In this chapter you will review key events in the evolution of invertebrates, particularly their patterns of development. You will also compare their different strategies for carrying out life functions.

In this chapter, you will: explain how evolutionary relationships are shown on a phylogenetic tree compare the development of protostomes and deuterostomes compare acoelomate, pseudocoelomate, and coelomate animals discuss the ways in which different invertebrate phyla carry out their essential life functions describe the evolution of various body systems in invertebrates