Unit 02 · Roots, Stems & Leaves
Anatomy is where the plant becomes a working body. This unit follows the two great systems — the root system that anchors and absorbs and the shoot system that lifts leaves to the light — through primary growth at the tips and the secondary growth that thickens woody stems. You read leaf anatomy from the epidermis and its stomata down through the photosynthetic mesophyll and the veins, and trace how xylem and phloem are arranged differently in roots and stems. Mastery means you can look at a real cross-section and explain each layer as a structure doing a job, not a diagram to label.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Root & shoot systems | Cannot say what roots and shoots each do for the plant. | Names the two systems but confuses their organs or jobs. | Distinguishes the root and shoot systems, names the organs of each, and explains how anchorage, absorption, support, and light capture divide between them. |
| Primary vs. secondary growth | Thinks all growth is just getting taller. | Defines primary growth but cannot explain what makes a stem woody. | Separates primary growth at the apical meristems from secondary growth at the vascular cambium, and explains how the cambium adds girth and wood. |
| Leaf anatomy | Sees a leaf as a flat green sheet with no internal structure. | Names epidermis and veins but not the mesophyll layers or the role of stomata. | Identifies epidermis, palisade and spongy mesophyll, stomata, and veins in a leaf section, and explains how each supports photosynthesis and gas exchange. |
| Xylem & phloem organization | Cannot tell xylem from phloem or say what each carries. | Knows xylem carries water and phloem carries sugar but not how they are arranged. | Locates xylem and phloem in a stem and a root, explains the different arrangements, and relates modified organs like bulbs or tubers back to their tissues. |
| Lab technique (dissection & microscopy of plant sections) | Cannot cut a clean section or bring it into focus. | Makes a section but misidentifies mesophyll, cambium, or the vascular bundles. | Cuts a thin stem, root, or leaf section, focuses it under the scope, and correctly identifies the tissue layers and vascular arrangement. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“You can see it in the stem cross-section — the xylem sits toward the inside and the phloem toward the outside, with the cambium ring between them adding girth each year. In the leaf, the tall palisade cells near the top are packed with chloroplasts for light, and the stomata on the underside open to let CO₂ in.”
“Roots are the bottom part and leaves are green. There’s tubes inside — one is xylem, I think. I found the section but I’m not sure which layer is which.”
You demonstrate this unit through dissection and microscopy labs — sectioning roots, stems, and leaves and reading them under the scope — plus short oral checks where you reason from what you see aloud, not a multiple-choice test. A criterion counts as mastered only when you can both run the technique and justify the plant biology behind it. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.