Phylogeny and Systematics

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Phylogeny andSystematics
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Fossil Formations
Sedimentary Rocks Tracks Petrification Preser
ved Amber
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Dating

• Relative Dating Consistent sequence of sediment
  layers.

• Geological Time Scale
• Consistent sequence of historical periods

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• Absolute Dating
• Radiometric Dating measuring certain
  radio-isotopes w/i fossils. Carbon accumulated
  in body over time (C-14), at death, C-14 decays,
  (Half life 5,730 years)
• Uranium-238 Half life of 4.5 billion years,
  occurs in lava. Degrades once solidified.
  (Determines age of rock layers.

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Phylogeny based on Continental Drift
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Pangaea

• End of Paleozoic Era (250 million)
• Eliminated Isolation
• Increased Competition
• Ocean Basin increased, lowered sea level
• Shallow organisms destroyed
• Mesozoic Era (180 Mill)
• Pangaea breaks up, continental drift
• Explains current distribution of organisms
• (Eutherian and Marsupials)

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Mass Extinctions

• Long period of quiescent, brief species turnover
  time.

• Habitat destroyed or environmental changes
• Two Major extinction periods
• Permian(250 mill) ended 90 of marine animals
• many terrestrial life ended, less than 5
  mill yrs.
• Formation of Pangaea,
• Cretaceous(65 mill) destroyed 50 marine,
• plants and terrestrial animals
  (dinosaurs)
• B/W Mesozoic and Cenozoic thin layer of iridium
• rare on earth, found on meteorites.

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Systematics

• Systematics study of biological diversity in
  evolution
• Binomial Nomenclature
• genus
• specific epithet (species)

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Hierarchical Classification
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Phylogenetic Tree
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Clades Cladogram
Series of dichotomous points represents
divergence of species. Clade each evolutionary
branch.

• Convergent Evolution similarity resemble due to
  similar ecosystems
• Similarities called analogy (not homology)
  wings of bats vs.. birds
• Homologous evolutionlikeness due to common
  ancestry

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Shared Characters

• Shared Primitive Characters homology feature
  predating a taxon
• backbones predate the mammalian taxon.
• Shared Derived Characters evolutionary novelty
  unique to a particular clade
• Outgroup Comparison comparison differentiate
  shared characters that are derived from those
  that are primitive.
• Compare against an outgroup organism that is less
  closely related than the others.
• Ingroup is the group we are comparing together.

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Homology present in both In and Out group is
notochord. Ingroup shows shared primitive and
shared derived characters. Turtle-leopard share
a common ancestor more recent than
salamander-turtle-leopard clade. Does not give
time relationships
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Three possible relationship for the four
species. Parsimony states that the simplest
explanation that fits the facts Is more than
likely correct. Occams Razor
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Phylogenetic Trees are Hypothetical
Parsimony vs.. Analogy vs.. Homology 4 chamber
heart is not homologous but analogous. 4 chamber
heart evolved 2x in vertebrate evolution. May
not be the most parsimonious.
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Molecular Clocks

• Some regions of DNA Evolve at constant rates.
• Relative dating using reliable genes that evolve.
• Assumes that DNA changes are due to genetic
  drift, and mostly are neutral.
• HIV Molecular clock Host jump, different
  strains (HIV-1M) evolves rapidly, Look at
  evolution of gene in a patient over time.
• Samples collect 1980s to 90s, rate of change is
  constant.

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Debates

• Lizards, snakes, crocodiles, and birds
• According to Linnaeus and Darwin, how would he
  place their relationship

Lizards-------Crocs--------Snakes-----------------
---Birds
BUT Using fossils, anatomy, molecular
comparisons We see..
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Phylogenetic Fuse
Molecular Data contradicts other
data. Characteristic evolved/originated early in
history but did not proliferate enough to
be seen in fossil records until extinction of
dinosaurs.
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Human Evolution
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9) 25,000 years ago Other Homo species had gone extinct, leaving only modern humans, Homo sapiens, spread throughout the Old World.
3) gt3 mya Australopithecus afarensis (Lucy) lived in Africa.
7) 100,000 years ago Human brains reached more or less the current range of sizes. Early Homo sapiens lived in Africa. At the same time, Homo neanderthalensis and Homo erectus lived in other parts of the Old World.
1) Before 5 mya In Africa, our ancestral lineage and the chimpanzee lineage split.
5) 2 mya The first members of the Homo clade, with their relatively large brains, lived in Africa.
8) 50,000 years ago Human cultures produced cave paintings and body adornment, and constructed elaborate burials. Also, some groups of modern humans extended their range beyond Africa.
2) Before 4 mya The hominid Australopithecus anamensis walked around what is now Kenya on its hind legs.
4) 2.5 mya Some hominids made tools by chipping stones to form a cutting edge. There were perhaps four or more species of hominid living in Africa.
6) 1.5 mya Hand axes were used. Also, hominids had spread out of Africa and into much of Asia and Europe. These hominids included the ancestors of Neanderthals (Homo neanderthalensis) in Europe and Homo erectus in Asia.