IAL Biology Edexcel – Core Practical 5 Graticule

Complete Edexcel IAL Biology lesson (spec 3.8, Core practical 5): set up a light microscope, calibrate an eyepiece graticule and measure cells. No prep.

Lesson 11 of 32 · Topic 3 · Unit 2 (WBI12) · Spec 3.8 · 60 minutes
The question this lesson answers: how do I use a light microscope and an eyepiece graticule to measure cells?

By the end, students can

• Make a temporary stained slide of cheek cells safely and focus it from low power to high power.
• Calibrate an eyepiece graticule against a stage micrometer and use the calibration to measure cell size.
• State the main sources of error in the practical and how each is reduced.

How the 15-slide lesson runs
A retrieval starter, then Core practical 5 in two parts. Part one: the aim and big idea, the light microscope and total magnification, and a safe method for a stained cheek-cell slide, with a quick check. Part two: calibrating the eyepiece graticule, then measuring a cell with it, with a second quick check. Both quick checks have answers on the next slide. An exit ticket closes the lesson. The active-learning printables include a paper graticule, so the calibration skill can be practised without a stage micrometer.

Marks students usually lose here

• Re-using a calibration after changing the objective lens, instead of calibrating again for each lens.
• Mixing up eyepiece units and micrometres, or forgetting the conversion factor.
• Describing the method without saying which lens to start with, or that focusing moves away from the slide.

In the folder (13 files)

• PowerPoint, 3-page lesson plan and 20-page student notes with a one-page knowledge organiser
• 5 practice questions (24 marks) and mark scheme, each question on its own page
• 17-mark homework (calibrating with the stage micrometer, an uncalibrated change of lens, plus spaced retrieval) with mark scheme
• 5-question misconception check with teacher key
• 11 pages of active-learning printables: Paper graticule (calibrate, then measure) and Light path (a role play from lamp to eye)
• 8 pages of teacher notes (starter and exit mark points, a step-by-step run sheet for every active-learning activity, answer keys), plus catch-up and extension bank decks

Follows Lesson 10 (microscopes and staining); Lesson 12 covers drawings and exam practice for the same practical. The full 32-lesson Topic 3 bundle is in my shop.

An independent resource by bio_boffin_resources, written by a Biology teacher with 10 years’ experience in a leading international school. Not endorsed by Pearson.