ch 13

    Cards (39)

    • Evolution
      A population's allele composition (frequencies) change over time
    • Agents/factors that evolution relies on

      • Mutations (new alleles)
      • Migration (gene flow)
      • Genetic drift
      • Bottleneck and founder effect
      • Natural and sexual selection
    • Microevolution
      Agents of evolution change allele frequencies/phenotypes in populations over shorter time scales (i.e. a few generations)
    • Microevolution
      • Beneficial alleles maintained; unfavorable/harmful alleles eliminated
      • Causes small-scale changes to species (ex. Peppered moths, antibiotic resistance in bacteria, mouse fur phenotype, etc.)
    • Macroevolution
      Genetic and phenotypic changes over long evolutionary time scales (i.e. millions of years) that result in new species and higher taxa
    • Macroevolution
      • If isolated populations evolve (change) enough to where they are no longer able to reproduce, they are considered two separate species
      • Over billions of years, organisms have changed so much from ancestral forms to warrant classification in higher taxa (i.e. Domain, Kingdom, Phylum, etc.)
    • Evidence of evolution

      1. Population separation
      2. Different evolutionary pressures
      3. Phenotypic variation
    • Evidence of evolution

      • Fossil evidence
      • Biogeography
      • Anatomical/morphological comparisons
      • Embryonic development
      • Molecular (DNA/RNA/Protein) comparisons
    • Paleontology
      Study of ancient life from fossil remains
    • Paleontology
      • Provides most of our understanding of the different types of ancient lifeforms on Earth
      • Fossils: physical remains of ancient organisms preserved in layers of rock
      • Transitional fossils: very rare fossils that clearly show anatomical transitions from ancient life forms into more modern forms
    • Transitional fossil

      • Tiktaalik- fossil evidence of transition from fully-aquatic animals to terrestrial tetrapods
    • Sedimentary rocks

      Layered rocks formed from sand/mud sediments
    • Sedimentary rocks

      • Associated with wind and water erosion of rock
      • Sometimes, organisms would be rapidly buried and preserved in the sediments→ fossils
    • Stratification

      Rock layering with surface layers more recently deposited and older and older layers deeper from surface
    • Geologic timescale

      • Life begins (~3.8 bya)
      • Cambrian explosion (~540 mya)
      • Invasion of land (~470 mya)
      • Dinosaurs, ancient mammals, large trees in forests (~250-65mya)
      • Meteor kills dinosaurs leading to rise of mammals (~65mya)
      • Age of humans (~1.8mya-present)
    • Body fossil

      Rapid preservation in ice, dry air, or tree sap
    • Cast fossil

      Minerals in ground water replace the body parts and crystalize into rock in the shape of the organism
    • Mold fossil

      Hard body parts make impression in sediments then degrade leaving behind their shape in the rock
    • The fossil record is incredibly incomplete
    • Reasons the fossil record is incomplete
      • Some never leave a fossil- soft bodied organisms
      • Erosion/movement of continental plates destroys rock layers
      • Fossils may be in hard-to-reach or poorly-studied places
      • Not all organisms lived in appropriate environments
    • Relative dating

      Based on depth fossil found at. (Deeper= older)
    • Absolute dating

      Age of rock layer determined with radiometric analysis (radioisotope half-life analysis)
    • Radioisotopes
      Some unstable isotopes are deemed "radioactive" when the nucleus spontaneously decays into more stable daughter isotopes and ejects high-energy radiation
    • Half-life

      The average time for half of the radioactive atoms to spontaneously decay into the stable product
    • 14C
      Constantly produced in the atmosphere in reaction between cosmic rays and nitrogen, used to date "recently" deceased organisms
    • 14C dating

      • 14C half-life= 5730 years; ~30,000 year dating ability
    • Plate tectonics

      Tectonic plates- solid top layers moving on hot mantle
    • Biogeography
      The study of species distribution
    • We must consider ancient land formations/environmental conditions to better understand modern or ancient species distributions
    • Biogeography
      • Closely-related flightless birds with wide global distribution
      • Wallace's line- clear difference between animals on the Malay archipelago along a particular line
    • Homologous structures
      Anatomical structures that evolved in the common ancestor and passed to all resulting lineages
    • Analogous structures

      Similar structures/traits due to shared selective pressures- NOT from a direct common ancestor
    • Convergent evolution

      When two or more unrelated lineages of organisms evolve analogous structures and attain similar traits
    • Vestigial character

      No apparent function in modern organism, but homologous to functional structures in other organisms
    • Embryonic development

      • Early embryonic stages are very similar among diverse lineages of animals
      • Genetic programs developed in ancient common ancestors dictate early development
      • Species-specific gene expression patterns take over at later stages and determine each species' unique development
    • Molecular clock
      Comparing gene/protein sequences to understand evolutionary change
    • Before speciation occurs, all members of a population make up a single gene pool
    • If we can estimate # of mutations per unit time, comparing # of DNA/protein sequence differences can reveal approximate time since divergence
    • Molecular clock

      • Cytochrome c amino acid sequence differences between human and different eukaryotes reveal less differences between more closely related species (less time to change independently since species diverged)
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