chapter 41 section 1

Question 1

vertebral column

Answer 1

spine

Question 2

cranium

Answer 2

skull

Question 3

gill arch

Answer 3

skeletal elements that support the pharynx

Question 4

mammal

Answer 4

class mammalia
have hair and nurse their young with milk

Question 5

vertebrate characteristics

Answer 5

postanal tail
pharyngeal pouches
endoskeleton

Question 6

skates belong to the class

Answer 6

chondricthyes

Question 7

jawless fish

Answer 7

hagfish

Question 8

earliest vertebrates were

Answer 8

jawless fishes with heavy, bony scales

Question 9

The evolution of paired fins was important to early fishes because paired fins

Answer 9

increased the stability and maneuverability of the fishes

Question 10

Jaws are thought to have evolved from the

Answer 10

first pair of gill arches

Question 11

Compare and contrast modern jawless fishes with those that lived 500 million years ago

Answer 11

both groups lack jaws and paired fins. both have cartiliginous skeletons.
Early ones were covered with heavy, bony scales

Question 12

Compare and contrast the skin of amphibians with the skin of reptiles.

Answer 12

The skin of amphibians is thin and permeable to

gases and water; the skin of reptiles is dry and scaly

Question 13

Name the class to which horses belong, and describe two major characteristics of the animals in
that class

Answer 13

Horses belong to the class Mammalia; animals in
that class have hair and nurse their young.

Question 14

What two important evolutionary events occurred in the acanthodians, or spiny fishes about 440 million years ago?

Answer 14

jaws and paired fins appeared

Question 15

Explain why the class Chondrichthyes contains many more species than
the class agnatha

Answer 15

the jaws and paired fins of fishes in the class Chondrichthyes allow them to diversify into numberous species and be better predators