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 definition of an animal first, behavior and ecology last. But the real prerequisite structure isn't a straight line: it's a directed graph. Zoology is cumulative — the invertebrate phyla build on the simplest animals, vertebrates build on invertebrate body plans, and behavior and ecology draw on the whole animal range. A weak concept 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 concept 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 What Is an Animal? | — (entry point) |
| 02 Sponges, Cnidarians & Worms | 01 (the definition of an animal & basic body organization come first) |
| 03 Mollusks & Arthropods | 02 (tissues, symmetry & the first body cavities of the simplest animals) |
| 04 Echinoderms & the Chordate Transition | 02 (deuterostome body plans build on the earliest animal tissues) |
| 05 Fish & Amphibians | 03 (invertebrate body plans) + 04 (the chordate transition that precedes vertebrates) |
| 06 Reptiles & Birds | 03 (arthropod prey & the invertebrate food base) + 05 (vertebrate anatomy — amniotes build on fish & amphibians) |
| 07 Mammals | 05 (vertebrate anatomy — the mammalian plan is modified vertebrate anatomy) |
| 08 Animal Behavior & Ecology | 06 (reptile & bird behavior) + 07 (mammalian behavior — ecology draws on the whole range) |
Gap-cascade diagnosis
When a student stalls late, the visible symptom is rarely the real problem — the broken concept is usually upstream. Trace the arrows backward. Common cascades:
| Late symptom | Upstream concept to check first |
|---|---|
| Behavior-and-ecology arguments stay vague (Unit 08) | Mammals from Unit 07 — you can't reason about social systems and adaptation without the mammalian range they draw on. |
| Mammal anatomy reasoning collapses (Unit 07) | Fish & amphibian vertebrate anatomy from Unit 05 — the mammalian plan is modified vertebrate anatomy. |
| Reptile & bird adaptations don't make sense (Unit 06) | Fish & amphibian anatomy from Unit 05 — amniote body plans are modified vertebrate anatomy. |
| Fish & amphibian anatomy confuses the student (Unit 05) | Invertebrate body plans from Units 03–04 — structure-function reasoning starts with the simpler phyla and the chordate transition. |
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 concept 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 zoology concepts lean on a reading or observation skill from another spoke — keying out a specimen with a dichotomous key, reading a distribution map — not on an upstream zoology unit. When the upstream zoology node looks solid but the student still stalls, check the cross-disciplinary dependency before re-teaching the zoology.