Investigating biological material at the microscopic level (internal)
Internal 3 credits Microscopy Cell structure Drawing Magnification FunctionAS 91160, 3 credits. Prepare and examine slides of TWO plant tissues and ONE unicellular organism, produce accurate biological drawings, and link structure to function. This standard has only two grades — Achieved and Merit, no Excellence.
1 Reading the notation
Only two grades exist for this standard — and the fixed specimen list is not negotiable.📖 Terms the schedule grades you on
3 terms- Carry out an investigation (Achieved)
- Prepare, view, record as a biological drawing, and relate specialised features to function.
- Investigate in-depth (Merit — the top grade)
- Give reasons for how/why observed features enable the cell to carry out its function. No Excellence exists.
- Biological material
- Two different plant tissues, and one unicellular organism — fixed by the standard.
2 Preparing and drawing to convention
The conventions are assessed directly, independent of how good the observation is.The two calculations
Total magnification eyepiece × objective ×10 and ×40 gives ×400 Actual size drawing size ÷ magnification Convert to µm: 1 mm = 1000 µm ✕The air bubble drawn as a cell
Air bubbles are perfectly circular with a thick, very dark rim and nothing inside. Real cells are irregular, have visible internal structure, and sit in a tissue with neighbours. Drawing a bubble and labelling its parts is a memorable way to lose the observation marks.3 Magnification and actual size
Two formulas, and where the errors usually creep in.Where marks are lost
- No magnification stated on the drawing — the scale is then unknown.
- Mixing mm and µm in the same calculation.
- Forgetting to multiply eyepiece × objective, using only one of the two.
4 Structure, function, and the reason why
Identify → state the function → explain why or how. All three, every time.The three-part link the standard requires
- Identify the feature or organelle observed.
- State its function.
- Give a reason for WHY or HOW it contributes to that function — this is what earns Merit.
Practice
Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.
Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.
Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.
Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.