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Learn it your way
A short class with Sarah and her students. The other ways are under More.
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We can take photographs through a microscope. So why do biologists still make drawings?
Drawing makes you look more carefully at the specimen.
Yes, and a drawing can show clearly what matters. But it must show what you actually see. Should you draw mitochondria in an onion cell at ×400?
Only if we can really see them, and usually we can't.
Exactly. Draw what you see, not what you know from the textbook.
So if the cell membrane is pressed against the cell wall and I can't see it separately, I don't draw a separate line?
Right. Honesty is the first rule of scientific drawing.
What should you draw with?
A sharp pencil, so we can rub out mistakes.
And should you shade the nucleus to show it is darker?
No shading or colouring, just clear outlines.
Good. Now the label lines. How should they look?
Drawn with a ruler, touching the structure, with no arrowheads, and never crossing each other.
Perfect, with the labels written outside the drawing and lined up neatly.
Here is a label: 'nucleus'. How could we turn it into an annotation?
Nucleus: stained darker by iodine, and it controls the cell's activities.
Excellent. An annotation adds what you observed or what the structure does. What does the title need?
What the specimen is, the stain, and the magnification, like 'onion epidermis, iodine, ×400'.
Good. And how would a cheek cell drawing differ from the onion one?
No cell wall and no large vacuole, and its shape is irregular.
Exactly. Your annotations should point out those differences.
Record only the structures actually visible in your specimen.
Use a sharp pencil, continuous lines, no shading, and a large drawing in proportion.
Ruled, touching the structure, without arrowheads, never crossing, with labels outside the drawing.
A label names a structure; an annotation adds an observation or a function.
State the specimen, the preparation (such as the stain) and the magnification.
An onion epidermis drawing at ×400 shows a few brick-shaped cells with labels for the cell wall, cytoplasm, nucleus and vacuole, and an annotation noting that the nucleus is stained darker by iodine.
A cheek cell drawing at ×400 shows an irregular cell with a thin membrane and a dark blue nucleus, with an annotation noting that there is no cell wall.
A low-power plan diagram of a leaf section shows the outlines of the upper epidermis, palisade layer, spongy layer and lower epidermis, without drawing any individual cells.
Sharp pencil, no shading, lines clean and neat; ruled labels outside, where they never meet.
A detective sketches a crime scene for the court. She draws only what is really there, in clear pencil lines, labels each item with a ruled line, adds notes on why each clue matters, and writes the date and place at the top.
See it, Sketch it, Spell it out: draw what you see, draw it cleanly, then label and annotate.
L.A.T. - Labels, Annotations, Title: the three things every drawing needs besides the drawing itself.
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What should biological drawings be drawn with?
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Label or annotation?
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Rules for label lines
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What goes in the title of a drawing?
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Plan diagram
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An accurate pencil drawing that records what is seen in a specimen.
A word or phrase naming a structure on a drawing.
A short note on a drawing that describes an observed feature or the function of a structure.
A ruled line, without an arrowhead, joining a label to the structure it names.
A low-power drawing that shows the outlines of tissues without individual cells.
A dye, such as iodine or methylene blue, that makes structures easier to see.
How many times larger an image is than the real object; for a microscope, eyepiece times objective.
An annotated biological diagram is a clear pencil drawing of what you actually see, with ruled label lines naming each structure and short notes (annotations) explaining its features or function, plus a title that states the specimen, stain and magnification.
This lesson teaches the conventions scientists use to record observations as biological drawings. It explains why we draw what we see rather than what a textbook shows, sets out the rules for lines, size, labels, label lines and titles, and shows the difference between a label and an annotation. Worked examples annotate an onion epidermis cell and a human cheek cell, compare a low-power plan diagram with a high-power drawing, and list the most common mistakes to avoid.
A biological drawing is a record of an observation. It forces you to look carefully, and it shows other people exactly what you saw. A good drawing is accurate and clear rather than artistic, and it follows a set of conventions that every biologist recognises.
Draw the specimen in front of you, not the ideal cell from a textbook. If a structure is not visible, leave it out. For example, in an onion epidermis cell at ×400, the cell membrane is pressed tightly against the cell wall and cannot be seen as a separate line, and mitochondria are too small to see clearly, so neither should be drawn as if it were. Draw a few representative cells carefully, not the whole field of view.
A label simply names a structure: "nucleus". An annotation adds a short note about a feature you observed or the structure's function: "nucleus: stained darker by iodine; controls the cell's activities". Annotations turn a drawing into an explanation.
Every drawing needs a title that says what the specimen is, how it was prepared and how it was viewed, for example: Onion epidermis cells, stained with iodine, viewed at ×400. The magnification of the microscope is the eyepiece magnification multiplied by the objective magnification (×10 × ×40 = ×400). Working out the magnification of the drawing itself is covered in the next lesson.
At low power, a plan diagram shows the outlines of tissues, such as the layers in a leaf section, without drawing individual cells. At high power, a detailed drawing shows a few individual cells and the structures inside them. Use the type that fits your purpose.
Drawing in pen; shading; sketchy lines; arrowheads on label lines; label lines that cross; labels written inside the drawing; a tiny drawing; drawing structures that were not seen; and a missing title or magnification.