Biological drawing is marked on rules, not on artistic talent. Nobody is judging whether your cell looks pretty. They are checking a specific list of conventions — so learn the list and the marks are yours.
📚 What you need to know
A biological drawing is a line picture of what you actually saw, not a shaded illustration.
It needs a title and the magnification or a scale bar.
Use a sharp HB pencil on plain white paper. Clear single lines, no shading, no sketchy strokes.
Draw large and in proper proportion.
Label lines must be ruled, must not cross, must have no arrowheads, and must touch the structure exactly.
Keep labels to one side, parallel to the top of the page.
Cell drawings show individual cells at high magnification; plan drawings show tissue outlines at low magnification and never show individual cells.
Draw only what you can see, not what you expect to be there.
The conventions, and why each one exists
Convention
Why it matters
Title and magnification
Without them the drawing has no context and no size information
Sharp pencil, clear single lines
Sketchy overlapping lines make the boundary of a structure ambiguous
No shading
Shading hides detail and adds information you did not measure
Draw large
A big drawing is easier to read and easier to label accurately
Correct proportions
The relative sizes of structures are part of the evidence
Ruled label lines, no arrowheads
An arrowhead covers the very point you are trying to identify
Labels on one side, not crossing
Crossed lines make it impossible to tell which label belongs where
The right-hand drawing contains less ink and more information. That is the whole idea behind biological drawing conventions.
Cell drawings and plan drawings
These are two different tasks and they are marked differently.
A cell drawing is made at high magnification and shows the detail of individual cells and their organelles.
A plan drawing is made at low magnification and shows the outlines of tissues — for example the layers in a leaf cross-section. Individual cells are never drawn in a plan diagram.
If you find yourself drawing dozens of tiny cells in what should be a plan diagram, stop. A plan diagram is a map of the regions, like drawing the outline of countries rather than every house.
Adding a scale bar to your drawing
🧩 Putting a scale bar on a drawing
Calibrate the graticule against the stage micrometer to find what one division is worth.
Swap the micrometer for your specimen and measure it in graticule divisions.
Convert to micrometres by multiplying the number of divisions by the value of each one.
Draw your specimen and measure the length of your drawing in mm.
Make the bar about 20% of that length, and label it with the real distance it represents. If your drawing is 150 mm long, a 30 mm bar labelled with 20% of the real length works well.
Annotation is not the same as labelling. A label names a structure. An annotation names it and says what it does. IB questions often expect annotations, so check the wording — adding a short function to each label is usually the safer choice.
Worked examples
WORKED EXAMPLE
A student’s drawing of a plant cell is shaded, has three crossed label lines with arrowheads, and takes up a quarter of the page. State four ways it could be improved. [4]
Improvement 1
Remove the shading — use clear single lines only.
Improvement 2
Redraw the label lines so they do not cross and are ruled.
Improvement 3
Remove the arrowheads; the line should touch the structure directly.
Improvement 4
Draw much larger, using most of the available space.
Also add a title and the magnification or a scale barfor a 4-mark question, give four separate, specific improvements
WORKED EXAMPLE
A drawing of a specimen is 150 mm long. The specimen is really 300 µm long. Calculate the magnification, and state how long a scale bar representing 20% of the specimen should be.
Step 1: convert units150 mm × 1000 = 150 000 µmStep 2: magnification150 000 ÷ 300 = 500Step 3: the scale bar20% of 300 µm = 60 µm; 20% of 150 mm = 30 mm× 500; draw a 30 mm bar labelled 60 µmthe bar length and its label are two different numbers – keep them straight
💡 Exam tip
Before you hand it in, check for the four easy marks: title, magnification or scale bar, no shading, ruled labels.
Use a ruler for label lines. Freehand lines look sketchy and can lose the mark.
Draw big. There is almost no such thing as too large in a biological drawing.
Keep all label lines parallel to the top of the page and on one side where you can.
Add the function of each structure if the question asks you to annotate.
For plan diagrams, draw tissue outlines only — never individual cells.
⚠ Common mix-up
Shading to show colour or depth. Biological drawings are line drawings only.
Putting arrowheads on label lines. The line should simply touch the structure.
Drawing what you expect rather than what you see. If you cannot see a mitochondrion, do not draw one.
Drawing individual cells in a plan diagram. That is the single most penalised mistake here.
Leaving out the title or magnification. Two of the easiest marks in the whole paper.
Confusing the scale bar’s drawn length with its label. One is on the page, the other is the real distance.
Up next: Cell Membranes — a closer look at the phospholipid bilayer, the proteins in it, and how substances actually get across.
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