Ch 9-View of Earth’s Past Objectives Summarize how scientist worked together to develop geologic column List major divisions of geologic time Summarize how evolution is related to geologic change Identify characteristics of Precambrian rock Identify major geologic and major biological developments during Paleozoic Era List periods of Mesozoic and Cenozoic Era Identify major geologic and biological developments during Mesozoic Era Identify major geologic and biological developments during Cenozoic Era

Geologic Column Geologic time scale-scale outlines development of Earth and life on Earth Used to describe sequence and length of this change Geologic column-ordered arrangement of rock layers based on relative ages of rocks in which oldest rocks are at bottom Use column to estimate age of rock layers, cannot be dated radiometrically Compare rocks w/ similar layers that have same fossils or same relative position Principle of faunal succession-group of fossil plants and animals occur in the geologic recorded in a definite and determinable order. A period of geologic time can be recognized by its respective fossils

Major Divisions of Geologic Time Earth’s history marked by major changes in Earth’s surface, climate, types of organisms Cenozoic Era (65.5 million yrs-present) Complex human societies develop Large carnivores appear 1st primates appear Woolly mammoths appear Mesozoic Era (251-146 million yrs) Flowering plants and modern birds appear Mass extinction ends Mesozoic Era Jurassic Period-Dinosaurs dominant life form

Paleozoic (542-299 million yrs) Pangaea comes together, mass extinction ends Era Shelled marine invertebrates appear Atmosphere reaches modern O2 rich state Seed bearing plants develop Pre-Cambrain Time (4.6 billion yrs) Earth forms Continental shields appear Fossils are rare Stromatolites are most common organism

Eons and Eras Eon-largest unit of geologic time 4 eons Hadean, Archean, Proterozoic, Phanerozoic 1st 3 in Pre-cambrain Phanerozoic divided into eras-Paleozoic, Mesozoic, Cenozoic

Periods and Epochs Periods-eras divided into shorter time units Usually named for the place where its characteristic fossils were first discovered Epochs-divided into smaller units of time Defined by occurrences of distinct fossils in fossil record

Sec 2-Precambrain Time and Paleozoic Era Define evolution Gradual development of new organisms from pre-existing organisms Heritable change in the characteristic w/in population from one generation to next Natural selection Evolution and Geologic Time Major geologic and climate changes can affect ability of some organisms to survive Sea level=coastal areas

Precambrian Time Earth 4.6 billion yrs old Formation of Earth ended 342 million yrs ago 88% of Earth’s history Record difficult to interpret Rocks severely deformed and altered by tectonic activity

Precambrian Rocks Shields-large areas of exposed Precambrian rocks Exist on every continent Result of volcanic activity, mt building, sedimentation, metamorphism Half of valuable mineral deposits in Precambrian rock-nickel, iron, gold, copper

Precambrian Life Lacked bones, fossils rare Folding, faulting, erosion destroyed most of fossils Stromatolites-reef like deposits formed by blue green algae Marine worms, jelly fish, single celled org

Paleozoic Era 545-251 million yrs ago-at beginning land masses were scattered than came together to form Pangaea Cambrian Period-life thrives in shallow, warm waters Trilobites-most common Cambrian inverts. Used as index fossils Brachiopods-group of shelled animals. 2nd most common animal in Cambrian Worms, jellyfish, snails, sponges

Ordovician Period-Trilobite populations dwindle Clamlike brachiopods and cephalopod mollusks become dominant Large number of corals appear Graptolites-tiny invert that flourished in oceans, primitive fish appear. No plant life on land Silurian Period-Verts and inverts marine life continue to thrive Echinoderms more common Eurypterids-scorpion like sea creatures Plants evolve on land Devonian Period-age of fishes Land plants-horsetails, ferns, seed bearing plants

Carboniferous Period-Climate warm, humidity extremely high Forests and swamps cover land Coal deposits in Penns, Ohio, W. Virginia-remains of forests Permian Period-mass extinction of large number of Paleozoic life forms Continents joined to form supercontinent of Pangaea-Appalachian Mts Fossils indicate reptiles and amphibians survived environmental changes-dominated Earth

Sec 3-Mesozoic and Cenozic Era What happened at the end of Permian Period? 90% of marine organisms and more than 70% land organisms died What is a mass extinction? An episode during which large numbers of species become extinct

Mesozoic Era Periods of Mesozoic Era-Triassic, Jurassic, Cretaceous 251-65.5 million yrs ago Age of Reptiles Pangaea broke up Sierra Nevada and Andes Mts formed. How?

Jurassic Period-dinosaurs dominant Triassic Period-dinosaurs appear, lush forests w/ cone bearing trees and cycads Ammonites serve as index fossil 1st mammals appear-small rodent like Jurassic Period-dinosaurs dominant Saurischians and Ornithischians 50 tons and 25 m long Flying reptiles common Modern bats Cretaceous Period-dinosaurs continue to dominate Tyrannosaurs rex-6 m tall, huge jaws w/ sharp teeth Plant life becomes sophisticated Angiosperms appear

Cretaceous-Tertiary Mass Extinction Ended in mass extinction No dino fossils found after this period Caused by environmental changes-result of movement of continents and increased volcanic activity Impact hypothesis-giant meteorite crashed into Earth 65 million yrs ago

Cenozoic Era 65.5 million yrs ago Age of Mammals Continents moved to present day position Alps and Himalayas formed by tectonic plates Dramatic changes in climate-continental ice sheets covered 1/3 of Earth’s land What did this lead to? Temps decreased

Periods Tertiary-time before last ice age Quaternary-time w/ last ice age and includes present Divided in 7 epochs Paleocene and Eocene-1st primates evolved, earliest ancestor of horse, fossils indicate first whales, small reptiles still flourish. Temps decreased Oligocene and Miocene-Himalayas formed, climate became cooler and drier, early mammals became extinct. Deer, pigs, horses, camels, cats, dogs flourished. Antarctic icecap formed, Mediterranean Sea filled and dried up several times

Pliocene Epoch-Bear, dog and cat families evolved into modern forms, herbivores flourished. Sea level fell due to increase in ice, C America land bridge formed Pleistocene Epoch-began 1.8 million yrs ago, ice sheets advanced and retreated several times. Earliest modern humans were discovered-hunters Holocene Epoch-began 11,500 yrs ago, as the last glacial period ended, sea levels rose due to increase in sea level, coastlines took modern shape, N American Great Lakes formed, modern humans developed agriculture, and tools