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Class Sarcopterygii
- The lobe-fins have muscular pelvic and pectoral fins
- Three lineages survive and include coelacanths, lungfishes, and tetrapods
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changes made in class Sarcopterygii
- Old lineages
- Transitional fossils
- Fins shifting to legs
- Gills to lungs
- Coelacanth fossils found in more than 350 MYA
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Tetrapods (4 feet)
- Derived Characters of Tetrapods
- –Tetrapods have some specific adaptations:
- Four limbs, and feet with digits
- Ears for detecting airborne sounds
- In one lineage of lobe-fins, the fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life
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Amphibia
- Amphibians are represented by about 6,150 species of organisms in three orders
- Amphibian means “both ways of life,” referring to the metamorphosis of an aquatic larva into a terrestrial adult
- Most amphibians have moist skin that complements the lungs in gas exchange
- Fertilization is external in most species, and the eggs require a moist environment
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Amphibian Orders
- Order Urodela includes salamanders, which have tails
- Order Anura includes frogs and toads, which lack tails
- Order Apoda includes caecilians, which are legless and resemble worms
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Reasons for amphibian decline around the world
- Chrytid fungus
- Habitat loss
- Climate change
- Trematodes (cause deformities)
- Pollution and chemicals
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Amniotes
- Amniotes are a group of tetrapods whose living members are the reptiles, including birds, and mammals
- Derived Characters:
- –amniotic egg, which contains membranes that protect the embryo–relatively impermeable skin
- –ability to use the rib cage to ventilate the lungs
- The extra-embryonic membranes are the amnion, chorion, yolk sac, and allantois
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Reptilia
- The reptile clade includes the tuataras, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs
- Derived Characters:
- –Reptiles have scales that create a waterproof barrier
- –They lay shelled eggs on land
- Most reptiles are ectothermic
- Birds are endothermic
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ectothermic
absorbing external heat as the main source of body heat
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endothermic
capable of keeping the body warm through metabolism
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Lepidosaurs
(reptilia)
The lepidosaurs include tuataras, lizards, and snakes
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archosaurs
lineage produced the crocodilians, pterosaurs, and dinosaurs
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Turtles
- All turtles have a boxlike shell made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs
- Some turtles have adapted to deserts and others live entirely in oceans or ponds and rivers
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crocadilians
(alligators and crocodiles) belong to an archosaur lineage that dates back to the late Triassic
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birds
Birds are archosaurs, but almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight
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bird characteristics
- The major adaptation is wings with keratin feathers
- Lack of a urinary bladder
- Females with only one ovary
- Small gonads
- Loss of teeth
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Class mammalia
- Mammals are represented by more than 5,300 species
- By the early Cretaceous, the three living lineages of mammals emerged: monotremes, marsupials, and eutherians
- Mammals did not undergo a significant adaptive radiation until after the Cretaceous
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Derived characters of Mammalia
- Mammary glands, which produce milk
- Hair
- A larger brain than other vertebrates of equivalent size
- Differentiated teeth
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Monotremes
are a small group of egg-laying mammals consisting of echidnas and the platypus
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Marsupials
- include opossums, kangaroos, and koalas
- –The embryo develops within a placenta in the mother’s uterus
- –A marsupial is born very early in its development
- –It completes its embryonic development while nursing in a maternal pouch called a marsupium
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Eutherians
- Compared with marsupials, eutherians have a longer period of pregnancy
- Young eutherians complete their embryonic development within a uterus, joined to the mother by the placenta
- Molecular and morphological data give conflicting dates on the diversification of eutherians
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Primates
- The mammalian order Primates includes lemurs, tarsiers, monkeys, and apes
- are members of the ape group
- Most primates have hands and feet adapted for grasping
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Hominids
- The study of human origins is known as paleoanthropology
- Hominids are more closely related to humans than to chimpanzees
- Paleoanthropologists have discovered fossils of about 20 species of extinct hominids
- Hominids originated in Africa about 6–7 million years ago
- Early hominids had a small brain but probably walked upright
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humans
A number of characters distinguish humans from other apes:
- –Upright posture and bipedal locomotion
- –Larger brains
- –Language capabilities and symbolic thought
- –The manufacture and use ofcomplex tools
- –Shortened
- –Shorter digestive tract
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