The Most Ancient Branch Point in Animal Phylogeny is That

Question

The most ancient branch point in animal phylogeny is that between having
A) radial or bilateral symmetry.
B) a well-defined head or no head.
C) diploblastic or triploblastic embryos.
D) true tissues or no tissues.
E) a body cavity or no body cavity.

Accepted Answer

The most ancient branch point in animal phylogeny is between those that have true tissues, such as muscles and nerves, and those that do not. This defines the distinction between the Porifera (sponges), which lack true tissues, and all other animals. The other choices are not as fundamental in defining the branching points in animal phylogeny.