Biology / Unit 10 Bio 2213 short lesson, about 20 seconds
Animal Kingdom Defining Features
Captions available
The idea
Animals are multicellular heterotrophs lacking cell walls, most reproducing sexually and passing through a blastula stage in embryonic development.
In practice
A sponge and a human both develop from a hollow blastula, share no cell wall, and get nutrients by consuming other organisms.
Where people slip
"Multicellular heterotroph" alone does not define animals — fungi are multicellular heterotrophs too, but feed by absorption, lacking a blastula.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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