• 18.16 Lampreys are vertebrates that lack hinged jaws – Lampreys represent the oldest living lineage of

vertebrates• Suspension feeders in freshwater streams• Have jawless mouth with rasping tongue

– The vast majority of living vertebrates have two-part jaws connected by a hinge

– Jaws likely evolved from anterior pharyngeal slits

•18.17 Jawed vertebrates with gills and paired fins include sharks, ray-finned fishes, and lobe-fins

– Three lineages of jawed vertebrates with gills and paired fins are commonly called fishes

– Chondrichthyans have changed little in 300 million years

• Include sharks and rays• Flexible skeleton made of cartilage• Lateral line system of sensory organs

– The ray-finned fishes include familiar fishes such as tuna, trout, and goldfish

• Skeleton reinforced with a hard matrix of calcium phosphate

• Operculi that move water over the gills• Buoyant swim bladder

– Lobe-finned fishes have muscular fins supported by bones

• Three surviving lineages including one that gave rise to terrestrial vertebrates

•18.18 Amphibians were the first tetrapods—vertebrates with two pairs of limbs

– Amphibians were the first tetrapods with limbs allowing movement on land

• Possibly evolved from lobe-fins during the Devonian period

• Became very widespread during the Carboniferous period

• Include salamanders, frogs, and caecilians

– The “double life” of amphibians refers to the metamorphosis of many frogs

• Larval stage (tadpole): a legless, aquatic algae-eater with gills, a lateral line system, and a long, finned tail

• Adult: a terrestrial insect eater with four legs and air-breathing lungs

– Most amphibians are found in damp habitats, where their skin functions in gas exchange

– Amphibian skin usually contains poison glands that function in defense

• 18.19 Reptiles are amniotes—tetrapods with a terrestrially adapted egg– Reptiles include lizards, snakes, turtles, crocodiles,

birds, and a number of extinct groups such as dinosaurs – The major derived characteristic of the clade containing

reptiles and mammals is the amniotic egg• Embryo develops with a protective, fluid-filled sac• Enabled reptiles to complete their life cycles on land

– Reptile adaptations for terrestrial life in addition to the amniotic egg include

• Scaly, waterproof skin that keeps body from drying out• Lungs for obtaining oxygen• Ecothermic metabolism (in nonbirds)

– Dinosaurs, the most diverse reptiles, included some of the largest animals ever to inhabit land

• May have been endothermic• Died out 65 million years ago but left birds as descendants

•18.20 Birds are feathered reptiles with adaptations for flight

– Birds likely evolved from a lineage of small, two-legged dinosaurs called theropods

• Evidence from fossils such as Archaeopteryx

LE 18-20aWing claw(like dinosaur)

Feathers

Long tail withmany vertebrae(like dinosaur)

Teeth(like dinosaur)

– Nearly every part of the body of most birds reflects adaptations that enhance flight

• Weight-reducing features such as few teeth, strong but light bones

• Feathers• Large, powerful breast muscles• Endothermic metabolism, highly efficient circulatory

system• Acute vision

– Birds have relatively large brains and complex behaviors

• Male and female cooperation in raising young• Migration

– A few flightless species of birds exist (example: emu)

•18.21 Mammals are amniotes that have hair and produce milk

– Main adaptive features of mammals • Hair, which provides insulation• Mammary glands, which produce milk • Endothermic metabolism• Efficient respiratory and circulatory systems• Differentiation of teeth for different foods• Large brain, long period of parental care allowing for learning

– There are three main groups of living mammals• Monotremes lay eggs

– Examples: echidna, duck-billed platypus

• The embryos of marsupials and eutherians are nurtured by the placenta within the uterus

– Marsupials complete development outside the mother’s body

– Eutherians (placental mammals) complete development before birth