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6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
6a macroevolution
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6a macroevolution


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  • 1. Lecture 6a: Macroevolution Macroevolution
  • 2. Macroevolution
    • Not really different than microevolution, but over a much larger scale
    • Changes to species, not changes to populations
  • 3. Species- what are they anyway?
    • Biolgical Species Concept : members of the same species interbreed and have a shared gene pool, but are reproductively isolated from every other species
    • Speciation : the evolution of new species
  • 4. Species
    • Two animals of the same species can reproduce and have fertile offspring
    • One species can consist of one or many populations
    • Appearance does not necessarily allow you to tell two species apart
  • 5. Reproductive Barriers
    • As speciation occurs, reproductive barriers arise that prevent breeding from occurring between the different species
    • Barriers fall into two categories: prezygotic and postzygotic
  • 6. Prezygotic Barriers
    • Habitat Isolation: The different species inhabit different habitats
    • Temporal Isolation: Breeding season is at different times of the year
    • Behavioral Isolation: Pheromones, courtship rituals, songs or calls, etc are different
    • Mechanical Isolation: Genitalia are incompatible
    • Gamete Isolation: The gametes can not fuse to form a zygote
  • 7. Postzygotic Barriers
    • Zygote mortality: A zygote is formed, but it does not survive
    • Hybrid sterility: The zygote develops into an adult, but it is sterile
    • F2 Fitness: The hybrids can reproduce, but the F2 generation can not
  • 8. Types of Speciation
    • Allopatric Speciation
      • Occurs when populations become geographically isolated, and move further and further apart genetically from the original species
      • Ex. Ensatina salamanders, iguanas
  • 9. Types of Speciation
    • Sympatric speciation
      • Population develops into two or more groups without geographic isolation
      • Polyploidy: increase in number of chromosomes to 3n or higher due to hybridization, sometimes followed by doubling of chromosomes- results in 3rd species
  • 10. Types of Speciation
    • Adaptive Radiation
      • New species evolve from one ancestral species to fill different niches in the habitat
      • Ex. Galapagos finches, Hawaiian honeycreepers
  • 11. Fossils
    • To study extinct species, especially ones from millions of years ago, we look to fossils:
      • The remains or traces of past life
      • Can take several forms- amber, footprints, petrification, actual remains
  • 12. Geologic Time
    • See timeline
    • Cambrian explosion: all major groups of animals appeared
    • Number of species on Earth has continued to increase over time, even to the present day
  • 13.  
  • 14. Speciation
    • We do not know how quickly species arise- there are two models:
      • Gradualistic Model- slow steady change over a long period of time
      • Punctuated Equilibrium: somewhat ‘sudden’ appearance of new species in fossil record
        • The transitional fossils are unlikely due to geographic isolation and small numbers
  • 15. Mass Extinctions
    • Relatively sudden disappearances of large numbers of species
    • Have been several, of course dinos the best known example
    • Two main causes: Continental drift and meteorite impacts
  • 16. Continental Drift
    • The continents on Earth are moving
    • Plate tectonics: The crust of Earth is floating on the molten mantle, the crust is in several pieces
    • As the continents move, the climate changes
  • 17. Pangaea: its formation 250 mya was probably the cause of the Permian Extinction
  • 18. Meteorites
    • Probably the cause of the dinosaur’s extinction
      • Caused massive cloud of dust that blocked the sun, lowering temperatures worldwide
      • Soot and iridium are found in Cretaceous clay, and a crater has been identified as well
  • 19. Systematics
    • As the category gets higher and higher, it gets more and more inclusive
    • Ideally, organisms are classified according to their evolutionary relationships, so taxonomy is in constant flux as we learn more and more
  • 20. Phylogenetic Trees
    • Trees that show relatedness of different organisms
      • Indicate common ancestor, and lines of descent
      • Determined using comparative anatomy, embryology, molecular evidence
  • 21. Anatomy
    • Remember, it matters where the characteristic in question arose from, not what it does now
      • Ex. Thorny devils vs. horny toads have Analagous structures
      • Ex. Vertebrate forelimbs are Homologous structures
  • 22. Using DNA to determine relationships
    • Remember: evolution occurs when mutations in DNA occur-- it can not occur without those random changes
      • Therefore, the more closely related animals are, the fewer differences there will be in their DNA
      • This allows new information about DNA to be included in our understanding of how life on Earth evolved
  • 23.