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• 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