MACROEVOLUTION & FOSSIL RECORD 2

Nota:

• referring to evolution of everything - earth appear ~4.5 billions ago

1. Precambrian
   1. origin of the earth - 1st fossil prokaryotes - photosynthesis - 1st eukaryotic cells - 1st multicellular organism (Ediacaran)
   2. earliest known metazoan (620-550 mya) --> Ediacaran Fauna

      Nota:

      • - sponges, jellyfish, comb jellies
2. Paleozoic
   1. Cambrian
      1. Cambrian Explosion
   2. Ordovician
      1. Jawless fish, vascular plant, Land Arthropods
   3. Silurian
   4. Devonian
      1. Bony fishes, Amphibians, Insects
   5. Carboniferous
      1. Reptiles, True ferns, first seed plants
   6. Permian
      1. Beetles
3. Mesozoic
   1. Triassic
   2. Jurassic
   3. Cretaceous
4. Cenozoic
   1. Tertiary
      1. Paleogene
      2. Geogene
   2. Quarternary
      1. Mass extinction?
5. Cambrian Explosion
   1. - sudden appearance & diversification of most major grps of complex animals
   2. The Burgess Shale

      Nota:

      • soft bodies animal are well preserved
   3. why?
      1. Increase in O2
      2. evo of eyes
      3. Non-sessile fauna - fill available niches
      4. predator-prey arms race
      5. Extinction

1. 1) End Ordivician

   Nota:

   • 60% marine invertebrate genera go extinct
   1. 3rd largest, 440 mya, 22% families and ~60% genera extinct, CO2 decrease, huge ice caps, sea level fell
2. 2) Late Devonian

   Nota:

   • 57%
3. 3) End Permian

   Nota:

   • 82%
   1. Biggest, 250 mya, 57% families, 82% genera.
   2. suggested cause: formation of Pangea, anoxic ocean

      Nota:

      • most affected : animals w carbonate skeleton, weak circulation and low metabolic rate (e.g. corals, brachiopods) vice versa less affected: + gills, (mollusks, arthropods, chordates)
4. 4) End Triassic

   Nota:

   • 53%
5. 5) End Cretaceous

   Nota:

   • 47%
   1. K-T extinction
   2. losses not evenly distributed among taxa
      1. suggested that those sp - move to new habitat, or hibernate, or dormant
   3. Chicxulub crater found - impact site
      1. massive gravitational & magnetic anomalies
      2. found shock quartz- microtectites

         Nota:

         • only found on asteroid hit
      3. Iridium layer (spike) - abundant in asteroid
         1. the extinction event is related to the huge asteroid hit

1. extinction occur continually
2. 96% extinction occur in background time
3. variation rates
4. Mass extinction happens at global scale
5. 5-50 billion ever lived, but only 5-50 mil only alive

1. Extinction creates OPPORTUNITY
   1. Extinction event at the end of Proterozoic - removed a large part of Ediacaran Fauna - allow for new opportunity and morphological innovation
      1. ADAPTIVE RADIATION
         1. occurs when a single or small group of ancestral sp rapidly diversifies into a large # of descendants that occupy a wide variety of ecological niches.

            Nota:

            • e.g. Galapagos Finches e.g. Mammal radiation (only 2 lineages were present 65MYBP) -present day, 20 orders available
2. Modes of diversification
   1. STASIS
      1. describes sp that appear and persist for millions of years without any change
   2. PHYLETIC GRADUALISM (Darwin)
      1. def : the gradual nature of evolution by natural selection
      2. suggested that sudden appearance of new taxa wa due to the incompleteness of fossil record
   3. PUNCTUATED EQM (Niles Eldredge & Stephen Jay Gould)
      1. claimed that stasis was a real pattern
      2. suggested that morphological change occur during speciation
   4. Morphological and genetic variation are not necessarily coupled (e.g. horseshoe crab)
   5. KEY
      1. 1) most differences amongst higher taxa occur after successive fixation of small phenotypic changes
      2. 2) Functional consideration - large changes need to accompanied by other large changes (mutations) to ensure survival