Transcript EarthHistory

Earth’s History
The Origins of Life
Evidence suggests that
all life originated in
the oceans.
The first selfsustaining molecules
may have formed deep
below the layers of ice
near hydrothermal
vents.
The Origins of Life
1953 –
Stanley Miller
The Origins of Life
Recent research now suggests that simple
organic compounds were brought to Earth
on comets, meteors, and asteroids which
crashed into the Earth during its birth.
Origins of life – 3 Easy Steps!
1. Make organic molecules (see Miller)
2. Replicate self
3. Metabolism
Minerals from Black Smokers; bacteria chemosynthesize minerals; tube worms eat bacteria
The
geologic
time scale
Precambrian era
4.5 billion to 540 million years ago
88% of Earth's history
Only sketchy knowledge
Most Precambrian rocks are devoid of
fossils
Precambrian era
Precambrian rocks
Most are buried from view
Each continent has a "core area" of
Precambrian rocks called a shield
Extensive iron ore deposits
Absent are fossil fuels
Precambrian shields
Precambrian era
Earth's atmosphere
Primitive atmosphere formed from volcanic
gases
Water vapor condenses and forms primitive
oceans as Earth cools
What caused the change
in the composition of
our atmosphere?
1. “Locking” up of CO2
into rocks (such as
limestones)
2. Development of the first
“plants”
Precambrian era
Earth's atmosphere
Bacteria evolve
Plants evolve and photosynthesis produces
oxygen
Oxygen content in the atmosphere increases
By about 4 billion years after Earth formed,
abundant ocean-dwelling organisms that require
oxygen existed
Precambrian era
Achaean Era
Chemical signs of life
Prokaryotes – single celled organisms with no
membrane around the “nucleus”
Precambrian era
Oldest fossils are
cyanobacteria from
NW Australia and are
3.4 – 3.5 b.y.o
Stromatolites are
colonial structures
formed by
photosynthesizing
cyanobacteria and
other microbes
Modern stromatolites,
Shark’s Bay Australia,
and a 2.2 billion year old
fossil stromatolite from
Michigan
Precambrian era
Proterozoic Era
Eukaryotes – cells with a nucleus and
organelles
Developed after the development of free O2 in
the atmosphere
Precambrian era
Precambrian fossils
Plant fossils date from the middle Precambrian
Animal fossils date from the late Precambrian
Diverse and multicelled organisms exist by the
close of the Precambrian
The
geologic
time scale
Paleozoic era
540 million years ago to about 248 million
years ago
First life forms with hard parts
Abundant Paleozoic fossils
Early Paleozoic history
Southern continent of Gondwanaland exists
Paleozoic era
Early Paleozoic history
North America
• A barren lowland
• Seas move inland and recede several times and
shallow marine basins evaporate leaving rock salt
and gypsum deposits
• Taconic orogeny, a mountain building event, affects
eastern North America
Reconstruction of Earth in
early Paleozoic time
Paleozoic era
Early Paleozoic life
Restricted to seas
Vertebrates had not yet evolved
First organisms with hard parts, such as shells –
perhaps for protection
Paleozoic era
Life consisted of several invertebrate groups
• Trilobites
• Brachiopods
• Cephalopods
tribobite
Waptia fidensis, soft-bodied arthropod
Appearance and relative abundance
of major groups of organisms
Paleozoic era
Late Paleozoic history
Supercontinent of Pangaea forms
Several mountain belts formed during the
movements of the continents
World's climate becomes very seasonal, causing
the dramatic extinction of many species
Formation of Pangaea in
late Paleozoic time
Paleozoic era
Late Paleozoic life
Organisms diversified dramatically
Land plants
Fishes evolve into two groups of bony fish
• Lung fish
• Lobe-finned fish which become the amphibians
Insects invade the land
Amphibians diversify rapidly
Extensive coal swamps develop
Mesozoic era
248 million years ago to about 65 million years
ago
Often called the “age of dinosaurs”
Mesozoic history
Begins with much of the world's land above sea level
Seas invade western North America
Breakup of Pangaea begins forming the Atlantic Ocean
Mesozoic era
Mesozoic history
North American plate began to override the
Pacific plate
Mountains of western North America began
forming
Reconstruction of Earth in
the late Jurassic period
Mesozoic era
Mesozoic life
Survivors of the great Paleozoic extinction
Gymnosperms become the dominant trees
Mesozoic era
Mesozoic life
Reptiles (first true terrestrial animals) readily
adapt to the dry Mesozoic climate
Reptiles have shell-covered eggs that can be
laid on the land
Dinosaurs dominate
Mesozoic era
Mesozoic life
One group of
reptiles led to
the birds
Mesozoic era
Mesozoic life
Many animal groups become extinct at the
close of the Mesozoic
The Chicxulub impact event
Cenozoic era
65 million years ago to the present
Often called the “age of mammals”
Smaller fraction of geologic time than either
the Paleozoic or the Mesozoic
Cenozoic era
North America
Most of the continent was above sea level
throughout the Cenozoic era
Many events of mountain building, volcanism,
and earthquakes in the West
Eastern North America
• Stable with abundant marine sedimentation
• Eroded Appalachians were raised by isostatic
adjustments
Cenozoic era
North America
Western North America
• Building of the Rocky Mountains was coming to an
end
• Large region is uplifted
 Basin and Range Province formed
 Re-elevates the Rockies
 Rivers erode and form gorges (e.g., Grand Canyon and
Black Canyon)
Cenozoic era
North America
Western North America
• Volcanic activity is common
 Fissure eruptions form the Columbia Plateau
 Volcanoes form from northern California to the Canadian
border
• Coast Ranges form
• Sierra Nevada become fault block mountains
• Development of the San Andreas Fault (35 mya)
Formation of the San Andreas
Fault Zone
Cenozoic era
Cenozoic life
Angiosperms (flowering plants with covered
seeds) dominate the plant world
• Strongly influenced the evolution of both birds and
mammals
• Food source for both birds and mammals
Cenozoic era
Cenozoic life
Mammals replace reptiles as the dominant land
animals
Two groups of mammals evolve after the
reptilian extinctions at the close of the
Mesozoic
• Marsupials
• Placentals
Cenozoic era
Cenozoic life
Mammals diversify quite rapidly and some
groups become very large
• e.g., Hornless rhinoceros, which stood nearly 16 feet
high
• Many large animals became extinct
Humans evolve