“I have never seen this graph before, so I do not know what to write.” The graph may be new, but the way to read it is the same each time.
This page belongs to the SPM Biology help pages. The example uses an idea from leaves and photosynthesis.
Why does a new graph cause a freeze?
Some students wait to recognise the graph before they start. But a short routine works on any graph, whether or not you have seen it before.
Start with the routine. Once you are doing the steps, the reading follows.
One example: five steps on an invented data set
An original experiment measured the rate of oxygen bubbles from a water plant at different light intensities. The values are invented.
| Light intensity (arbitrary units) | 0 | 2 | 4 | 6 | 8 | 10 |
|---|---|---|---|---|---|---|
| Bubbles per minute | 0 | 8 | 16 | 24 | 28 | 28 |
Apply the five steps:
- Axes: light intensity on the x-axis, bubbles per minute on the y-axis.
- Overall trend: the rate rises, then levels off.
- Figures: from 0 to 6 units the rate rises from 0 to 24 bubbles per minute, or 4 bubbles for each unit.
- Change: from 8 to 10 units the rate stays at 28 bubbles per minute.
- Reason: after 8 units, light is no longer the limiting factor. Another factor, such as carbon dioxide concentration or temperature, limits the rate.
What can I do on my own?
Use this sentence frame for every graph: “As X increases from __ to __, Y increases from __ to __. After __, Y stays at __, because __.”
Practise with graphs from SPM-style questions. Do steps 1 to 4 first without thinking about the biology, then add the reason. Keeping description and reason apart makes each easier.
When might one-to-one tuition help?
If you can describe the trend but cannot find the reason, the gap is in the topic itself. A one-to-one teacher can give you three unfamiliar graphs in a row and ask you to explain each one aloud.
The free graph tools let you practise the routine, and a teacher gives live feedback on your reasons. See online one-to-one Biology tuition for how starting works.
What to read next
For experiment tables, read reading unfamiliar Biology experiment data. The graph evidence and fair-comparison lab offers more graphs to read.