IAL Biology Edexcel – Microscopes and Staining

Complete Edexcel IAL Biology lesson (spec 3.7): light v TEM v SEM, why electrons resolve more, and staining, with three real WBI12 questions.

Lesson 10 of 32 · Topic 3 · Unit 2 (WBI12) · Spec 3.7 · 59 minutes
The question this lesson answers: how do light and electron microscopes differ, and why do we stain specimens?

By the end, students can

• Compare light, transmission electron and scanning electron microscopes for resolution, wavelength, specimen and image.
• Explain why electrons give higher resolution than light, and why specimens are stained.
• Write comparisons that name both microscopes, as the mark scheme demands.

How the 23-slide lesson runs
A retrieval starter, then light and electron microscopes compared, resolution (why electrons show more detail), and TEM v SEM (through a slice or over the surface), with a quick check. Staining follows: making structures stand out, and “stains and false colour: which does what?”, with a second quick check on choosing a microscope. Three real WBI12 questions have official mark schemes and model answers: June 2021 Q2, part a(i) and (ii); October 2019 Q3, part b(i) and (ii); and January 2022 Q2, part a. An exit ticket closes the lesson.

Marks students usually lose here

• Writing “the electron microscope has a higher magnification” without saying resolution.
• Answering about only one microscope in a “compare” question.
• Saying stains and false colour do the same thing: stains are added to a specimen, false colour is added to the image afterwards.

In the folder (13 files)

• PowerPoint, 3-page lesson plan and 14-page student notes with a one-page knowledge organiser
• 8 practice questions (35 marks) and mark scheme, each question on its own page
• 18-mark homework (methylene blue on cheek cells, choosing the right microscope for three specimens, plus spaced retrieval) with mark scheme
• 5-question misconception check with teacher key
• 4 pages of active-learning printables: The dot test (when do two dots become one?)
• 6 pages of teacher notes (starter and exit mark points, a step-by-step run sheet for the active-learning activity, answer keys), plus catch-up and extension bank decks

Follows Lesson 9 (magnification and units); Lesson 11 is the core practical on drawing and measuring cells. 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.