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 — what makes something alive first, human impact on living systems last. But the real order isn't a straight line: it's a web of “you need this before that.” Life science builds on itself — you can't understand body systems until you understand cells, and evolution only makes sense once you know how traits pass from parents to offspring. A shaky idea early doesn't just cost one grade, it cascades into everything downstream that leans on it. This page is the map a guide uses to find the idea 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 Characteristics & Needs of Living Things | — (entry point) |
| 02 Cells & Their Structures | 01 (you sort living from non-living before you look inside a living thing) |
| 03 From Cells to Organisms | 02 (tissues, organs, and organ systems are built from cells) |
| 04 Genetics & Heredity | 02 (genes live inside the cell’s nucleus) |
| 05 Evolution & Adaptation | 03 (whole organisms & their traits) + 04 (traits pass through genes) |
| 06 Classification & the Kingdoms of Life | 03 (you sort whole organisms by observable traits) + 05 (shared traits reflect common ancestry) |
| 07 Ecosystems & Interdependence | 05 (organisms & the adaptations that fit them to their environment) |
| 08 Human Impact on Living Systems | 06 (identifying species — native vs. invasive) + 07 (how the parts of an ecosystem connect) |
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 |
|---|---|
| Human-impact reasoning falls apart (Unit 08) | Ecosystems from Unit 07 — you can't weigh an impact until you see how the living and non-living parts connect. |
| Classifying organisms breaks down (Unit 06) | Whole-organism structure from Unit 03 — you sort by observable traits, and those traits are body features. |
| Ecosystem roles don't make sense (Unit 07) | Adaptation from Unit 05 — an organism's role depends on the traits that fit it to its environment. |
| Natural-selection reasoning goes wrong (Unit 05) | Where the traits come from — genes and heredity, Unit 04. |
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 life science ideas lean on a skill from another spoke — careful measurement and scale for the microscope, close reading and note-taking for the lab notebook. When the upstream life science node looks solid but the student still stalls, check the cross-disciplinary dependency before re-teaching the life science.