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Marine Biology C—Engineered by the Ocean: Locomotion, Osmoregulation & Reproduction in Marine Vertebrates
by MonaA deep dive into three great problems every marine vertebrate must solve: how to move through water, how to keep salt and water in balance, and how to reproduce in the sea — culminating in the extreme physiology of deep divers.
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Moving Through Water
Lesson 1
Faster Than a Cheetah, Underwater
Water is 800 times denser than air and fights every movement, yet a sailfish hits speeds a sprinting cheetah would envy — so what does everyone misunderstand about how water pushes back?
StartLesson 2
Anguilliform to Thunniform: The Spectrum of Swimming Modes
Eels wiggle, tuna barely bend. Which strategy wins — and why does the answer depend on the mission?
Locked till you take the prior lessonLesson 3
Red Muscle, White Muscle, and the Hot-Bodied Tuna
Some fish broke the cold-blooded rule. Meet the muscle machinery that lets tuna outswim nearly everything.
Locked till you take the prior lessonLesson 4
The Buoyancy Problem: Swim Bladders vs. Oily Livers
Sinking is the default in the ocean. Compare two rival engineering solutions fish evolved to defy it.
Locked till you take the prior lessonLesson 5
Flippers, Flukes, and Underwater Flight
Penguins, sea turtles, seals, and whales all reinvented swimming from land-adapted bodies. Did they converge on the same answer?
Locked till you take the prior lessonThe Salt Problem
Lesson 6
Drinking Seawater to Survive: Marine Teleosts
Seawater dehydrates you — yet bony fish drink it constantly. How do they get away with it?
Locked till you take the prior lessonLesson 7
The Shark's Trick: Living Saltier
Sharks solved the salt problem completely differently — by filling their blood with a substance that should be toxic.
Locked till you take the prior lessonLesson 8
Crying Salt: Glands of Reptiles and Seabirds
Sea turtles really do 'weep' on the beach. Find out what those tears actually are.
Locked till you take the prior lessonLesson 9
Kidneys of the Deep: Marine Mammals and Freshwater Invaders
Whales never drink seawater — or do they? Trace where a dolphin's water actually comes from.
Locked till you take the prior lessonReproducing in the Sea
Lesson 10
The Million-Egg Gamble: Broadcast Spawning
A single cod releases millions of eggs, and almost all die. Why is this catastrophic-sounding strategy so successful?
Locked till you take the prior lessonLesson 11
From Eggs to Live Birth: The Evolution of Viviparity in Sharks
Some shark embryos eat their siblings in the womb. Explore the strange road from egg cases to live birth.
Locked till you take the prior lessonLesson 12
Nests, Heat, and Destiny: Marine Reptile and Seabird Reproduction
For a sea turtle, the temperature of the sand decides something astonishing about her hatchlings.
Locked till you take the prior lessonLesson 13
Milk in the Water: Marine Mammal Reproduction
How do you nurse a calf underwater, on the move, with predators circling? Whales found a way.
Locked till you take the prior lessonThe Deep Divers
Lesson 14
The Dive Response: Holding Your Breath Like a Seal
An elephant seal can dive for two hours on one breath. The secret isn't bigger lungs — it's stranger than that.
Locked till you take the prior lessonLesson 15
Pressure, Collapse, and the Sperm Whale's Descent
At 2,000 meters, pressure would crush a submarine hull design. How does a whale's body survive what steel cannot?
Locked till you take the prior lesson