Final answer:
The structural differences between Porifera and Cnidaria include a porous, simple body versus radial symmetry with nematocysts, respectively, with Cnidaria showing higher complexity such as a digestive system and two distinct body forms.
Step-by-step explanation:
When comparing the structural differences between Porifera and Cnidaria, there are several distinctions to be made:
- Porifera, commonly known as sponges, have a porous body lacking true tissues and organs. Their body is supported by an endoskeleton of spicules and spongin fibers, and their cells are organized into a simple structure called a pinacoderm.
- Cnidaria, which includes jellyfish, corals, and sea anemones, exhibit radial symmetry and possess two main tissue layers that sandwich a noncellular mesoglea. Exclusive to Cnidarians are nematocysts, which are specialized stinging cells used for capturing prey and defense.
Furthermore, Cnidaria exhibit a more complex organization than Porifera with a well-defined digestive system and the ability to carry out extracellular digestion. They also feature two general body forms found in the phylum: the sessile polyp and the free-swimming medusa.