This is a working draft for Leslie's review. The dependency edges below are a first pass — the diagram and the prerequisite table are the parts to check hardest, since they drive hold-vs-advance decisions.
The course map shows the eight units as a spine — the microscope first, micrography last. But the real prerequisite structure isn't a straight line: it's a directed graph. Microscopy skills are more strictly cumulative than most subjects — measurement needs the scope, wet mounts need steady measurement, and plant and animal work need both mounting and staining. A weak skill early doesn't just lower one grade, it cascades into everything downstream that needs it. This page is the map a guide uses to find the skill that's actually blocking a stuck student.
An arrow means “must be mastered first.” Units 05, 06, and 08 each pull from two upstream units — those are the cascade points where one soft prerequisite quietly breaks several later units.
Prerequisite gating
A unit unlocks when its prerequisites are mastered — demonstrated, not merely seen. "Covered in class" is not the gate; a cleared rubric is. The difference matters most at the cascade points, where a soft prerequisite quietly breaks two or three later units.
| Unit | Must have mastered first |
|---|---|
| 01 The Microscope | — (entry point) |
| 02 Magnification & Measurement | 01 (you must know the scope and its optics before measuring through it) |
| 03 Preparing Wet Mounts | 02 (clean mounts depend on knowing magnification and focus) |
| 04 Staining & Contrast | 02 (staining choices depend on what you can resolve) |
| 05 Plant Cells & Tissues | 03 (wet-mount technique) + 04 (staining for contrast) |
| 06 Animal Cells & Histology | 03 (wet mounts) + 05 (reading cells before tissues) |
| 07 Microorganisms | 05 (finding and reading small cells first) |
| 08 Micrography | 06 (histology-level detail) + 07 (microbe identification) |
Gap-cascade diagnosis
When a student stalls late, the visible symptom is rarely the real problem — the broken skill is usually upstream. Trace the arrows backward. Common cascades:
| Late symptom | Upstream concept to check first |
|---|---|
| Scale bars and micrographs come out wrong (Unit 08) | Measurement from Unit 02 — a scale bar is only as trustworthy as the eyepiece-scale calibration behind it. |
| Structures won't resolve in a stained slide (Unit 06) | Staining technique from Unit 04 — poor contrast, not poor observation, is usually the culprit. |
| A microbe hunt finds nothing (Unit 07) | Wet-mount technique from Unit 03 — a bad mount hides the specimen before identification even starts. |
| Plant sections come up blank or torn (Unit 05) | Wet-mount & sectioning technique from Unit 03 — the specimen was lost at preparation. |
Using the graph to plan a re-attempt
The graph turns a "not yet" into a targeted re-attempt instead of a whole-unit re-teach. When a student fails a downstream demonstration:
- Trace backward to the upstream node the symptom points to.
- Re-attempt the upstream skill first — close the gap at its source, not where it surfaced.
- Then re-run the downstream demonstration. Often it passes without any re-teaching of the downstream unit at all, because the cascade is resolved.
This is also where the integration guide matters: some microscopy skills depend on an applied-math idea — ratios for magnification, proportional reasoning for scale bars — from another spoke. When the upstream microscopy node looks solid but the student still stalls, check the cross-disciplinary dependency before re-teaching the microscopy.