An Introduction to Invertebrates

1. Chapter 33 An Introduction to Invertebrates Questions prepared by Ruth BuskirkUniversity of Texas at Austin Michael DiniTexas Tech University

2. Why do sponges represent a separate lineage, distinct from all other animal phyla? • They are sedentary and resemble plants. • Most individuals are hermaphrodites. • They do not have specialized cell types. • They have only two layers of cells. • They lack true tissues.

3. Cnidaria includes groups with a variety of body forms, but all share which common feature? • All are filter feeders. • All are strong swimmers. • All have a gastrovascular cavity and tentacles. • All live in tropical oceans. • All reproduce mainly asexually.

4. The group known as Lophotrochozoa includes about 18 animal phyla and has a huge diversity of body forms. On what basis are all these animals thought to be in the same clade? • DNA sequences • embryo structure • body cavity • type of skeleton • arrangement of appendages

5. Among flatworms that are internal parasites, which of the following would be expected? • light-sensitive eyes • prolific asexual reproduction in a vertebrate host • limited to microscopic size • suckers or piercing mouthparts

6. The clam, snail, and octopus are all molluscs. The muscular foot of a snail is homologous to (i.e., derived from the same structure as) which one of these? • head of the octopus • shell of the clam • legs of the octopus • siphon tube of the clam • mantle of the clam

7. The evolutionary origin of extensive complexity in arthropod body plans is thought to be associated with which of these morphological changes? • the origin of a chitinous exoskeleton • the origin of numerous appendages • the specialization of diverse body segments • the addition of numerous identical body segments • the fusion of body segments and reduction of appendages

8. Which of these genetic changes is thought to have led to the increasing complexity of the arthropod body plan? • increased number of Hox genes for body segmentation • changes in regulation of Hox genes for body segmentation • increased number of Hox genes for appendages • changes in regulation of Hox genes for appendages • increased complexity in genes for exoskeleton arrangements

9. Free-living flatworms, roundworms, and segmented worms share all of the following traits except • bilateral symmetry. • three embryonic tissue layers. • presence of a digestive system. • digestive tract with mouth and anus. • muscle tissue and a hydrostatic skeleton.

10. All of the following were important contributions to the large adaptive diversity of insects except • diverse mouthparts for feeding on different substances. • multiple origins of wings in different insect groups. • expansion of flowering plant diversity. • invasion of many terrestrial habitats by insects. • diverse reproductive and social behaviors.

11. In addition to similarities in their molecular DNA, the phyla Echinodermata (including sea stars) and Chordata (including the vertebrates) share all of these except • bilateral symmetry as adult animals. • an endoskeleton. • their means of locomotion. • deuterostome development. • a true coelom.