O-Level Biology Quadrat & Transect Biodiversity Walkthrough
Download printable cheat-sheet (CC-BY 4.0)08 Nov 2025, 00:00 Z
Reviewed by
Ezekiel Tan·Academic Advisor (Biology)
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TL;DR
Fieldwork tasks test whether you can sample systematically, record abundance data clearly, and justify ecological conclusions under ACE.
Build muscle memory with random-number quadrat placement, percentage cover estimation, and Simpson’s index so Paper 3 transect questions feel routine.
Stay Plugged Into the Experiment Hub
Cycle this fieldwork routine with the rest of our ecology and enzyme drills at the O-Level Biology Experiments hub so every Paper 3 task type has recent practice.
1 | Syllabus connections
- Section 3 (“Living Together”) in the SEAB syllabus emphasises ecosystem interactions, energy flow, and biodiversity metrics (SEAB 2026 syllabus, PDF).
- Paper 3 fieldwork questions typically assess:
- Planning: choosing random or systematic sampling, justifying quadrat size, accounting for time constraints.
- MMO: placing quadrats accurately, estimating percentage cover, tallying frequency.
- PDO: constructing data tables, computing density/frequency/percentage cover, calculating diversity indices.
- ACE: comparing habitats, explaining biotic/abiotic influences, evaluating sampling limitations.
2 | Random quadrat workflow
| Step | Action | Examiner-friendly note |
| 1 | Lay out two 20 m measuring tapes perpendicular to form a coordinate grid. | Mention the total area covered and justify quadrat size (e.g. 1 m × 1 m). |
| 2 | Use a random number generator to produce x and y coordinates; move the quadrat to each point. | State how many quadrats you will sample (e.g. 10) to ensure adequate coverage. |
