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lecture 6

by: Jordyn

lecture 6 ISB 202

GPA 3.6
Appl Envir & Organismal Bio
Pamela Rasmussen

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Appl Envir & Organismal Bio
Pamela Rasmussen
Class Notes
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This 6 page Class Notes was uploaded by Jordyn on Friday February 27, 2015. The Class Notes belongs to ISB 202 at Michigan State University taught by Pamela Rasmussen in Winter2015. Since its upload, it has received 20 views.


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Date Created: 02/27/15
The history of life The rst cells may have originated by chemical evolution on a young earth 0 Life on earth is probably developed from nonliving materials Became ordered into aggregates capable of slef replication amp metabolism 0 All life today arises only by reproduction of preexisting life 0 Conditions on early earth very different from now Very little 02 oxgen then to attack complex molecules Lightning volcanoes UV more intense today Chemical amp physical processes on early earth probably produced simple cells 4 likely stages 0 1 Synthesis of small organics molecules 0 2 Joining of these small molecules 0 3 Origin of selfreplicating molecules 0 4 Packaging of these molecules into cells All are testable predictions The basic components of life gave been synthesized in labs 0 DNA not yet spontaneously synthesized 0 quotLife forcequot elusive Fossils preserved remnants or impressions left by organisms of past ages Fossil record ordered array in which fossils appear in rocks 0 Record the passing of geological time Fossils are usually preserved in sedimentary rock which appears in layers or strata Organic material in body usually decays rapidly o Mineralrich hard parts ex bones teeth shells may fossilize 0 Minerals from groundwater may seep into bodies replace organic material creating a cast Occasionally fossils retain organic material 0 Thin lms between layers of sandstone or shale Ex plant leaves millions of years old are still green Beetles from the Eocene c 50 mya are still iddescent o Pollen vary common fossils Hard organic cases resist degradation Trace fossils things left behind o Footprints burrows or other impressions in sediments made by the activities of animals 0 quotFossilized behaviorquot Where decomposition cannot occur entire body may be preserved o Resin amber 0 Ice longterm 0 Acid bogs Prokaryotes dominant from 3520 bya Earliest organisms almost certainly prokaryotes 0 Early on prokaryotes diverged into 2 main branches Bacteria and archaea Both thrive today 0 Early forms used very little oxygen Early prokaryote fossils mostly o Stromatolites Fossilized layered microbial mats Still being made in places Early prokaryote fossils mostly o Stromolites mats made by bacteria turned to stone Fossilized layered microbial mats Still being made in places 0 We can observe the same processes now that happened on early earth 0 Bacteria from ancient warm water vents Oxygen began accumulating in the atmosphere about 27 bya o 02 accumulation gradual until 22 bya then shot up to 10 of current values quotOxygen revolutionquot Due partly to photosynthesis Oxygen a waste product 0 Corrosive 02 had enormous impact on life May have boomed many prokaryotes Some survived in anaerobic oxygenfree habitats Other species evolved to use 02 Eukaryotic life began by 21 bya Eukaryotic cells 0 All other life forms than prokaryotes 0 Mostly larger more complex 0 Incorporated prokaryotes into their cells Evolved into cell organelles 0 1st eukaryote known from slightly after 02 revolution 12 bya Evolution of the rst bacteria oxygen revolution evolution of rst proka ryotes Cambrian explosion Elmea em nme mamrmr Ii refliesquot a r i V r A Eum m HullIt lu nr Fish microbei mt ll l1 Lil JIL am m m H m U Ema Ht r r q a ndings l n main mm found armri mt 2 nd radiation of eukaryotes produced most major animal groups in early Cambrian o Corals and sponges existed earlier 0 When most animals rst evolved hard parts Plants fungi amp animals colonized land c 500 mya Colonization of land a milestone in the history of life 0 Photosynthetic bacteria on damp terrestrial surfaces gt 1 bya 0 Complex life did not colonize land until c 500 mya First land plants simple lowgrowing Fungi colonized with plants as partners Diversi cation of plants created niches for other life 0 Planteating animals amp their predators o Greatly increased surface area for habitation 0 Protection form predators Terrestrial vertebrates evolved from shes o Amphibians from shes o Reptiles evolved from amphibians 0 Birds amp mammals evolved from different quotreptile groupsquot Tiktaalik rst shland animal 0 375 mya 0 Fish characters Scales gills ns quotFishpodquot characters Limbs ears Tetrapod amphibian characters Ribs neck lungs Process affecting number and types of species on earth biodiversity O O o Biodiversity species richness speciation minus extinction o Speciation Arisal and proliferation o Extinction Disappearance Three major factors affecting earth39s longterm patterns of speciation and extinction 0 Large scale movement of continents Continental drift Over millions of years 0 Gradual climate changes Caused by continental drift Slight shifts in earth s orbit sun s energy 0 Rapid climate change caused by natural catastrophes Large volcanic eruptions Mt Pinatubo Meteorite and asteroid showers Release od methane from ocean oor Extinction o The ultimate longterm fate of all species The vast majority of species c 999 that have existed since ife arouse 35 bya are extinct o Extinction rates Backdround extinction low 1miionyear Mass depletion moderate 35 in past 500 mya Mass extinction high 2 in past 500 mya Extinction and biodiversity Mass depletionsextinctions can result in adaptive radiations o Takes c 5 mya 0 Can t replace what is lost Extinction natural 0 Humans are causing much higher rates than background exUncUons Projected human population growth will cause mass depletionsextinction in next century A species may become extinct because 0 1 Habitat destroyed o 2 Environment changed in an unfavorable direction 0 3 Evolutionary changes by other species in community may impact it negatively Ex ate Precambrianearly Cambrian lack of predators Evolution ofjawed shelled organisms in Cambrian doomed defenseless earlier ones Extinction inevitable in a changing world Global extinction crises 0 When conditions changed very rapidly and disruptively 0 Most species died out o 2 severe mass extinctions Permian and Cretaceous mass extinctions o 35 mass depletions Permian mass extinction 250 m ya 0 90 of marine species went extinct o 75 of terrestrial species 0 Causes may include Disturbance to habitats due to the formation of Pangaea Earths single supercontinent Massive volcanic eruptions in Siberia o Warming of global climate Changes in ocean circulation Poising by hydrogen sul de gas ect o Resulted in empty niches o Diversi cation of some surviving groups Listersourous survived the Permian mass extinction and was very abundant and lead to mammals Triassic right after Permian birds rst evolved and dinosaurs but not a wide variety Then Jurassic wide variety Cretaceous got rid of dinosaurs o Wiped out more than dinosaurs The cretaceous KT mass extinction 65 mya o Kcretaceous Ttertiary Half of marine species Everything over 55 pound on land Many families of terrestrial plants and animals Nearly all dinosaur lineages except birds Pterosaurs ying reptiles Marine reptiles Ammonites Causes may include Cooling climate 0 Draining of shallow seas 0 Large volcanic eruptions in India 0 Asteroid impact This was by far the most important Dust clouds blotted out the sun so little photosynthesis could occur 000 O The upside 0 Mass extinctions create opportunities for survivors Survival may be due to adaptive qualities or luck Survivors become the stock for new radiations Fill biological roles vacated by the extinctions For mammals juts a few lineages survived the KT event but they quickly gave rise to a diversity of groups


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