evolution

• Evolution


  Biological change in populations over time that makes descendants genetically different from their ancestors
• Microevolution


  Small scale evolution affecting a single population
• Macroevolution


  Large scale evolution affecting a species across populations
• Natural selection


  • Mechanism of evolution where organisms with the "best" traits are favored and thus live longer and reproduce more, causing changes in the population over time so that the fittest survive
• Fitness


  A measure of how well an organism can survive in its environment
• Adaptation


  A feature that allows an organism to better survive in its environment
• Gene pool


  The combined alleles of all individuals in a population
• Genetic drift


  Mechanism of evolution that occurs when random change in the allele frequency happens in the population
• Gene flow


  Mechanism of evolution caused by the movement of genes into or out of a population
• Sexual selection


  Mechanism of evolution that favors traits that potentially decrease survival, but increase likelihood of reproduction
• Genetic equilibrium


  When there are no changes in the allele frequencies in a population over time, and thus evolution is not occurring
• Natural selection


  1. Overproduction of offspring leads to competition

  2. Variation within population

  3. Adaptations allow better survival

  4. Traits become more common over time
• The more diverse a species is the less likely the entire species can be eliminated by a sudden event
• Factors contributing to genetic variation


  • Random mutations
  • Genetic recombination during meiosis
  • Migration/gene flow
• Microevolution mechanisms

  1. Genetic drift

  2. Gene flow

  3. Sexual selection
• Conditions for no evolution

  • No mutations
  • No natural selection
  • Large population
  • No migration
  • Random mating
• Species


  Group of organisms that can successfully interbreed and produce viable, fertile offspring
• Adaptive radiation


  A type of divergent evolution occurring on a small scale over a shorter period of time
• Speciation is the forming of a new species while extinction is the elimination of an existing species
• why is isolation important-There has to be some sort of barrier that prevents a subset of a population from reproducing with the rest of the population so that over time, continual reinforcement of only reproducing with each other leads to favoring traits in a small gene pool.  

  •This has to happen enough that the gene pool becomes so different that it can no longer reproduce and create viable offspring with the original population’s gene pool.
• Gradual extinction


  Happens slowly over time
• Mass extinction


  Happens suddenly
• Gradualism


  Slow incremental changes over long periods of time
• Punctuated equilibrium


  Quick bursts of drastic change, followed by periods of genetic stability
• Divergent evolution


  Related species branch off from each other, due to living in different environments
• Convergent evolution


  Unrelated species evolve similar characteristics due to living in similar environments
• Coevolution occurs when two populations of organisms form a specialized relationship that is so close, they evolve in response to each other
• Paleontology


  Study of prehistoric life through the fossil record
• Morphology


  Study of the form of living things
• Biogeography


  Study of the geographic distribution of plants and animals
• Embryology


  Study of embryo development
• Biochemistry


  Study of chemical processes in living things
• Fossils


  Preserved remains of organisms
• Endemic species


  Species that exist only in one geographic region
• Pseudogenes


  Nonfunctional genes
• Transitional fossils play a key role in helping us piece together evolutionary history, specifically by connecting extinct to current species
• Homologous structures


  Same form due to common ancestry, but different function due to living in different environments
• Analogous structures


  Same function due to same environment, but different form due to different ancestry
• Vestigial structures


  Useless but potentially leftover from a previous ancestor
• Biogeography matches what we predict happened with continental drift and provides evidence of divergent evolution