Invertebrate animals account for the vast majority of species on earth. Although sometimes inconspicuous, invertebrates are vital members of ecological communities. They provide protein, important ecosystem services, biomedical and biotechnological products, and aesthetic value to humans. Today, many invertebrate populations are threatened by human activities. This course is designed to survey the extraordinary diversity of invertebrates, emphasizing their form and function in ecological and evolutionary contexts. BIO 261 must be taken concurrently.