A4.1 Evolution and Speciation

• what can lead to the emergence of analogous structures

  divergent evolution from a recent common ancestor
• Outline Linnaeus's morphological concept of species

  Linnaeus's morphological concept of species states a group of organism with (visible) shared traits.
• what determines the size of a species?

  the total amount of DNA
• What occurs during meiosis but not mitosis?

  homologous chromosomes pair up
• Evolution


  The change in heritable characteristics of a population over time
• Evolution is scientifically measured through fossils, selective breeding, comparative anatomy of animals, nucleotide and amino acid sequences
• Darwinian evolution


  • Natural selection to explain why species change over time
  • Evidence from fossils and observation in Galapagos
  • Competition for resources
  • Natural selection to adapt to environment
  • Isolated groups lead to new species
• Lamarckian evolution


  • Proposed that acquired physical changes in an organism's lifetime are passed onto offspring in a single generation
  • Organs used more grow, organs used less shrink
• Molecular phylogeny


  Comparison of DNA, RNA, amino acids in proteins to determine how closely related organisms are
• Artificial selection


  A process in which humans consciously select for or against particular features in organisms
• Artificial selection illustrates the process of natural selection: Promotion of favourable/desirable varieties and the elimination of undesirable ones
• Artificial selection shows significant changes in a short period of time, evidence that similarly significant changes can occur via natural selection
• Homologous structures


  Structures inherited from a common ancestor, may have evolved different functions
• Adaptive radiation


  Usually rapid diversification from a common ancestor
• The pentadactyl limb is an example of adaptive radiation of vertebrates
• Analogous structures


  Do not derive from a common ancestry, have a different structure but similar function
• Convergent evolution


  The process by which unrelated or distantly related organisms evolve similar structures/features because of similar selection pressure
• Speciation


  An event that produces two new species, increases the total number of species on Earth
• Gene pool


  Consists of all the genes and their different alleles, present in an interbreeding population
• Reproductive isolation


  Members of a species are isolated from others such that they can no longer interbreed with them
• Geographic isolation


  A physical barrier like a mountain range, ocean, or river prevents the movement of individuals between populations