Phylogeny and Systematics

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Phylogeny and Systematics

• Chapter 25
• When biologists study macroevolution, they
  consider the major events revealed by the fossil
  record large diversifications of taxonomic
  groups, the origin of novel biological designs,
  and major extinctions. Phylogeny is the
  evolutionary history of a species. The study of
  the diversity of life and its phylogenetic
  history is called systematics.

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The Fossil Record and Geologic Time

• Phylogeny the evolutionary history of a species
  or group of related species
• Remember ontogeny recapitulates phylogeny
• Systematics study of the biological diversity
  in an evolutionary context
• Fossil record sequence in which fossils appear
  in the layers of sedimentary rock studied by
  paleontologists

http//www.mun.ca/biology/scarr/Phylogeny_of_Repti
les2.gif
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The Fossil Record and Geologic Time

• Sedimentary rock formed from layers of minerals
  settling out of the water
• Dead organisms settle along with the sediments
  and are compacted and sometimes preserved as
  fossils
• Some fossils are impressions the organisms made
  in sediment before they decayed and disappeared
• The fossil record is incomplete because it favors
  organisms that existed for a very long time, were
  relatively widespread, and had shells or hard
  bony skeletons

http//www.students.k.csbsju.edu/krarntson/formati
on_sedimentary1.jpg
(only 1 of organism fossilized)
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Important Fossil Finds

• Australopithecus afarensis Lucy

www.wsu.edu
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Important Fossil Finds

• Coevoltuion organisms that evolved
  simultaneously
• Evidence both from behavior, fossils, and genetics

http//www.wildlifehc.org/ewebeditpro/items/O57F12
76.gif
http//www.middle-fork.org/archives/dUnkBeelikeIns
ect.gif
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The Fossil Record and Geologic Time

• Relative dating fossils in each layer of rock
  represent certain time periods, the layers nearer
  the top representing more recent time periods
• Index fossils those found in more than one
  location that can be used to correlate
  information about the strata in both locations

http//pubs.usgs.gov/gip/geotime/fossils.gif
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The Fossil Record and Geologic Time

• Geologic time scale shows a consistent sequence
  of periods and events in the history of the earth
• Four eras
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic

• (end of each era signifies an extinction)

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The Fossil Record and Geologic Time

• Absolute dating refer to a fossils age given
  in years rather than in reference to one another
• Radiometric dating measuring the level of
  certain radioactive isotopes in fossils or rocks
  to determine their ages

http//www.bible.ca/tracks/dating-radiometric-cart
oon.gif
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The Fossil Record and Geologic Time

• Half-life the length of time it takes for 50
  of the original isotope sample to decay
• Paleontologists measure the amount of an isotope
  in a rock or fossil and then knowing the
  isotopes half-life use that measurement to
  determine the approximate age of the rock

http//www.winona.msus.edu/Geology/MRW/mrwimages/E
arth20History/dating_ig_rx.jpg
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The Fossil Record and Geologic Time

• Continents plates of the earths crust that
  float slowly on the liquid mantle of the earth
• Pangaea about 250 million years ago all major
  land masses were joined in this supercontinent
• The supercontinent broke up about 180 million
  years ago causing extensive geographic isolation

http//www.meckcom.net/ssutphin/pangaea.jpg
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The Fossil Record and Geologic Time

• Extinction can occur because the habitat of a
  species is destroyed or because the environment
  has changed to make existence impossible
• There have been two major extinctions in earths
  history
• Permian extinction
• Cretaceous extinction

http//www.geo.utexas.edu/courses/303/0701_mass_ex
tinctions.jpg
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Mass Extinction

• Mass extinction followed by huge adaptive
  radiations (many natural selections/huge
  diversity of organisms)

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Systematics Connecting Classification to
Phylogeny

• Systematics - study of biological diversity in
  the context of evolution, and it includes
  taxonomy, which is the naming and classification
  of species and groups of species

http//sonne.prz.tu-berlin.de/yomag/upload/11/1/63
19_1_biodiversity-2-large.jpg
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Systematics Connecting Classification to
Phylogeny

• Binomial used to describe species consisting of
  the genus and the species within the genus
• The heirarchical classification of organisms
  consists of the following levels in order of
  increasing broadness species, genus, family,
  order, class, phyla, kingdom, domain

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Systematics Connecting Classification to
Phylogeny

• Phylogenetic trees show the heirarchical
  classification of taxonomic levels for organisms
• Cladogram relational diagrams based on
  phylogeny, each branch is called a clade and the
  sequence of branches is based on homology
• The greater the homology between two organisms
  the more closely related they are evolutionarily
  through common ancestry

http//www.calacademy.org/research/izg/CLADOGRAMS
20FOR20WEB/cladogram20Animals.jpg
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Systematics Connecting Classification to
Phylogeny

• Convergent evolution takes place when two
  organisms became alike because they adapted to
  similar environmental challenges, not because
  they have evolved form a common ancestor, this is
  known as analogy

http//www.pbs.org/wgbh/evolution/library/01/4/ima
ges/l_014_01_l.jpg
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Convergent vs Divergent Evolution

• Analogous vs Homologous Adaptations

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Convergent vs Divergent Evolution

• Homologous Adaptations
• Cladogram
• Similarities explained through shared ancestry
• Analogous adaptations
• No cladogram for trait
• Similarities explained through similar
  environments, natural selection occurred
  separately and similarity

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Systematics Connecting Classification to
Phylogeny

• Molecular systematics the comparison of genes
  and proteins of different organisms allows us to
  determine evolutionary relationships on a
  molecular level
• The more alike the DNA sequences of two organisms
  are, the more closely related they are
  evolutionarily

http//www.zin.ru/labs/img/molsyst_01.jpg
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Systematics Connecting Classification to
Phylogeny

• The rate of evolution of DNA sequences varies
  from one part of the genome to another, so
  comparing these different sequences helps us to
  investigate relationships between groups of
  organisms that diverged a long time ago

http//www.life.umd.edu/classroom/biol106h/Lec8/5p
roteins.jpg
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Systematics Connecting Classification to
Phylogeny

• Parsimony principle that dictates that theories
  should be kept as simple as possible while still
  being consistent with the evidence
• This way of thinking is used to create phylogenies

http//www.fiu.edu/biology/pcb4674/ch14/PARSIMONY
.JPEG
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Systematics Connecting Classification to
Phylogeny

• Parsimony can be applied to the creation of
  phylogenetic trees because in evolution heredity
  fidelity is more common than change - in other
  words, phylogenetic trees are hypothetical
• Molecular clocks methods used to place the
  origin of taxonomic groups more precisely in time

http//upload.wikimedia.org/wikipedia/en/e/e7/Phyl
ogeneticTree.jpg
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AP Themes

• Science as a process new evidence has created
  the 3 domain system instead of five kingdoms
• Continuity and Change- all species tend to
  maintain themselves from generation to generation
  (pass on your genes) but some change occurs in
  DNA over time
• Structure and Function homologous digits have
  different functions now in descendents
• Interdependence on nature we are dependent on
  environment, including what adaptations our
  species develops
• Evolution explains our diverse species
• Science, Technology, and Society Current
  research is locating genes for traits and our
  phylogenetic tree