1. 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

2. 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

3. 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 ( million yrs)
Flowering plants and modern birds appear
Mass extinction ends Mesozoic Era
Jurassic Period-Dinosaurs dominant life form

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. Paleozoic Era
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

13. 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

14. 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

15. 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

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

17. 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

18. 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

19. 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

20. 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

21. 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