tracing e volutionary history
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Tracing Evolutionary
HistoryCHAPTER 15
15.1O Fossils chronicle the evolutionary
timelineO Eras in geologic timeO PrecambrianO PaleozoicO MesozoicO Cenozoic
Precambrian EraO 4.6 billion ya- 542 mya
O First fossils- prokaryotic cells (3.5 billion ya)
O Diverse invertebrates (600 mya) and algae
O Oxygen builds up in our atmosphere as the result of photosynthetic bacteria
Paleozoic eraO 542 mya-251myaO Cambrian explosion – many new
animalsO Colonization of land by arthropods
and land plants O FishO Tetrapods (amphibians)O Seed plants, Reptilian adaptive
radiationO Major extinction of many organisms
Mesozoic EraO 251 mya-65myaO Cone bearing plantsO Radiation of dinosaurs O Origin of mammals O Flowering plants O Major dinosaur extinction at end of
era
Cenozoic EraO 65 mya-present O Radiation of birds and mammalsO Origin of primates O Origin of hominids O Ice Ages
15.3 Continental driftO 1912- Alfred Wegener suggested that
all the land masses were once a single mass called Pangea
O Pangea broke apart and the continents drifted to there current locations creating geographic isolation
15.5 Mass Extinctions O Permian mass extnction (boundary
between Paleozoic and Mesozoic) 96% of all marine life O Volcanic eruption in Siberia ?
O Creataceous mass exntinction – dinosaur extinction O Asteroid collision? Climate change ?
Convergent EvolutionO Likeness suggests
relationships . . .however some likeness is the result of living in a similar environement NOT common ancestry
O Streamlined appearance of both whales (mammals) and sharks (cartilage fish)
Scientific naming O Linneaus – 18th century – Latin naming
system O DomainO KingdomO PhylumO ClassO OrderO FamilyO Genus + species = organism’s scientific
name
15.8 Cladistics O Forming family trees based on
shared traits O New branches have derived traits O “family trees” – cladograms
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