IAL Biology Edexcel – Root-Tip Squash Practical

Complete Edexcel IAL Biology lesson (spec 3.15–3.16, Core practical 6): the root-tip squash in six steps, naming the stages, and the mitotic index.

Lesson 22 of 32 · Topic 3 · Unit 2 (WBI12) · Spec 3.15–3.16 · 61 minutes
The question this lesson answers: how do I prepare a root-tip squash, and how do I start to calculate a mitotic index?

By the end, students can

• Describe the six steps of the root-tip squash and justify each one, including the safety precautions.
• Recognise the stages of mitosis in a stained squash, using clues and avoiding the traps.
• Define the mitotic index and calculate it from a count of cells.

How the 23-slide lesson runs
A retrieval starter, then where to look (the root-tip meristem), the core practical in six steps, and “justify every step” with the reason in mark-scheme words. Safety and repeatability, making the squash and finding the cells, and recognising the stages follow, then “clues and traps when naming a stage” and a quick check. Two real practical-paper questions (WBI13 June 2022 Q2, part a, and a June 2026 question) have official mark schemes and model answers. The lesson closes with “what is the mitotic index?” and an exit ticket. The active-learning pack includes a “Stage detectives” activity for practising how to name each stage.

Marks students usually lose here

• Giving the step but not the reason, for example “warm hydrochloric acid” without “breaks the middle lamella so cells separate”.
• Looking for mitosis in the wrong part of the root, rather than the meristem just behind the tip.
• Counting cells in mitosis only, or leaving interphase out of the total.

In the folder (13 files)

• PowerPoint, 3-page lesson plan and 20-page student notes with a one-page knowledge organiser
• 8 practice questions (26 marks) and mark scheme, each question on its own page
• 18-mark homework (why acid and acetic orcein, a safety precaution, overlapping cells, naming four cells, plus spaced retrieval on DNA replication) with mark scheme
• 5-question misconception check with teacher key
• 15 pages of active-learning printables: Order the squash, Safety strip, and Stage detectives
• 11 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 21 (the spindle and identical cells); Lesson 23 is mitotic-index calculations and cancer data. 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.