BIOL 1002 : Exam 2 Notes
Document Summary
Chapter 23: animals possess all of the following characteristics: They are motile at some point in the life cycle. They are able to respond rapidly to external stimuli: lack of tissues separates sponges from all other animals. Tissues are groups of similar cells that carry out a specific function (muscle) Sponges are the only modern-day animals that lack tissues. Individual cells in sponges may be specialized, but they act independently and are not organized into true tissues: animals with tissues exhibit either radial or bilateral symmetry. Symmetrical animals have an upper (dorsal) surface and a lower (ventral) surface. Phylum porifera: sponges have a simple body plan. Sponges belong to the phylum porifera and are found in most marine environments. The sponge body is perforated by tiny pores through which water passes, and by fewer, large openings through which water is expelled.
