How biology is investigated
An investigable question says what you change, what you measure and what you compare against. “Should forests be protected?” is a good question and is not scientific: it asks for a value judgement. Science says what happens if they are not, and deciding happens elsewhere. The control group answers the question an uncontrolled experiment cannot: would it have happened anyway? It must be identical to the other except in what is being tested. The commonest trap is the confounding variable, something that sneaks in and changes alongside what you study: if the brighter plants sit by the window and you water them in passing, you cannot tell which of the two made them grow. That is why you change one thing only and assign groups at random. And a result that knocks down the hypothesis is a good result.
Where this sits
- Comes after
- The cell
Exercises from this rung
Generated by the app, from easiest to hardest
Which of these can be investigated with an experiment?
- Do more seeds germinate at 20 °C than at 10 °C?
- What is the most important thing in life?
- Is the almond blossom beautiful?
- Should forests over 100 years old be protected?
Why An investigable question names what you change, what you measure and what you compare against. The other three are good questions and are not scientific: two ask for a value judgement and one for a definition. Science does not say what ought to be protected; it says what happens if it is not, and the deciding happens elsewhere.
easierPut an investigation in order.
Answer An observation that puzzles you, A hypothesis that might explain it, A prediction that can be checked, The experiment, with its control, The result, even if it contradicts the hypothesis
Why The step most often skipped is the third: without a concrete prediction, any result seems to fit the hypothesis. And the last defines the trade: a result that knocks down your starting idea is a good result, and publishing it is worth as much as publishing the other kind.
in betweenYou give some plants more light and they grow more. What could spoil the conclusion?
- That the plants were all the same species
- That you measured them with an old ruler
- That the experiment lasted too long
- That you watered them more as well, without noticing
Why A variable that sneaks in and changes alongside the one you are studying: if the brighter plants sit by the window and you water them in passing, you cannot tell which of the two made them grow. It is called a confounding variable, and it is why a serious experiment changes **one thing only** and assigns plants to groups at random.
harder