Eras of Earth`s History
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Transcript Eras of Earth`s History
Eras of Earth’s History
EQ: What causes changes in the
Earth? How does knowing the past
give us a VISION for the future?
Precambrian Time Eon
Precambrian Time Eon
4.6 billion years ago-545 million years ago
Information about this time on Earth is
SCARCE
Rocks are buried deep within Earth’s Crust
Information on rocks damaged or destroyed by
Earth’s inner heat and pressure of other rock
layers
Moon forms during this time
Precambrian Eon continued….
Earth originally thought to be
“dead”
Volcanoes produce toxic
atmosphere
Water and water Vapor that form
the oceans comes from volcanoes,
asteroids and comets!!!
*Precambrian Eon continued….*
Closer look at rocks show Signs of
cynobacteria
Cynobacteria-changed Earth’s past
atmosphere of water vapor, ammonia
and methane into Nitrogen and
Oxygen: STILL FOUND ALIVE
TODAY in deep sea Thermal Vents and
in volcanoes
Today’s atmosphere made up of
nitrogen , oxygen and water vapor
Phanerozoic Eon (3 Eras)
*Paleozoic
Era: 545-245m.y.a.:
Basic Traits*
The longest of all the Eras on the
Earth
Contains 7 periods
Fossils of large organisms first found
in this era
Almost all are marine environment
Largest land Continent called
Gondwana (begins with 90 % of
Earth’s surface covered by water)
Warm Earth; Life limited to oceans;
ozone layer not fully developed: no
plants on land intially
Ends with the largest mass extinction
in Earth’s history (90% of all life
killed)
*Why did life first start in the
ocean?*
More stable environment:
Water 22x heat capacity
than air
UV Protection:
– DNA Damaged by UV
radiation
– DNA contains all
information for life
– Earth’s ozone layer just
starting to develop from
oxygen produced by
cynobacteria
*Why did life first start in the
ocean?*
Gravity’s affect
neutralized
-organisms would
develop in
environment in which
gravity would have no
impact on animal’s
structure
– NO need for powerful
muscles to move
*Why did life first start in the
ocean?*
Easier to obtain
minerals and gases
necessary for life
Water naturally has
these items dissolved
in it
Organisms could just
absorb materials as
water passed by
*Easier to obtain food*
Food would be
suspended in 3
dimensions: filter
feeding or feeding
with tentacles become
popular
7 periods of Paleozoic Era
Cambrian Period (545-
505)
– Trilobites
– Clams
– Inland seas suggest
warm Earth
– Land Formation:
supercontinent
Gondwana; (S
hemisphere)
Ordovician Period (505-438)
First land plants (ferns)
First vertebrates: early fish
appear
Life moves into shallower
water: Suggests ozone
layer almost fully
developed as life moves
closer to land
Laurussia seperates from
Gondwana
Silurian Period (438-408)
Corals Dominate World’s
Oceans
Warm Earth
Plants move further inland
Animals now moving
further inland by way of
water; fresh water fish
N. America covered by
shallow sea
*Devonian Period (408-360)*
Fish dominate oceans
First amphibians
Signs of Earth
beginning to cool:
Water retreats forcing
organisms to adapt to
the new changes.
More land created
Mississippian Period (360-320)
Amphibians dominate
land life
Earth much cooler as
glaciers move
southward from polar
regions
Cooler Earth forces
Amphibians to adapt
to changes; (less
water-thicker skin)
Pennsylvanian Period (320-286)
First reptiles
and insects
Shallow seas
over N.America
almost
disappeared
Cooler Earth
*Permian Period (286-245)*
Glaciers retreat
Earth Warming back up
Ends with largest mass extinction in fossil
record (Asteroid impact)
*Mesozoic Era *
AGE OF DINOSAURS
245-65 Million Years Ago
Split into 3 major periods
Triassic period (245-208 million years)
Jurassic Period (208-144 million years)
Cretaceous Period (144-65 million years)
Triassic Period
Marks beginning of Mesozoic Era
First dinosaurs and mammals appeared
around 225 million years ago
Atlantic Ocean
Pangaea breaks up
Flowering Plants appear
Eoraptor, Plateosaurus and Teratosaurus
*Why Dinosaurs Evolve*
Environmental Factors- As Pangaea break
apart each land mass gets a unique climate
Disease Influence- Diseases possible reason
species die out
Competition for Food- organisms compete
for same food sources; winners live losers
die
Predatory Influence- animals develop
defenses against Predators
Jurassic Period (208-144)
Flowering Plants and Dinosaurs dominate land
Birds appear
Appalachian Mountains Form
Dinosaurs become more diverse from basic shapes
Allosaurus
Stegosaurus
Diplodicus
Ceratosaurus
Cretaceous Period (144-65)
Most advanced dinosaurs: Highly
specialized, most successful of all dinosaur
species
Modern Earth Appears
Ends in Mass Extinction of Dinosaurs
Tyrannosaurs, Tricerotops, Ankylosaurus,
Protocerotype, Velocoraptors, Pterodactyl
*Meteorite Theory?*
Says that asteroid/comet 3-5 miles wide
struck near Yucatan Peninsula and caused
Dinosaur Extinction
Iridium deposits in KT layer help support
this
However, closest Dinosaur bones ever
found date about 1,000 prior to event
Climate Change/Disease reason for
extinction??
*Cenozoic Era*
Continents were drifting apart—present
time of Earth
African plate collided with European plate
creating the Alps
India slammed into Asian plate creating
Himalayas
Climate was cooled causing several “ice
ages”
*Mammals Survive because*
Small size easier to maintain body
temperature in climate change
Ability to Hibernate during an extreme
event
Mothers provide food for young from milk,
No other organisms do this (mammals
unique)
Cenozoic Era
Age of Mammals (65mya- present day)
2 Periods
Tertiary Period (65mya – 1.6mya)
Earth’s climate was warm and mild
Ocean mammals like dolphins and whales
evolve
Land-insects, flowering plants and
mammals, birds dominate
Mega mammals mammals evolve
Alps and Himalayas Form
Quaternary Period: (1.6 mya- today)
Mega mammals die out/ (Climate Change?)
Present period
Humans appear—100,000 years ago
Grand Canyon forms
Last ice age 15,000-10,000 years ago