Vertebrates and tunicates share a. jaws adapted for feeding. b. a high degree of cephalization. c. an endoskeleton that includes a skull. d. a notochord and a dorsal, hollow nerve cord.

Living vertebrates can be divided into two major clades. Select the appropriate pair. a. the chordates and the tetrapods b. the urochordates and the cephalochordates c. the cyclostomes and the gnathostomes d. the marsupials and the eutherians

Unlike eutherians, both monotremes and marsupials a. lack nipples. b. have some embryonic development outside the uterus. c. lay eggs. d. are found in Australia and Africa.

Which clade does not include humans? a. synapsids b. lobe-fins c. diapsids d. osteichthyans

As hominins diverged from other primates, which of the following appeared first? a. reduced jawbones b. an enlarged brain c. the making of stone tools d. bipedal locomotion

Which of the following could be considered the most recent common ancestor of living tetrapods? a. a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebrates b. an armored, jawed placoderm with two pairs of appendages c. an early ray-finned fish that developed bony skeletal supports in its paired fins d. a salamander that had legs supported by a bony skeleton but moved with the side-to-side bending typical of fishes

EVOLUTION CONNECTION Living members of a vertebrate lineage can be very different from early members of the lineage, and evolutionary reversals (character losses) are common. Give examples that illustrate these observations, and explain their evolutionary causes.