In Porifera (sponges), how are the ovum and blastula not organs?

Question

I’m in a “principles of animal biology” class, and my lab TA doesn’t know why. They seem to meet the requirements… Can someone please explain? I can’t stop thinking about it.

In: 5

Answer 1

Organs are a collection of tissues joined in a structural unit to serve a common function. Eggs (ovum) are not organs; they are not collection of tissues joined in a structural unit to serve a common function. Cells produced during the development of an embryo by repeated cleavage of a fertilized egg (blastula) are not organs; they are not a collection of tissues joined in a structural unit to serve a common function.