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 Staining & Contrast unit, a student should be able to:
Five science criteria plus separately reported integration (Page 3).
Stain a slide with iodine or methylene blue and compare fields.
The student explains why the stain and diaphragm reveal detail (Page 4).
Stain used, structures revealed, and the comparison 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 bring the detail out cleanly and justify why the stain and the diaphragm setting reveal it. 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 |
|---|---|---|
| Choosing & applying stain | ||
| Iodine | Lugol's iodine | Stain for plant or starch samples; turns starch blue-black |
| Methylene blue | blue stain | Stain for animal or bacterial cells; darkens nuclei |
| Stain | dye | Adds color to reveal structure; too much buries the detail |
| Contrast & structure | ||
| Draw-through | wicking the stain | Pull stain under the coverslip from one edge — never lift it |
| Over-staining | flooding | Field goes one dark color; dilute or rinse to recover |
| Iris diaphragm | condenser aperture | Closes to build contrast on a stained field; not the brightness knob |
| Stained vs. unstained | comparison field | View both to say what the stain actually revealed |
| Nucleus | cell nucleus | A structure a stain makes visible; nearly invisible unstained |
| Criterion | Developing | Proficient | Mastery |
|---|---|---|---|
| Choosing the stain | Reaches for whatever stain is closest with no reason for the choice. | Knows there are different stains but cannot match one to the specimen. | Chooses iodine for plant or starch samples and methylene blue for animal or bacterial ones, and says why. |
| Applying stain under the coverslip | Lifts the coverslip and floods stain straight onto the specimen. | Places stain at the coverslip edge but does not draw it evenly through. | Adds a drop at one coverslip edge and wicks from the other with paper, drawing the stain evenly under without lifting the coverslip. |
| Avoiding over-staining | Soaks the specimen until the whole field is one dark color. | Uses less stain but still darkens the field past the point of useful detail. | Applies just enough stain to reveal structure, stopping before the field goes muddy, and dilutes or rinses when it does. |
| Tuning the iris diaphragm for contrast | Leaves the diaphragm wide open so a stained specimen washes out. | Adjusts brightness but not the diaphragm to bring out contrast. | Works the iris diaphragm to balance light against the stain so structures stand out without glare. |
| Comparing stained vs. unstained fields | Views only the stained slide and cannot say what the stain changed. | Looks at both but describes them only in vague terms. | Compares a stained field against an unstained one and names the specific structures the stain made visible. |
| 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 control over flooding: too much stain buries the very detail it should reveal. Watch the hands — a drop at one edge, wicked through from the other, and the iris diaphragm tuned for contrast.
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 | Choosing the stain | Dev / Prof / Mast | |
| 2 | Applying stain under the coverslip | Dev / Prof / Mast | |
| 3 | Avoiding over-staining | Dev / Prof / Mast | |
| 4 | Tuning the iris diaphragm for contrast | Dev / Prof / Mast | |
| 5 | Comparing stained vs. unstained fields | 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.