The Evolution of Living Things

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Chapter 7

• The Evolution of Living Things

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Diatryma and the Rooster

• Diatryma weighed about 400 pounds (182 kg.)
• Flightless
• Cenozoic Era (57-35) million years ago
• Over 6 feet tall
• Enormous Beak
• Sharp Claws
• Distant relative of the chicken

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Frog Crazy
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Adaptation

• Adaptation a characteristic that helps an
  organism survive and reproduce in its environment
• Adaptations Include Structures and Behaviors
  for
• 1) finding food
• 2) protection
• 3) moving from place to place

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Species

• Species a group of organisms that can mate with
  one another to produce fertile offspring

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Do Species Change over Time?

• Millions of different species occupy the Earth,
  ranging from bacteria to fungi to plants and
  animals.
• Have these same species always existed on Earth?

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The Earth is 4.6 Billion Years Old

• Over that period of time the Earth has changed
  dramatically.

Human existence is less than a hairs width at the
end of the diagram
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How do we estimate the age of the Earth?

• Radioactive Decay of Earths Rocks
• Moon Rocks
• Meteorites

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• Radiometric Dating of Earths Rocks- The ages
  of Earth rocks are measured by the decay of
  long-lived radioactive isotopes of elements that
  occur naturally in rocks and minerals and that
  decay with half lives of 700 million to more than
  100 billion years to stable isotopes of other
  elements. Used to measure the last time that the
  rock being dated was melted.

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Moon Dating

• The Moon is a more primitive planet than Earth
  because it has not been disturbed by plate
  tectonics thus, some of its more ancient rocks
  are more plentiful. Only a small number of rocks
  were returned to Earth by the six Apollo and
  three Luna missions. These rocks vary greatly in
  age, a reflection of their different ages of
  formation and their subsequent histories. The
  oldest dated moon rocks, however, have ages
  between 4.4 and 4.5 billion years and provide a
  minimum age for the formation of our nearest
  planetary neighbor.

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Meteorite Dating

• Thousands of meteorites, which are fragments of
  asteroids that fall to Earth, have been
  recovered. These primitive objects provide the
  best ages for the time of formation of the Solar
  System. There are more than 70 meteorites, of
  different types, whose ages have been measured
  using radiometric dating techniques. The results
  show that the meteorites, and therefore the Solar
  System, formed between 4.53 and 4.58 billion
  years ago.
• The best age for the Earth comes not from dating
  individual rocks but by considering the Earth and
  meteorites as part of the same evolving system

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Evidence for an old universe Absence of short
lived stars from star clusters 14-18 Ga1 Length
it takes light to get to the earth from the most
distant objects in the universe (10 Ga)2 Hubble
expansion of the universe 7 - 20 Ga1
Evidence for an old solar system Age of
meteorites 4.4-4.6 Ga (isochron method)1 Age of
moon 4.5 Ga (radiometric)1 Earth-meteorite
system 4.54 Ga (lead isotope age)1 Evidence for
an old earth Earths oldest rocks 3.8-3.9 Ga
(radiometric)1
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Evolution

• Evolution the process by which populations
  accumulate inherited changes over time.
• Because of evolution scientists think that all
  living things and once living things, from
  daisies to crocodiles to humans share a common
  ancestor.

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The Evidence for Evolution

• Comparative Anatomy comparing similar
  structures in different organisms.
• Fossils the solidified remains or imprints of
  once living organisms.
• Embryonic Anatomy
• Vestigial Structures
• The fossil record provides a historical sequence
  of evolution and life.

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Fossilization

• Paleontology - the study of the past through the
  study of fossils.
• The fossil is a rock - Often the remains of
  preserved organisms are not of the organism
  itself but instead of minerals deposited where,
  especially, hard parts of the organism previously
  existed.

Soft parts tend not to fossilize because they
usually decay prior to mineralization. However,
soft parts, under the right conditions, can also
make impressions. Included among such imprints
are those made during the act of locomotion such
as fossil foot prints or various invertebrate
trails
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The organism is quickly covered in sediment
A once living organism
The organism dies
The soft parts decay
The hard parts make a mold (hollow
impression) which is replaced by minerals
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• There are six ways that organisms can turn into
  fossils, including
• 1) unaltered preservation (like insects or plant
  parts trapped in amber, a hardened form of tree
  sap)
• 2) permineralizationpetrification (in which
  rock-like minerals seep in slowly and replace the
  original organic tissues, forming a rock-like
  fossil - can preserve hard and soft parts - most
  bone and wood fossils are permineralized)
• 3) replacement (An organism's hard parts dissolve
  and are replaced by other minerals.
• 4) carbonizationcoalification
• 5) recrystalization
• 6) authigenic preservation

Most animals did not fossilize they simply
decayed and were lost from the fossil record.
Paleontologists estimate that only a small
percentage of the dinosaur genera that ever lived
have been or will be found as fossils.
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Ways of Dating Fossils

• Relative Dating
• Direct Dating

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• Relative dating
• Uses sediment
• positional information
• the relative positions
• of layers of sediment
• determine the age of the
• fossils found within them.
• Crucial assumptions
• older layers are buried beneath younger layers
  (unless the rock itself has been flipped by
  geologic forces)
• fossils are found within the layer that formed
  contemporaneously with the death of the
  fossilized organism (an assumption which is
  obviously not necessarily true for organisms
  which tend to burrow in sediment)

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Direct dating

• Radioisotope clocks
• Carbon 14 dating
• Non-radioisotope methods of direct dating
• Other methods of direct dating include
• tree ring comparisons
• magnetic alignment with the earth's magnetic pole
  (which tends to switch from North to South from
  time to time known as paleomagnitism)

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