Transcript Ch 9-View of Earth`s Past

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)
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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. Virginiaremains 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?
• 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
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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
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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