BIOL 1002 Chapter : Chapter 23 Invertebrate Animals Part 1
Document Summary
In addition to these characteristics, as animals evolved, they developed more complex and organized bodies. Some of these increases in complexity and organization are: cellular specialization: vertebrate vs. invertebrate. Cephalization is the concentration of nervous tissue (including a brain and sensory organs) into a defined region (head) of the body. Segmentation is a body design in which similar repeating units are present. These and other characteristics are used to define the phyla of animals. Cellular specialization leads to the development of tissues, which then can lead to the combination of tissues into an organ. Figure 23-1 an evolutionary tree of some major animal phyla. Characteristic of sponges: sessile- non-moving, filter feeders, may reproduce sexually or asexually by budding and fragmentation, most species have an asymmetric body plan designed for water filtration. Three types of specialized cells are found in the sponge phylum. Epitthelial cells -outer covering layer (like a skin).
