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Paleontology

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Title: Paleontology


1
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.
2
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

11
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.
12
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.

13
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.

14
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.

15
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.

16
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.
17
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
18
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
19
Co-evolution
20
Tempo of Evolution
time
Punctuated Equilibrium
Gradualism
Figure 24.13
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