Chapter 31

A body cavity that separates the digestive system from the body wall but is not completely lined with mesoderm is called a: a. schizocoelom. b. mesentery. c. peritoneum. d. pseudocoelom. e. hydrostatic skeleton.

Protostomes and deuterostomes typically differ in: a. their patterns of body symmetry. b. the number of germ layers during development. c. their cleavage patterns. d. the size of their sperm. e. the size of their digestive systems.

The nematocysts of cnidarians are used primarily for: a. capturing prey. b. detecting light and dark. c. courtship. d. sensing chemicals. e. gas exchange.

Which organ system is absent in flatworms (phylum Platyhelminthes)? a. nervous system b. reproductive system c. circulatory system d. digestive system e. excretory system

Which part of a mollusk secretes the shell? a. visceral mass b. radula c. trochophore d. head-foot e. mantle

Which phylum includes the most abundant animals in soil? a. Nematoda b. Rotifera c. Mollusca d. Annelida e. Brachiopoda

Which body region of an insect bears the walking legs? a. head b. carapace c. abdomen d. thorax e. trunk

Ecdysis refers to a process in which: a. bivalves use siphons to pass water across their gills. b. arthropods shed their old exoskeletons. c. cnidarians build skeletons of calcium carbonate. d. rotifers produce unfertilized eggs. e. squids escape from predators in a cloud of ink.

What is the major morphological innovation seen in annelid Worms? a. a complete digestive system b. image-forming eyes c. a respiratory system d. an open circulatory system e. body segmentation

Many invertebrate species are hermaphroditic. What selective advantages might this characteristic offer? In what kinds of environments might it be most useful?

What are the relative advantages and disadvantages of radially symmetrical and bilaterally symmetrical body plans?

People who eat raw clams and oysters harvested from sewage-polluted waters often develop mild to severe gastrointestinal infections. These mollusks are suspension feeders. Develop a hypothesis about why people who eat them raw may be at risk.