scholarlab.KS5 Biology

COMMAND WORD · BIOLOGY

Plot

Mark the data accurately on a scaled grid, and add a line of best fit only when the pattern supports one.

All command words

Method

Axes and an even scale, then every point, then a line only if it fits.

What the parts mean

  • Axesthe quantity, the unit and an even scale, with the independent variable on x
  • Pointsevery coordinate you were given
  • Linea best fit only when that shape is honest

How to build your answer

  1. 1Label both axes with units and choose an even scale that uses the grid.
  2. 2Plot every point, including one you might later question.
  3. 3Draw a straight best-fit line only if the points support it. Use a curve if they do not.

Biology exemplar

Original question

Plot these illustrative points and say what line is appropriate: (10 °C, 1), (20 °C, 2), (30 °C, 3), (40 °C, 2.5), with rate in arbitrary units.

Four points: rate 1 at 10 °C, 2 at 20 °C, 3 at 30 °C and 2.5 at 40 °C. No line is drawn.0102030405001234Temperature / °CRate / arbitrary units
Rate in arbitrary units. No line has been added. That choice is part of the command.

Annotated answer

AxesTemperature / °C on x and rate / arbitrary units on y, with even scales. PointsAll four points are marked. LineOne straight line across the whole range does not fit, because the rate rises and then falls.

The labels match the frame. Read them in order. This is one accurate route, not the only one.

Exam habit

Check that you can read a value back off your scale.

Common pitfall

Forcing a straight line through a rise and a fall, or through the origin when the points do not go there.

Exam-style question

3 marks

Based on a sample question

Mark points shown after marking

The table shows the mean heart rate of water fleas at four caffeine concentrations.

Caffeine / mmol dm⁻³Mean heart rate / bpm01480.516211812179
Illustrative data.

Plot a suitable graph of these results on the pad.

(3)

Graph skills: SLAPUK and choosing a scale

Draw your answer in the box below. Then press Show model answer and tick each point your drawing shows.

Draw here

Draw with a mouse, finger or stylus.

Total for this question: 3 marks

Answer discussion

Caffeine goes on the x-axis and mean heart rate, with the unit bpm, on the y-axis. The points rise and then the 2.0 mmol dm⁻³ point is slightly lower, so one straight line through all four hides that. A sentence about the trend, with no graph, is a description.

Where this comes from

Unit 6 sample paper. Question 2 (b) asks you to plot caffeine concentration against the mean heart rate of Daphnia. Sample assessment, not a live paper.

Sample paper WBI16/01, question 2 (b) (3 marks), 2017 sample assessment. Question page · Mark scheme page

Sources

Pearson Biology specification · Sample assessment PDF