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The History of Life

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THE HISTORY OF LIFE Ch 14 EARTH S EARLY HISTORY Evolution is a scientific THEORY based on different types of evidence collected over the years Evidence Includes ... – PowerPoint PPT presentation

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Title: The History of Life


1
The History of Life
  • Ch 14

2
Earths Early History
  • Evolution is a scientific THEORY based on
    different types of evidence collected over the
    years
  • Evidence Includes
  • Earth was an inhospitable planet
  • Hot
  • Volcanic gasses
  • First organisms appeared between 3.5 to 3.9
    billion years ago
  • There is direct evidence of Earths history
  • Fossils rocks show that Earth formed about 3.9
    billion years ago

3
History in Rocks
  • Fossils any evidence of an organism that lived
    long ago
  • Trace fossils something left by an animal
    (example footprint, trail, burrow)
  • Casts minerals in rocks fill a space left by a
    decayed organism (form a replica of organism)
  • Petrified fossils minerals replace the hard
    parts of an organism
  • Imprints thin objects can leave an imprint as
    sediments turn to rocks
  • Amber-preserved frozen actual organism is
    trapped in amber or ice

4
Dunkleosteus (30 ft long bony skull shown here
is about 1 meter high) Extinct at the end of the
Devonian
5
Fossil examples
6
Studying fossils
  • Paleontologists study fossils
  • Kinds of organisms that lived
  • Learn about behavior
  • Earths climate
  • Geography (rivers, continent position)
  • Fossils are found in sedimentary rock
  • Organism is buried in mud, sand, or clay soon
    after death
  • Particles compress harden over time to form
    sedimentary rock

7
Determining Fossil Age
  • Relative dating
  • Surface layers are newest so they have the most
    recent fossils.
  • Deeper layers contain older fossils
  • Scientists can determine the order of appearance
    extinction
  • Radiometric dating
  • Uses radioactive isotopes
  • Potassium 40 (half life of 1.3 billion yrs)
  • Carbon 14 (half life of 5730 years)
  • Scientists can approximate ages

8
The Geologic Time Scale
  • A time scale of Earths existence based on fossil
    evidence
  • 4.6 billion years ago present
  • Divided into Eras
  • Precambrian, Paleozoic, Mesozoic, Cenozoic
  • Distinguished by organisms that lived during the
    era
  • Eras are divided into periods
  • Mass extinction entire groups of organisms
    disappear from the fossil record almost all at
    once

9
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10
Precambrian Era
  • 87 of Earths history
  • 3.5 billion years ago to 544 million years ago
  • Began with prokaryotes
  • Eukaryotes developed and flourished
  • Soft-bodied invertebrates (jellyfish, sponges)
  • Oldest fossils 3.5 billion years old
  • resemble forms of modern species of cyanobacteria
  • Stromatolites evidence of photosynthetic
    bacteria

11
Paleozoic Era
  • Beginning (Cambrian period)
  • Dramatic increase in diversity of life forms
  • Worms, sea stars, trilobites in the oceans
  • Fish appeared oldest animals with backbones
  • Land species ferns seed plants
  • Middle amphibians
  • End Reptiles
  • Largest mass extinction 90 of Earths marine
    species 70 of the land species disappeared

12
Mesozoic Era
  • Began about 245 million yrs ago
  • Triassic
  • Mammals appeared on Earth
  • Early mammals were small and mouse-like
  • Jurassic (began 280 million years ago)
  • Age of the Dinosaurs
  • Birds appeared
  • Evidence of bird relation to dinosaurs
  • Cretaceous (began 144 million years ago)
  • New types of mammals flowering plants
  • Mass extinction of dinosaurs 66 million years
    ago

13
Geological Events of the Mesozoic
  • Geologic evidence of a large crater East of
    Mexico
  • Could have filled the atmosphere with dust,
    changing climate
  • Continental Drift
  • Pangaea broke apart continents began to move
    apart
  • Plate tectonics Earths crust consists of
    several rigid plates on top of molten rock.
  • Plates continuously move
  • Explains continental drift

14
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15
Cenozoic Era
  • Began 66 million years ago the current era
  • Mammals began to flourish
  • Primates appeared (30 million years ago)
  • Modern humans appeared (200,000 yrs ago)

16
14.2 Origin of Life
17
The Origin of Life on Earth
  • Abiogenesis life from non-living things and
    Spontaneous Generation idea that nonliving
    material can produce life
  • Disproven by Redi and Pasteur
  • Primordial Soup natural processes formed early
    organic compounds
  • Miller-Urey experiment
  • Biogenesis living organisms only come from
    other living organisms

18
Redi Pasteur
19
The Origin of Cells
  • Prokaryotes Archaebacteria (1st cells)
  • Eukaryotes endosymbiont hypothesis
  • Separate DNA in chloroplasts and mitochondria
  • Both organelles the same size and shape of
    bacteria
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