In a tube-within-a-tube body plan, what is the interior tube derived from?a. ectodermb. mesodermc. the coelomd. endoderm

The table below lists the common names of the nine animal phyla surveyed in this chapter. For each phylum, list the key characteristics and some representatives.

Which synapomorphy (shared, derived trait) distinguishes animals as a monophyletic group, distinct from choanoflagellates?a. multicellularityb. colonialityc. heterotrophyd. movement

The distinction between sponges and other animal phyla is based mainly on the absence versus the presence ofa. a body cavity.b. a complete digestive tract.c. mesoderm.d. tissues.

Identify the pattern of embryonic development shown in each drawing below and name the phylum (or phyla) that exhibit this pattern.

Which of the following was probably an important factor in bringing about the Cambrian explosion? (A) the movement of animals onto land (B) an increase in the concentration of atmospheric nitrogen (C) the emergence of predator-prey relationships (D) the origin of bilaterian animals

Which of the following was probably the least important factor in bringing about the Cambrian explosion?a. the emergence of predator-prey relationshipsb. an increase in the concentration of atmospheric oxygenc. the movement of animals onto landd. the origin of Hox genes

Bilateral symmetry in animals is best correlated witha. an ability to see equally in all directions.b. the presence of a skeleton.c. motility and active predation and escape.d. adaptation to terrestrial environments.

True or false? New major animal body plans have continued to evolve since the Cambrian about 550 million years ago.