Bio 1B Lecture Outline please print and bring along Fall 2007 B D Mishler Dept of Integrative Biology 2 6810 bmishler berkeley edu Evolution lecture 9 Fossils Mesozoic and Cenozoic Nov 26th 2007 251 Myr Mesozoic Era Triassic Jurassic Cretaceous Dinosaurs flying reptiles marine reptiles mammals Fig 34 32 7th Fig 34 30 6th birds Fig 34 29 7th Fig 34 27 6th and flowering plants appear insects dinosaurs and marine invertebrates diversify Diversification of land plants increasing diploid sporophyte dominance telome theory to explain increasing division of labor and complexity in the sporophyte origin of seeds origin of flower In some cases an early diversification of major group was followed by later winnowing decimation and diversification insect diversification coevolution with flowers mutual adaptive radiation Illustrates another example of the importance of coevolution as a general principle icthyosaurs marine reptiles of the Mesozoic plesiosaurs marine reptiles of the Mesozoic pterosaurs flying reptiles of the Mesozoic diapsids two openings on each side of skull lizards snakes archosaurs and their descendants crocodiles pterosaurs dinosaurs and birds synapsids single opening low on each side of skull mammal like reptiles and mammals dinosaurs distinguished from other diapsid reptiles by erect gait straight legs attached underneath their bodies archaeopteryx classified as the first bird 150 Myr Distinguishing characteristics were feathers asymmetric wings and an ability to glide dinosaurs with proto feathers and feathers have recently been discovered Mass extinction at end of Cretaceous dinosaurs pterosaurs icthyosaurs and plesiosaurs extinct Pangaea breaking up climate changing sea level changing meteorite impact Fig 26 9 7th Fig 25 6 6th Evolution 9 pg 1 Luis Alvarez UC Berkeley discovered that the usually rare element iridium is abundant in a thin layer of rocks that mark the end of the Cretaceous and proposed that a large meteorite or asteroid at least 10 km wide struck earth at that time and caused the Cretaceous extinction Almost all large vertebrates and many other species went extinct At the end of the Cretaceous 65 mya called the K T boundary almost all large vertebrates dinosaurs pterosaurs plesiosaurs many tropical vertebrates most plankton and many tropical invertebrates especially reef dwellers became extinct and many land plants were severely affected Surviving groups radiated to become the dominant flora and fauna today Surviving groups including insects mammals birds and flowering plants on land and fishes corals and mollusks in the ocean went on to diversify tremendously soon after the end of the Cretaceous It was a major event in the history of life that profoundly affected life on earth since No one doubts that the world would be very different had this mass extinction not occurred The probably impact crater has been located in Mexico Later the impact crater in Yucatan was found near the port city of Progresso and is known as the Chicxulub structure The crater is 200 300 km in diameter and lies beneath 1100 m of limestone It was known to the Mexican national petroleum company now Pemex After the Berkeley group suggested an impact at the K T boundary Pemex scientists recognized that their observations were consistent with the idea that they had found the impact crater Roughly 200 000 km 3 of material was ejected and vaporized as a result of the impact 65 Myr Cenozoic Era Tertiary Paleocene Eocene Oligocene Miocene Pliocene Quaternary 1 8 Myr Pleistocene Holocene Recent 10 000 yrs Diverse forms of mammals birds flowering plants and insects Major radiation of mammals birds and pollinating insects By end of Eocene mammals of every size and lifestyle had appeared with many similar to modern forms and others very different Radiation of angiosperms including appearance of grasses Evolution 9 pg 2 Humans Homo sapiens appear in the Pleistocene Mass extinction at end of Pleistocene primarily non marine many large mammals extinct Transitional Fossils Many examples of transitional fossils are known e g Paleozoic fish to amphibians tetrapods Fig 34 19 7th Fig 34 16 6th amphibians to reptiles Mesozoic mammal like reptiles to mammals dinosaurs to birds wasps to ants Cenozoic land mammals to whales Fig 22 18 7th Fig 22 17 6th Primate evolution The two major groups of the primates are the prosimians and the anthropoids Fig 34 38 7th Fig 34 35 6th prosimians premonkeys lemurs of Madagascar lorises pottos and tarsiers that live in tropical Africa and southern Asia anthropoids monkeys apes and humans anthropoid evolution binocular vision larger brain opposable thumb complex social interactions hominoids apes and hominids hominids humans and their direct ancestors hominid genera Ardipithicus Australopithecus and Homo hominid evolution bipedalism enlargement of brain and cultural evolution At various times a number of different hominid species apparently coexisted Homo habilis used tools consistently Homo erectus used fire Homo neanderthalensis Neanderthals Homo sapiens Cro Magnons modern humans Early hominids unlike chimps and gorillas lived in relatively dry areas Evolution 9 pg 3 The oldest hominid fossils date to 6 mya and are very similar to chimpanzees That date is consistent with estimated time of their most recent common ancestor based on DNA sequence comparisons suggesting that earlier specimens if they are found are common ancestors Fig 34 38 on p 710 Evolution 9 pg 4
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