Use these targets, vocabulary, rubrics, examples, and score sheet with the instructor's approved lesson and procedure. This is an assessment companion, not a complete lesson or safety authorization.
By the end of the Plant Cells & Tissues unit, a student should be able to:
Five science criteria plus separately reported integration (Page 3).
Mount onion and elodea; locate each structure on the scope.
The student names each structure on sight (Page 4).
Specimen, structures found, and a labeled sketch kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Developing, Proficient, or Mastery — the column language tells you which. A criterion counts as mastered only when the student can both prepare the mount and name what they see without guessing. Each student has three tokens per term; each token retries one rubric criterion. Approved accommodations, equipment failures, and approved absences are handled separately and do not consume these tokens.
Accept listed synonyms; use the distinction column to resolve near-matches.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Preparing the mount | ||
| Wet mount | living mount | Specimen under a coverslip in water or stain — keeps cells alive to view |
| Coverslip | cover glass | Lower it from an angle so no air bubbles are trapped |
| Iodine stain | potassium-iodide stain | Darkens the nucleus and starch so structure shows in onion |
| Epidermis peel | onion-skin layer | A single cell layer thin enough for light to pass through |
| What you locate | ||
| Cell wall | rigid outer wall | The boxy plant-cell boundary; animal cells have none |
| Nucleus | cell control center | The dark central body iodine makes stand out |
| Chloroplast | green plastid | Green body in elodea; absent in onion — site of photosynthesis |
| Guard cells & stoma | stomatal pore | Paired cells around a leaf pore that opens and closes |
| Criterion | Developing | Proficient | Mastery |
|---|---|---|---|
| Preparing plant wet mounts | Floods the slide or traps bubbles under the coverslip so nothing is clearly in view. | Mounts onion or elodea but tears the epidermis or drops the coverslip so air bubbles crowd the field. | Peels a thin onion epidermis or an elodea leaf, adds iodine or water, and lowers the coverslip to give a clean, bubble-free wet mount. |
| Locating cell structures | Cannot point to the cell wall, nucleus, or vacuole, or expects chloroplasts in onion where there are none. | Finds the cell wall but hunts for the nucleus, or misses that elodea's green bodies are chloroplasts. | Locates cell wall, nucleus, and vacuole in onion and adds chloroplasts and cytoplasmic streaming in elodea — naming each on sight. |
| Finding guard cells & stomata | Does not know what a stoma looks like and scans past the guard cells. | Finds a stoma when shown one but cannot relocate the pattern on a fresh field. | Locates paired guard cells and the stomatal pore on a leaf peel and explains what the opening does. |
| Distinguishing tissue regions | Treats the whole mount as one uniform sheet of identical cells. | Notices cells differ but cannot say which region is which. | Tells epidermis from the cells beneath it and reads how a tissue region's cell shape fits its job. |
| Resolving structure at the scope | Settles for a blurry blob and guesses at what it “should” be. | Gets a partial focus but cannot bring a whole structure into crisp view. | Works the fine focus and diaphragm until walls and organelles resolve sharply, and reports only what is actually in view. |
| Integration (cross-domain) | Makes no supported connection between the source and the science. | Uses the source but needs help connecting evidence, writing, or limitations to the science. | Independently connects History, Reading, and Writing using a cited source, appropriate evidence, a limitation, and a scientific explanation. |
The split between Proficient and Mastery is the image, not the guess: a mastered student brings the structure into sharp focus and names it on sight. Ask “focus that up and show me the nucleus.”
Read these before you grade. They show what Mastery and Developing actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Preparing plant wet mounts | Dev / Prof / Mast | |
| 2 | Locating cell structures | Dev / Prof / Mast | |
| 3 | Finding guard cells & stomata | Dev / Prof / Mast | |
| 4 | Distinguishing tissue regions | Dev / Prof / Mast | |
| 5 | Resolving structure at the scope | Dev / Prof / Mast | |
| 6 | Integration (cross-domain) | Dev / Prof / Mast |
☐ No ☐ Yes — for criterion: __________
Tokens left this term after this session (choose one): ☐ 3 ☐ 2 ☐ 1 ☐ None left
Dev = Developing · Prof = Proficient · Mast = Mastery · Unsure between two levels? Circle the lower one and note what a re-do would need.