Biology / Unit 12 Bio 2725 short lesson, about 20 seconds
Exoskeleton and Endoskeleton Size Limits
Captions available
The idea
An exoskeleton must thicken sharply as body weight increases, since doubling size roughly increases weight eightfold, capping most exoskeleton-bearing animals at a small size; an endoskeleton scales more efficiently since muscles attach outside it.
In practice
Insects and crustaceans stay small under their exoskeletons, while endoskeleton-bearing whales grow to enormous size.
Where people slip
Molting lets an exoskeletal animal grow only in stages, not continuously.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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