Chapter 17 The History of Life

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Chapter 17The History of Life
Fossil imprint
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The Fossil Record

• Provides evidence
• about the history of
• life on Earth.
• It also shows how
• different groups of
• organisms, including
• species, have
• changed over time.

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Relative vs. Absolute Dating
Comparing Relative and Absolute Dating of Fossils
Relative Dating
Absolute Dating
Can determine Is performed by Drawbacks
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Principle of Superposition

• In an undisturbed sequence of sedimentary rocks,
  the oldest rocks are on the bottom with the most
  recent on top.

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How fossils are formed
Water carries small rock particles to lakes and
seas.
Dead organisms are buried by layers of sediment,
which forms new rock.
The preserved remains may later be discovered and
studied.
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Geological Time Scale

• After the Precambrian Time, the time scale is
  divided into eras, which are subdivided into
  periods.

(millions of years ago)
(millions of years ago)
Era
Period
Time
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
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Geological Time Scale

• The major eras are Paleozoic, Mesozoic, and
  Cenozoic.

(millions of years ago)
(millions of years ago)
Era
Period
Time
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
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Geologic Time Scale

• Each period hosts significant evolutionary
  changes to species diversity and extinction.

(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
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Summary of major events (pg. 429-34)
(millions of years ago)
Key Events
Era
Period
Time
Glaciations mammals increased humans Mammals
diversified grasses Aquatic reptiles
diversified flowering plants mass
extinction Dinosaurs diversified
birds Dinosaurs small mammals cone-bearing
plants Reptiles diversified seed plants mass
extinction Reptiles winged insects diversified
coal swamps Fishes diversified land vertebrates
(primitive amphibians) Land plants land animals
(arthropods) Aquatic arthropods mollusks
vertebrates (jawless fishes) Marine invertebrates
diversified most animal phyla evolved Anaerobic,
then photosynthetic prokaryotes eukaryotes, then
multicellular life
Cenozoic Mesozoic Paleozoic Precambrian Ti
me
Quaternary Tertiary Cretaceous Jurassic Triassic P
ermian Carboniferous Devonian Silurian Ordovician
Cambrian
1.8present 651.8 14565 208145 245208 290245
363290 410363 440410 505440 544505 650544
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Hypothesis of early Earth

• Very hot surface from colliding meteorites
• Very hot planet core from radioactive materials
• Volcanoes spewing lava and gases that helped to
  form the early atmosphere

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Hypothesis of early Earth

• About 4.4 billion years ago, Earth might have
  cooled enough for the water in its atmosphere to
  condense.
• This might have led to millions of years of
  rainstorms with lightning, enough rain to fill
  depressions that became Earths oceans.
• The oldest rocks dated are 3.9 million years old.

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Fossils evidence of an organism that lived long
ago that is preserved in Earths rocks

• Paleontologists estimate that about 95 species
  are extinct from lifes origins.
• Climate and ancient geography can be determined
  from fossils.

Types of Fossils
Formation
Fossils Types
A trace fossil is any indirect evidence
A trace fossil is any indirect evidence
Trace fossils
left by an animal and may include a
footprint, a trail, or a burrow.
When minerals in rocks fill a space
Casts
left by a decayed organism, they make
a replica, or cast, of the organism.
A mold forms when an organism is
A mold forms when an organism is
Molds
buried in sediment and then decays,
leaving an empty space.
Petrified/
Petrified-minerals sometimes penetrate
and replace the hard parts of an
Permineralized
organism. Permineralized-void spaces
fossils
in original organism infilled by
minerals.
Amber-
At times, an entire organism was
Preserved or
quickly trapped in ice or tree sap that
frozen fossils
hardened into amber.
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What has been learned from fossils

• several episodes of mass extinction that fall
  between time divisions
• mass extinction an event that occurs when many
  organisms disappear from the fossil record almost
  at once
• The geologic time scale begins with the formation
  of Earth about 4.6 billion years ago.

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Precambrian 87 of history

• Oldest fossils about 3.4 billion years old
  resembling cyanobacteria stromatolites.
• Stromatolites still form today in Australia from
  mats of cyanobacteria.
• The stromatolites are evidence of the existence
  of photosynthetic organisms on Earth during the
  Precambrian.
• Only prokaryotic life found in fossil record

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End of Precambrian 543 MYA

• multicellular eukaryotes, such as sponges and
  jelly-fishes, diversified and filled the oceans

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Paleozoic and Cambrian Period

• Paleozoic Era more animals and plants
• Early fishes, aquatic vertebrates, ferns
• Middle amphibians
• Late reptiles and mass extinction
• Cambrian Period oceans teemed with many types of
  animals, including worms, sea stars, and unusual
  arthropods

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Mesozoic - 248 MYA

• Triassic Period mammals and dinosaurs
• Jurassic Period dinosaurs and birds
• Cretaceous Period more mammals, flowering
  plants, but mass extinction of dinosaurs 65 MYA

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Continental drift

• Earths continents have moved during Earths
  history and are still moving today at a rate of
  about six centimeters per year.
• The theory for how the continents move is called
  plate tectonics.

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Geologic Time Scale video
Click on image to play video.
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Miller-Urey experiment showed one possible way
for inorganic molecules to form organic molecules.
Mixture of gases simulating atmospheres of early
Earth
Spark simulating lightning storms
Cold water cools chamber, causing droplets to form
Condensation chamber
Water vapor
Liquid containing amino acids and other organic
compounds
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How eukaryotic cells evolved

• Lynn Margulis proposed the endosymbiotic theory.

Chloroplast
Plants and plantlike protists
Aerobic bacteria
Ancient Prokaryotes
Photosynthetic bacteria
Nuclear envelope evolving
Mitochondrion
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Primitive Aerobic Eukaryote
Ancient Anaerobic Prokaryote
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Endosymbiotic theory

• Heterotrophic bacteria have plasmids (DNA loop)
  simple ribosomes in their cytoplasm
• Mitochondria have circular DNA bacteria-like
  ribosomes
• SoEukaryotic cells may have engulfed prokaryotic
  cells by mutualism created the first
  mitochondria.

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• Autotrophic bacteria are Cyanobacteria with
  chlorophyll
• So, Eukaryotic cells may have engulfed
  prokaryotic cyanobacteria by mutualism created
  the first chloroplast.

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• Heterotrophic symbiosis symbiont produces ATP,
  host uses ATP, host protects symbiont
• Autotrophic symbiosis symbiont produces sugar,
  host uses sugar, host protects
  symbiont
• Relationships may allow host to live longer
  reproduce more, thus over time creating more
  complex eukaryotic cells

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Evolution of life video
Click on image to play video.
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Macroevolution

• Large-scale evolutionary patterns and processes
  that occur over long periods of time.
• Includes 6 topics
• Extinction
• Adaptive radiation
• Convergent evolution
• Divergent evolution
• Punctuated equilibrium
• Changes in developmental genes

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Patterns of evolution

• Darwin believed that organisms evolved gradually.
• Niles Eldredge and Stephen Jay Gould believed
  punctuated equilibrium is how organisms evolved,
  periods of rapid evolution followed by periods of
  stasis.

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Adaptive Radiation

• Single species or small groups of species evolved
  into diverse forms living in different ways.

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Convergent Evolution

• Adaptive radiation can produce unrelated
  organisms that look similar due to similar
  environments.

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Coevolution

• Example This butterfly acquires a cardiac
  glycoside from members of the genus Asclepias.
  Because of their milky sap, these are commonly
  referred to as milkweed plants. The plants
  produce this toxin as a defense against
  herbivory, but the Monarch has the ability to
  sequester the toxin in fatty tissues so that it
  makes the butterfly unpalatable while not
  poisoning the butterfly.

The process by which two species evolve in
response to changes in each, other over time.
http//ecology.botany.ufl.edu/ ecologyf02
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