chapter 41 reptiles
DESCRIPTION
Chapter 41 Reptiles. Section 1 Origin & Evolution of Reptiles. History of Reptiles. Fossils & comparative anatomy suggest that reptiles arose from amphibians Earliest reptiles date 359-299 million years ago Many insects during this time period which served as food. History of Reptiles. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 41ReptilesSection 1
Origin & Evolution of Reptiles
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History of Reptiles• Fossils & comparative anatomy
suggest that reptiles arose from amphibians
• Earliest reptiles date 359-299 million years ago
• Many insects during this time period which served as food
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History of Reptiles• Around 299 to 251 million years
ago- reptiles dominant land vertebrates
• Pangaea- super continent
• Interior of Pangaea was dry- suitable for reptiles- why?
• End of Permian Period (299 MYA)- mass extinction
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History of Reptiles• Mesozoic era (251-66 MYA)- Age
of the Reptiles
• Nearly all large vertebrates were reptiles
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Evolution of Dinosaurs• 235 MYA- dinosaurs- group of
extinct reptiles
• Evolved from thecodonts- extinct group of crocodile-like reptiles
• Evolution was affected by the break-up of Pangaea
• Climates changed- some died, some flourished
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Thecodont
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Triassic Dinosaurs• 235 MYA- oldest dinosaur fossils-
Triassic Period
• Successful because-
• 1. legs positioned under body provided support
• 2. well-adapted to dry conditions
• 3. Last mass extinction wiped out other animals
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Triassic Dinosaurs• Evidence suggests asteroid
impacts contributed to mass extinction
• Canada, France, Ukraine, and Minnesota have evidence to support this theory
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Jurassic & Cretaceous Dino• Jurassic- golden age of dinosaurs-
variety and abundance
• Sauropods- largest land animals of all time
• Theropods- powerful legs and short arms (T. Rex)
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Dinosaur Diversity• Land dinosaurs
• Mesozoic reptiles- pterosaurs- evolved the ability to fly
• Ichthyosaurs & plesiosaurs- lived in the oceans- resembled bottle-nose dolphins
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Ichthyosaurs
plesiosaurs
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Extinction of Dinosaurs• Scientists still have many
questions, but they have some ideas and evidence as to why the dinosaurs are extinct
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Asteroid Impact Hypothesis• Asteroid impact hypothesis-
suggests huge asteroid hit Earth and formed a crater on the Yucatan Peninsula in southern Mexico
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Asteroid Impact Hypothesis
• Caused much dust that covered Earth and changed climate
• Sediments during Cretaceous time- high iridium- very rare metal (abundant in asteroids)
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Multiple Impact Hypothesis• Proposes multiple asteroids hit Earth• Unfavorable environmental
conditions because of this event• Paleontologist- Gerta Keller-
provided evidence to support this hypothesis
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Success of Reptiles• Order Chelonia- turtles & tortoises• Order Squamata- lizards & snakes• Order Crocodilia- alligators &
crocodiles• Order Rhynchocephalia- tuataras• Found on every continent except
Antarctica
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Modern Reptiles• Turtles have changed very little in
structure
• Tuataras- lizard-like reptiles
• Snakes & lizards- majority of reptiles
• Crocodiles & alligators changed very little- decedents of thecodonts
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Modern Reptiles• Crocodiles resemble birds
especially by looking at the structure of their heart (four-chambered)
• Crocodiles take care of young• Scientists suggest birds are direct
decedents of reptiles
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Amniotic Egg• Amniotic egg- encase embryo in
a secure, self-contained aquatic environment
• More secure than jelly-like amphibian eggs
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Amniotic Egg• Amnion- thin membrane enclosing
the fluid in which the embryo floats
• Yolk sac- encloses the yolk, fat-rich food supply for developing embryo
• Allantois- stores nitrogenous wastes produced by embryo
• Chorion- surrounds all other membranes and protects embryo
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Amniotic Egg• First occurred in reptiles, but also
is found in birds and mammals
• Strong evidence suggests that reptiles, birds, and mammals evolved from a common ancestor
• The eggs of some reptiles & nearly all mammals lack shells & embryo develops in mother’s body
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Water-tight skin• What type of skin do amphibians
have? Why do they have this type?
• Reptiles have thick, dry, scaly skin that prevents water loss
• Keratin- same protein that forms your fingernails & hair
• Lipids & proteins in the skin help make it water-tight
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Respiration & Excretion• All reptiles have lungs for gas
exchange
• All reptiles have bodies adapted to conserve water
• Tissues for gas exchange located in body- kept moist
• Reptiles lose small amounts of water in urine (uric acid)
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REVIEW!!!• Explain the importance of iridium found in
sediments from the end of the Cretaceous period.
• Summarize the two asteroid impact hypotheses.
• Describe three characteristics that contribute to the success of reptiles on land.