a hypothesis. Careful observation also comes back at the end, when the results of an experiment are observed and recorded.
Our senses are limited and can be fooled, so biologists use instruments:
- a microscope to see cells and microorganisms,
- a balance, ruler and thermometer to measure mass, length and temperature,
- a stethoscope to hear heart and lung sounds.
Instruments make observations more accurate and quantitative.