chapter 22

• What did Darwin discover in the Galápagos Islands?

  Unique plants and animals
• What is the focal point of evolutionary theory?

  Speciation, the origin of new species
• What does microevolution consist of?

  Adaptations within a single population
• What is macroevolution?

  Evolutionary change above the species level
• How does the Biological Species Concept define a species?

  A group that can interbreed and produce fertile offspring
• What prevents populations from becoming different from one another?

  Gene flow between populations of the same species
• What are the steps involved in speciation?

  1. Separation (no gene flow)
  2. Adaptation
  3. Division
• What is reproductive isolation?

  Barriers that impede species from producing offspring
• How can reproductive isolation be classified?

  By factors acting before or after fertilization
• What are prezygotic barriers?

  Barriers that block fertilization from occurring
• What is habitat isolation?

  Species rarely encounter each other due to different habitats
• What is temporal isolation?

  Species breed at different times and cannot mix gametes
• What is behavioral isolation?

  Unique courtship rituals act as barriers
• What is mechanical isolation?

  Morphological differences prevent successful mating
• What is gametic isolation?

  Sperm cannot fertilize eggs of another species
• What are postzygotic barriers?

  Barriers that prevent hybrid zygotes from developing
• What is reduced hybrid viability?

  Hybrid development is impaired by parental genes
• What is reduced hybrid fertility?

  Hybrids may be vigorous but sterile
• What is hybrid breakdown?

  First-generation hybrids are fertile, but later generations are not
• What is a limitation of the Biological Species Concept?

  Cannot be applied to fossils or asexual organisms
• How can gene flow occur between distinct species?

  Through hybridization, like grizzly and polar bears
• What are the two ways speciation can occur?

  • Allopatric speciation
  • Sympatric speciation
• What is allopatric speciation?

  Speciation due to geographic isolation
• What happens during allopatric speciation?

  Gene flow is interrupted when populations are isolated
• What can separate populations in allopatric speciation?

  Geographic barriers or random colonization
• How do separate populations evolve in allopatric speciation?

  Through mutation, natural selection, and genetic drift
• What is evidence of allopatric speciation?

  Regions with barriers have more species
• How does reproductive isolation relate to geographic distance?

  Increases as distance between populations increases
• What was the result of the mating experiments with flies?

  Flies raised on different mediums showed mating preferences
• What is the main concept of allopatric speciation?

  Speciation due to geographic isolation
• Why do regions with many geographic barriers have more species?

  Less gene flow between populations
• What were the results of the mating experiments with different populations of flies?

  • Flies raised on starch and maltose showed no preference
  • Indicates potential for reproductive isolation
• What is the definition of sympatric speciation?

  Speciation in overlapping geographic populations

  
• What factors can reduce gene flow in sympatric speciation?

  Polyploidy, habitat differentiation, sexual selection
• What is polyploidy?

  Presence of extra sets of chromosomes
• How does polyploidy begin?

  With diploid gametes formed during cell division
• What is the result of a 2n gamete combining with an n gamete?

  Forms a 3n zygote, which is sterile
• What is an autopolyploid?

  Individual with more than two chromosome sets from one species
• Why is polyploidy important in plants?

  It allows rapid speciation through breeding
• What is an allopolyploid?

  Species with multiple chromosome sets from different species