Biology / Unit 10 Bio 2217 short lesson, about 20 seconds
Diploblastic versus Triploblastic Body Plans
Captions available
The idea
A diploblastic animal forms two germ layers, ectoderm and endoderm; a triploblastic animal forms three, adding mesoderm between them.
In practice
A jellyfish is diploblastic, lacking mesoderm-derived organs; an earthworm is triploblastic, with mesoderm-derived muscle and internal organs.
Where people slip
Mesoderm's presence, not general body size, is what separates diploblastic from triploblastic lineages — some triploblastic animals are smaller than some diploblastic ones.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for Biology