A blank nine-step write-up with the correct table headings. Print it for a real lesson and fill it in by hand. See the specimen lab book
Blank write-up: Microscopy
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Study Hack Lab
RP 1 · Biology
Microscopy
Write-up template
Name
Date
Course
GCSE Biology
Board and specification
AQA GCSE Biology (8461), 4.1.1.2AQA GCSE Combined Science: Trilogy (8464), 4.1.1.2Apparatus and techniques: AT 1, AT 7
Class and teacher
Aim
Use a light microscope to observe, draw and label onion cells and cheek cells, measure onion cells with a calibrated eyepiece graticule, and work out the magnification of your drawing.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
A light microscope magnifies twice: the objective (×4, ×10 or ×40) and the eyepiece (×10), so the total is ×40, ×100 or ×400. The eyepiece scale has no units of its own, so it is calibrated against a stage micrometer for each objective. Light passes up through the specimen, so it must be thin; a stain makes the colourless parts show.
magnification = size of image ÷ size of real object
Variables
Independent (you change)
Dependent (you measure)
Control (you keep the same)
Prediction
Which of these will you be able to see in onion cells at ×400 with a light microscope?
You turn from the ×10 to the ×40 objective. What happens to what you see?
How will your onion cells compare in size with your cheek cells?
Risk assessment
Hazard
Harm it could cause
Control
2 Apparatus
Light microscope (eyepiece ×10; objectives ×4, ×10 and ×40) with a lamp Magnifies the cells ×40, ×100 or ×400.
Eyepiece graticule (a 100-division scale in the eyepiece) (resolution 1 division) A scale seen on top of the cells, to measure them.
Stage micrometer slide (1 mm in 100 divisions) (resolution 0.01 mm) A known length to calibrate the graticule.
Microscope slides and coverslips Hold the specimen flat under the microscope.
Onion, white tile and scalpel The plant tissue, and a safe surface to cut on.
Forceps and a mounted needle Peel and flatten the tissue; lower the coverslip.
Dropping pipette and water One drop of water to mount the tissue in.
Iodine solution in a dropper bottle Stains the nucleus and cytoplasm yellow-brown.
Filter paper Soaks up extra liquid from round the coverslip.
Sterile cotton buds, methylene blue and a beaker of disinfectant Cheek cells: collect, stain, then dispose of the buds safely.
Prepared slide of cheek cells Animal cells, if your school does not take cheek cell samples.
Safety goggles Protect your eyes from iodine solution.
Sharp pencil, ruler and plain paper For the labelled drawing.
3 Method
Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.
4 Results
The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.
Observations
Looking at
What you saw
Onion slide, ×40
Air bubbles, ×100
Onion cells, ×400
Cheek cells, ×400
Calibrating the eyepiece graticule · The stage micrometer is 1 mm long, in 100 divisions of 0.01 mm (10 µm).
Calibration
Value
Eyepiece divisions equal to 0.50 mm (×10)
Length of one eyepiece division in µm
Lengths of onion epidermis cells (×10 objective) · Each cell measured along its length, from one end wall to the other.
Cell number
Length of cell in eyepiece divisions
Length of cell in µm
1
2
3
4
5
Mean
Estimate from the field of view (×100)
Field of view
Value
Diameter of the field of view in µm
Cells end to end across it
Estimated length of one cell in µm
Anomalies
Ring any anomalous result. Say what probably went wrong and whether you repeated it.
5 Graph
This practical has no graph: summarise your results in a sentence.
6 Analysis
One eyepiece division
length of one division = length on the stage micrometer ÷ number of eyepiece divisions
Answer
Lengths in µm
Answer
Mean length
mean = sum of the lengths ÷ number of lengths
Answer
Estimate from the field of view
length of one cell ≈ diameter of the field of view ÷ number of cells across it
Answer
Draw and label
Answer
Magnification of your drawing
magnification = size of image ÷ size of real object
Answer
7 Conclusion and evaluation
Conclusion
Conclusion: what do your results show? Use your own numbers.
Sources of error
For each, say whether it is systematic or random, and how it affected your results.
Graticule not calibrated, or calibrated with a different objective
Measuring across the cell at an angle instead of along its length
Thick or overlapping tissue
Lining up the cell walls with the scale (resolution: one division, about 10 µm at ×10)
Cells differ in size (biological variation)
A torn cell or an air bubble measured as if it were one cell
Improvement
How could you improve the method? Say why it would help.
8 Make safe and clear up
Turn back to the ×4 objective and lower the stage
Switch off the lamp, unplug it and put the cover on the microscope
Put used slides and coverslips in the glass waste, and cotton buds in the disinfectant
Wipe up any iodine, wash the tile and scalpel, then wash your hands