Biological Drawings (Cambridge (CIE) IGCSE Biology): Revision Note

Biological drawing rules

• A biological drawing is a record of what you can actually see, not an artistic impression

• There are specific rules associated with biological drawings; you should always:

  • draw with a sharp pencil, so lines are thin and can be easily corrected

  • draw single, continuous lines, not broken, sketchy or overlapping lines

  • draw smooth outlines that follow the shape of the specimen

  • draw only what is visible

  • avoid shading, cross-hatching or colour

  • use double lines where a structure has two edges, e.g. a vein or a cell wall

• Examiner reports show that students lose marks by:

  • adding shading or texture, so the drawing looks like an artistic impression

  • drawing a broken outline

  • using a ruler to draw part of the specimen, such as the midrib of a leaf

Proportions & use of space

• Your drawing should use most of the space provided, because a small drawing cannot show enough detail

• Plan the size before you start, so that the drawing does not run into the printed text or off the page

• The proportions within the drawing must match the specimen

  • If one part is twice as wide as another in the specimen, it must be twice as wide in your drawing

  • Look carefully at where boundaries between tissues fall before drawing them

• Examiner reports show that students lose marks by:

  • making the drawing so large that it crosses into the text of the question

  • not drawing the exact shape of the tissue layers

Adding labels & label lines

• When labelling a biological drawing you should:

  • draw label lines with a ruler

  • ensure that each label line touches the structure being labelled

  • ensure that label lines do not have arrowheads

  • avoid drawing label lines that cross each other

  • write labels horizontally, outside the drawing, not on top of it

  • use the correct biological terms for the structures

• Examiner reports show that students lose marks by:

  • drawing label lines that stop short of the structure

  • adding arrowheads to label lines

How to calculate the magnification of a drawing

• You may be asked to calculate either:

  • the magnification of your own drawing

  • the actual size of a structure in it

magnification = image size ÷ actual size

actual size = image size ÷ magnification

• Calculate the magnification of a drawing as follows:

  1. Measure the required length on the drawing using a ruler

     • Measure in millimetres unless the question tells you otherwise

  2. Convert both measurements to the same unit

     • Multiply by 1000 to convert millimetres to micrometres

  3. Write down the formula and substitute your values

  4. Use the formula to calculate the magnification

     • Remember that magnification has no unit, so you should write, e.g. ×1500

  5. Check the question to ensure that you have rounded correctly

• Read more about the magnification formula