Home Page Overview Site Map Index Appendix Illustration About Contact Update FAQ

Anatomy of Animals


Sponges are mainly marine animals that make up the phylum Porifera. They are the most primitive of all animals. Comparing gene sequences (with other animals) suggests that they may be very close to the "Animal Eve" called urmetazoan. Tracing the root further back, it is found that the choanoflagellates (the single-celled ancestors) have possessed many of the genes
Sponge Sponge Anatomy necessary for multicellularity already. Their evolutionary steps are clearly demonstrated from single-celled aquatic protists to colonies and then appear as the collar cells in sponges. A sponge does not have anything in their bodies that can be called tissues or organs. Instead each type of sponge cell is responsible for a different activity to keep the sponge alive. Some sponges grow on rocks and are brightly colored. Sponges often are shaped like vases with a central cavity (Figure 02). Figure 03 shows the anatomy of the sponge. The internal structures are described in the followings.

Figure 02 Sponge
[view large image]

Figure 03 Sponge Anatomy [view large image]

Although the terminologies (and hence the functions) for the various systems are in close parallel to those for the human body, the composition and distribution are vastly different.

Go to Next Section
 or to Top of Page to Select
 or to Main Menu