“My notes on diffusion are good, and my notes on active transport are good, but the compare question only gives me half marks.” The notes are fine. The way you build the answer needs to change.
This page belongs to the SPM Biology help pages. For the topic itself, see movement across membranes.
Why does a comparison answer lose marks?
A comparison is marked on points that cover both processes. Two good paragraphs, one per process, leave the marker to do the comparing, and the mark scheme expects you to do it.
The fix is to choose the criteria first. Then each sentence covers one criterion for both processes.
One example: diffusion and active transport
Choose three criteria: direction, energy and carriers. This original table fills them in.
| Criterion | Diffusion | Active transport |
|---|---|---|
| Direction | Down the concentration gradient | Against the concentration gradient |
| Energy | No energy from the cell needed | Energy from respiration needed |
| Carriers | Not always needed | Carrier proteins always needed |
Each row becomes one sentence: “Diffusion moves particles down the concentration gradient, whereas active transport moves them against it.” Both sides appear, and the linking word does the comparing.
For a similarity point, add one sentence: “Both processes move substances across the plasma membrane.”
What can I do on my own?
Use this routine for any pair of processes.
- Write three criteria in a column before you write any sentence.
- Fill each row for both processes.
- Convert each row into a sentence with whereas, but, or both.
- Count the points and compare with the marks.
Try it on a new pair, such as mitosis and meiosis or aerobic and anaerobic respiration. Only the content changes.
When might one-to-one tuition help?
If the points are still thin after this routine, the gap may be in the content, not the format. A one-to-one teacher can ask what differs between the two, then have you write the sentence.
This site gives the method for free, and a teacher gives live feedback on your own writing. See online one-to-one Biology tuition and choosing a useful lesson focus.
What to read next
If the trouble is keeping stages in order, read comparing processes without mixing their stages. The biological data interpretation trainer offers more writing practice.