Earth

1
Earths History
2
Origin of the Earth

• Nebular Hypothesis
• Bodies of our solar system condensed from an
  enormous cloud
• Cloud began contracting, spinning, and flattening
• Earth
• Density sorted material and eventually, gases
  escaped from the interior to form an atmosphere

3
Earths Atmosphere Evolves

• Outgassing
• Gases that are in molten rock are gradually
  released
• Water vapor condensed to form clouds
• Rain cooled Earths crust until the rains slowly
  filled low areas, forming the oceans
• Reduced CO2 because it became trapped in water
• Plants evolved and released oxygen

4
Precambrian Time

• 4.6 billion to 570 million years ago
• Precambrian Rocks
• Shields
• Areas shaped like shields that have been
  extensively eroded to reveal Precambrian rock
• Mostly deformed metamorphic rock
• Ore deposits

5
Precambrian Time

• Precambrian Fossils
• Stromatolites
• Calcium carbonate deposited by algae
• Indirect evidence of algae
• Tiny organisms
• Life 3.5 billion years ago
• Most preserved in chert, a hard, dense chemical
  sedimentary rock
• Prokaryotes found (blue-green algae bacteria)
• Southern Africa3.1 billion years
• Lake Superior1.7 billion years

6
Precambrian Time

• Eukaryotes found (green algae)
• Bitter Springs, Australia1 billion years
• Plant fossils date from the middle Precambrian
• Trace fossils of animals
• Trails and worm holes
• Fossil impressions
• Animal fossils date from the late Precambrian
• Diverse and multicelled organisms exist by the
  close of the Precambrian

7
Paleozoic EraLife Explodes

• 570-245 million years ago
• Hard parts appeared on organisms
• Early Paleozoic History
• Mountain building affected eastern North
  Americalong since eroded

8
Paleozoic EraLife Explodes

• Early Paleozoic Life Age of Invertebrates
• Restricted to seas
• Cambrian
• Trilobites
• Mud-burrowing scavengers
• More than 600 genera
• Ordovicianshallow seas
• Organisms with hard parts
• Brachiopods
• Adults attached to the sea floor, larvae
  free-swimming
• Cephalopods
• Mobile, highly developed mollusks predators

9
Paleozoic EraLife Explodes

• Late Paleozoic History
• Devonian, Mississippian, Pennsylvanian, and
  Permian periods
• Pangaea
• Extreme seasons that caused one of the most
  dramatic biological declines in history

10
Paleozoic EraLife Explodes

• Late Paleozoic Life
• Land plants developed
• Fishes continued to adapt
• Devonian period Age of Fishes
• Lobe-finned fish evolved into amphibians
• Insects
• Extensive coal swamps develop

11
Paleozoic Extinction

• Climates changed because of the formation of
  Pangaea
• 75 of amphibians disappeared
• Up to 95 of marine life disappeared
• 1 of 5 mass extinctions
• Cause is uncertain

12
Mesozoic EraAge of the Dinosaurs

• 245 to 66 million years ago
• Mesozoic History
• Much of worlds land above sea level
• Breakup of Pangaea
• Mountains of western North America begin forming

13
Mesozoic EraAge of the Dinosaurs

• Mesozoic Life
• Survivors of the great Paleozoic extinction
• Gymnosperms became dominant
• Reptiles adapt to dry climate
• Reptiles have shell-covered eggs that can be laid
  on the land
• One group of reptiles led to the birds
• Many reptile groups and other animal groups
  became extinct at the close of the Mesozoic

14
Cenozoic EraAge of Mammals

• 66 million years ago to present
• North America
• Most was above sea level
• Mountain building, volcanism, and earthquakes in
  the West
• In the East stable with abundant marine
  sedimentation eroded Appalachians were raised by
  isostatic adjustments

15
Cenozoic EraAge of Mammals

• Western North America
• Rivers erode and form gorges (Grand Canyon)
• Volcanic activity common
• Coast ranges form
• Sierra Nevada become fault-block mountains

16
Cenozoic EraAge of Mammals

• Cenozoic life
• Mammals replace reptiles as dominant land animals
• Angiosperms dominate the plant world
• Mammals evolve after the reptilian extinctions of
  the Mesozoic
• Marsupials
• Placentals

17
Cenozoic EraAge of Mammals

• Mammals diversify rapidly and some groups become
  very large
• Hornless rhinocerosnearly 16 feet high
• Many large animals became extinct
• Humans evolve