Bio P3 Line Graph Tips

Tips for Drawing Line Graphs in Biology There are two types of graphs that students often have to draw in Biology exams - the line graph and the bar chart. The line graph is frequently tested, in both the theory paper (Data-based question in Paper 2) and the practical paper. This post focuses on the line graph. The graph question is usually worth about 4 marks because of the 4 areas we look out for: S: Scale P: Plots A: Axes L: Line To add on, it is also important to include a title for your graph and to remember that we are not to extrapolate the line – hence the acronym STAPLE. It may sound like it's only 4 marks and some of you may be tempted to just give that up... but really, it's easy to score the full 4 marks. Follow the tips below, practise drawing all the 10 graphs in the data-based questions in your TYS and these 4 marks will seem like a give-away. I'll elaborate more on the things to look out for based on common mistakes that students make.

Scale The scale you choose should have all plotted points occupying at least 50% of the grid provided, in both the x and y direction. To check for this, just make sure the lowest value and highest value fill at least half of each axis. (See Figure 1 below for illustration of this; purple and maroon font). Be mindful about the scale you use, choose one that is easy to work with. Examples include:  "0, 2, 4, 6...." or  "0, 5, 10, 15...." for each 2cm square on a standard graph paper (or simply put, each "big square"). Also remember not to use "awkward scales". These scales are named as such because the scales cannot be read properly and plotting may become inaccurate. An example would be  "0, 3, 6, 9...." for each "big square". It's difficult to accurately plot a value of 4 in this case. Next, be careful while labelling your scale on each axis. Make sure there are no gaps in the scale. By gaps, I mean this: "0, 5, 10, 20, 25, 30" where 15 is missing from the scale. If the values provided are huge, there is no need to start from zero. To maximise the grid provided, start with a comfortable value just below the provided value or use the actual value if it's suitable for your scale. (See Figure 1 below for example of this). Always remember to label the origin with the starting value of each axis. Many students tend to only label the scale on the axes but would forget the point of origin, especially if it doesn't start with "0". Plots This component is quite easy to score. Just make sure the coordinates are correct when plotting and you'll be fine. If you're nervous or tired, and all the squares seem to merge and... you just can't seem to see exactly which corner of the "small square" your plot should be, use a ruler to guide you so it's harder to make that misalignment mistake. I've written (in bright red) another tip you should follow, in Figure 1 below. Remember to use "x" when marking your plots.

Photo credit: The picture used below is taken from the 2018 GCE O L