Unit 05 · Fish & Sharks
Fish are the vertebrates that never left the water. This unit covers how they’re built — fins, gills, the lateral line, and the swim bladder — and splits them into the two great groups: cartilaginous fish like sharks and rays, and the bony teleosts. You learn how buoyancy and gas exchange work, from the swim bladder that most bony fish adjust to the counter-current gills that pull oxygen from water, and why a shark, lacking a swim bladder, must keep water moving. Along the way you correct the biggest myth in the unit — most sharks are no threat to people. Mastery means you can read a fish’s body as a set of answers to living underwater.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Fish anatomy | Cannot name a fish’s main external features. | Labels fins and gills but misses the lateral line or swim bladder. | Identifies fins, gills, the lateral line, and the swim bladder and says what each one does. |
| Cartilaginous vs bony fish | Treats all fish as one kind. | Knows sharks differ but cannot say the skeleton is the reason. | Distinguishes cartilaginous fish (sharks and rays) from bony teleosts by skeleton and other traits. |
| Buoyancy & gas exchange | Thinks fish breathe air or float without effort. | Names the swim bladder or gills but not how they work. | Explains swim-bladder buoyancy and counter-current gill exchange, and why sharks without a swim bladder must swim or pump water. |
| Adaptations & shark biology | Describes sharks only as dangerous predators. | Names a feeding or movement adaptation but repeats the “man-eater” myth. | Explains adaptations for feeding and movement and states plainly that most sharks pose no danger to people. |
| Lab technique (fish anatomy & adaptation study) | Handles the specimen carelessly or skips the structures. | Examines the fish but cannot link structure to function. | Runs a clean fish anatomy study — locates each structure and explains the adaptation it represents, recorded accurately. |
| 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. |
“It’s a bony fish — it’s got a swim bladder to hold its depth without swimming, and its gills run counter-current so the blood picks up oxygen the whole way across. A shark has a cartilage skeleton and no swim bladder, so it has to keep water moving over its gills. And most sharks aren’t a danger to people at all.”
“A fish is a fish. It breathes with gills somehow. Sharks are just man-eaters.”
You demonstrate this unit through a fish anatomy and adaptation study where you locate each structure and explain what it does aloud — not a multiple-choice test. A criterion counts as mastered only when you can both find the structure and justify the adaptation 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.