Unit 06 · The Frog
The frog is where whole organ systems come into view at once. You make a clean midline incision and pin back the body wall to open the cavity, then read the external landmarks an amphibian carries before locating and naming the heart, lungs, and digestive and urinary organs inside. The work is technique and careful observation: a controlled first cut, looking before you disturb anything, then naming each structure and explaining how the systems work together. An instructor watches you work, and the cavity — opened cleanly, organs intact — is the proof.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Instrument handling & safe technique | Grips the scalpel, scissors, forceps, or probe awkwardly; cuts too hard or too deep; puts hands or specimen at risk. | Holds the instruments correctly with reminders and cuts more carefully, but still presses too hard or steadies the specimen poorly. | Holds each instrument the right way and makes shallow, controlled cuts, working safely for both the student and the specimen. |
| Careful exposure & observation | Cuts before looking and slices through organs while opening the body cavity. | Makes the midline incision roughly and pins the body wall back unevenly, disturbing organs before observing them. | Makes a clean midline incision, pins back the body wall, and opens the cavity without damaging the organs beneath — observing the layout before disturbing anything. |
| Locating & naming external structures | Cannot point to the eyes, tympanum, nares, limbs, or cloaca, or tell fore from hind limb. | Finds a few external landmarks with prompting but confuses the tympanum or misses the nictitating membrane. | Locates and names the eyes and nictitating membrane, tympanum, nares, fore and hind limbs, webbing, and cloaca on the specimen. |
| Locating & naming internal organ systems | Guesses at the organs or names the wrong ones once the cavity is open. | Finds the larger organs but cannot reliably distinguish the small from the large intestine or locate the gallbladder and fat bodies. | Locates and names the heart, lungs, liver, gallbladder, stomach, small and large intestine, kidneys, and fat bodies on the specimen. |
| Explaining structure & function (and specimen care) | Cannot say what a structure does, and lets the specimen dry out or handles it carelessly. | Explains one or two organs' functions but not how the systems connect, and keeps the specimen moist only when reminded. | Explains how key structures do their jobs — the three-chambered heart moving blood, dual respiration through both skin and lungs, the digestive tract from stomach to cloaca — while keeping the specimen moist, handling it respectfully, and cleaning up afterward. |
| 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. |
“This three-chambered heart sits at the front of the cavity — two atria and one ventricle, fewer than ours. Behind it are the two lungs, but a frog also breathes through its skin, so it has dual respiration. I traced the gut from the stomach through the small and large intestine to the cloaca, and the dark bean-shaped organs against the back wall are the kidneys.”
“I cut down the middle but went too deep and nicked something. There’s an organ here — the liver, maybe? I can’t tell the small intestine from the large one.”
You demonstrate this unit by doing the dissection while an instructor watches — opening the body cavity and locating and naming real organ systems on your own specimen while explaining how they work together, not a written test. A criterion counts as mastered only when you can perform the technique cleanly and identify and explain the structures on the actual specimen. 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.