Paleontology

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Paleontology
PaleontologyThe study of the fossil record.
Fossils are any evidence of plants or animals
that have existed in the past and are now
incorporated into the earths crust.
Paleontology is the most direct evidence of
evolution.
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Fossilization

• Organism dies and is quickly covered by sediment
  (mud, sand, volcanic ash) to exclude oxygen and
  prevent decomposition.
• Dissolved ions infiltrate tissues and replace
  hard parts (or if silica is involved soft parts
  can be replaced).
• Compression by more sediments converts remains
  into a stony replica.
• A model is a fossil of an entire organism, part
  of an organism or its excrement.
• Mold is an impression left by an organism (e.g.,
  a worm burrow).
• A cast is mold that has been filled in and the
  mold is then worn away leaving the cast.
• Rock strata indicate a fossil organisms age.
• Strata result from differing rates of
  sedimentation.
• Upper strata are younger than older strata.
• Fossils in upper strata are, therefore, younger
  than fossils in older strata.

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Evidence of Evolution

• Microevolution--A change in the frequency of
  alleles (genes) in populations over time. This
  form of evolution has been directly observed in
  the laboratory and the field.
• Pesticide and antibiotic resistance.
• Finch evolution on Galapagos Islands.
• Macroevolution--Large-scale changes that result
  in extinction and the formation of new species.
  Sources of evidence are compelling
• Biogeography
• Paleontology
• Homology and Analogy
• Developmental Patterns

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Evidence of Evolution--Biogeography
BiogeographyThe study of the geographic
distribution of plants and animals and the
explanation of why they are distributed as they
are. Examplenative cats of Americas and Africa.
All cats are clearly identifiable as catsan
indication of a common origin. We now know that
cats originated in Europe about 30 million years
ago. They spread throughout the Old World and
into the new world across the Bering land-bridge
about 5 million years ago. The variety that we
see today is the result of adaptations to unique
environments into which they spread.
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Amphibian like fish

• Acanthostega gunnari (Jarvik 1952, 1980) is one
  of a small but increasing number of genera of
  stem-tetrapods known from the Upper Devonian,
  which are providing an expanding view of the
  appearance of tetrapods and the origin of limbs
  with digits (Coates and Clack 1990, Clack and
  Coates 1995, Gould 1991, Pough et al. 1996,
  Thomson 1993, Zimmer 1995). Acanthostega is
  represented by exceptionally well-preserved
  material. Notable features are the well-ossified
  gill arches combined with post-branchial lamina
  of the shoulder girdle, together suggesting
  retention of functional internal gills
  paddle-like limbs with eight digits on each limb
  and a deep tail supported by finrays and
  accessory internal supports (Coates 1996). It
  comes from the Remigolepis Group of the Famennian
  of East Greenland, which date from about 360 mya.

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Amphibian like reptiles

• Seymouria is about 32-inches long. It is the
  "missing link" between amphibians and reptiles.
  It is unknown whether they had scales or slick
  skin. Seymouria was a small land dwelling animal
  that lived about 280 million years ago during the
  Permian Period of the Paleozoic Era and moved
  about by undulating its Seymouria is about
  32-inches long. It is the "missing link" between
  amphibians and reptiles. It is unknown whether
  they had scales or slick skin. Seymouria was a
  small land dwelling animal that lived about 280
  million years ago during the Permian Period of
  the Paleozoic Era and moved about by undulating
  its backbone from side to side. It was probably
  cold-blooded and had a small brain. It is very
  much debated if Seymouria is an amphibian or
  reptile. Many believe it to be a very evolved
  amphibian. Seymouria was probably an omnivore
  that ate insects, small vertebrates and carrion.
  backbone from side to side. It was probably
  cold-blooded and had a small brain. It is very
  much debated if Seymouria is an amphibian or
  reptile. Many believe it to be a very evolved
  amphibian. Seymouria was probably an omnivore
  that ate insects, small vertebrates and carrion.

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Reptile like birds

• It has long been accepted that Archaeopteryx was
  a transitional form between birds and reptiles,
  and that it is the earliest known bird. Lately,
  scientists have realized that it bears even more
  resemblance to its ancestors, the Maniraptora,
  than to modern birds providing a strong
  phylogenetic link between the two groups. It is
  one of the most important fossils ever
  discovered.
• Unlike all living birds, Archaeopteryx had a full
  set of teeth, a rather flat sternum
  ("breastbone"), a long, bony tail, gastralia
  ("belly ribs"), and three claws on the wing which
  could have still been used to grasp prey (or
  maybe trees). However, its feathers, wings,
  furcula ("wishbone") and reduced fingers are all
  characteristics of modern birds.

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Reptile like mammals

• The Theriodonts evolved a feeding mechanism much
  more successful than that of the Dinocephalia.
  The quadrate bone in the jaw was reduced in size.
  When the jaws are widely opened (drawing, above)
  the articular bone (art in the diagram) toghtly
  grips the head of the small quadrate (q). The
  lower incisors pass entirely behind the upper
  incisors when the jaws are closed. The
  development of versatile jaw movements and a more
  precise type of dental occlusion also played a
  critical role in preadapting the elements of the
  theriodont articular complex for becoming the
  ossicles of the mammalian middle ear.

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Homology and Analogy
Comparative AnatomyThe study of the structure of
living and fossil animals in an attempt to
discern evolutionary relationships. HomologyResem
blances of structure based on common ancestry.
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Analogy and Convergent Evolution

• Convergent evolutionResemblances of structure
  that are the result of organisms adapting to
  similar environmental conditions, not a result of
  common ancestry. The wings of birds and insects
  are analogous (not homologous) and evidence of
  organisms evolving in similar environments.

http//www.thenativefloridian.com/eco-tours.htm
http//claw.org/member/cc/cc4/cc46_1.shtml
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Evidence of Evolution

• Vestigial structuresStructures that are now
  apparently useless but once had a function in an
  ancestral animal. Ex., vestigial leg bones of
  boa constrictors.
• Extinction
• Comparative embryologyEmbryological stages often
  retain features that reflect earlier evolutionary
  stages. Ex., pharyngeal (gill) pouches of
  mammalian embryos.

www.kingsnake.com/windingcreek/guyana.html
Cervical Fistula
Kent. 1992. Comparative Anatomy of the
Vertebrates. Mosby
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Co-evolution
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Tempo of Evolution
time
Punctuated Equilibrium
Gradualism
Figure 24.13