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Mesozoic Era .docx

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BIOL 4150
Scott Brandon

The Permian (297-251 mya) o During the Permian period, the continents united to form the supercontinent Pangaea o Massive volcanic eruptions: ash blocked sunlight and cooled the climate => largest glaciers in Earth’s history. o By the end, reptiles greatly outnumbered amphibians. o The lineage leading to mammals diverged from one line of reptiles. Bony fishes radiated in the oceans. o Mass extinction at end: 96% species lost (volcanoes, meteorite & ocean turnover implicated) o At the end of the Permian, a large meteorite crashed into northwestern Australia. o Volcanic eruptions poured lava into the oceans, which depl2ted O in deep oceans. Oceanic turnover then carried the depleted water to the surface where it released2toxic2CO and H S. o O2concentrations dropped to about 12 percent—most animals would have been unable to survive at elevations above 500 m. o About 96% of all species on Earth became extinct. Mesozoic Era (251–65 mya) o At the start of the Mesozoic era (248 mya), the few surviving organisms found themselves in a relatively empty world. o Pangaea slowly separated, glaciers melted, and shallow inland seas formed. o Life proliferated and diversified. o Earth’s biota diversified and became distinct on each continent (previously more homogeneous).  Earth’s biota became increasingly provincialized: that is distinct terrestrial biotas evolved on each continent o By end of the era, the continents were close to their present positions and many organisms looked similar to those living today o Divided into The Triassic, The Jurassic, and The Cretaceous The Triassic (251-200 mya) o Pangaea began to break apart o Vertebrate & invert. lineages became more diverse. o Conifers and seed ferns became the dominant trees. o Frogs and turtles appeared. o Rise of reptiles, which gave rise to dinosaurs, crocodilians, and birds. o Mass extinction at end: 65% of the species lost. o A mass extinction at the end linked to a meteorite impact in present-day Quebec. The Jurassic (200-145 mya) o Two large continents: Laurasia (Laurentia (= NA) + Eurasia) & Gondwana (after region in India, contained India + all southern continents). o Ray-finned fishes began the great radiation that culminated in their dominance of the oceans. o Salamanders and lizards first appeared. o Flying reptiles! (pterosaurs) o Dinos: bipedal predators and quadrupedal herbivores. o Mammals first appeared. o Plant evolution continued with the emergence of the flowering plants that dominate Earth’s vegetation today The Cretaceous (145-65 mya) o Gondwana breaking apart, and a continuous ocean circled the tropics. Sea levels were high & Earth was warm and humid. o Flowering plants (angiosperms) evolved from gymnosperms. Many groups of mammals had evolved, but most were small. First snakes! o Mass extinction at end of Cretaceous; it was probably caused by a large meteorite colliding with Earth. o All vertebrates larger than about 25 kg in body weight, including all of the dinosaurs, apparently became extinct as a result of this impact. Cenozoic (65 mya) o By the early Cenozoic era (65 mya), the continents were close to their present-day positions; however, Australia was still a
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