Ch 16: Large Scale Evolution

• Allopatric Speciation


  Geographic isolation of populations
• Sympatric Speciation


  A population develops into two or more reproductively isolated groups without prior geographic isolation
• Reproductive Barriers


  Isolating mechanisms that prevent successful reproduction
• 2 types of reproductive barriers

  Prezygotic: Prevent fertilization from taking place

  Postzygotic: Reduces viability/fertility
• Types of Prezygotic Isolation Mechanisms

  1. Habitat: Two species live in 2 different areas so it's harder to meet & attempt to reproduce
  2. Temporal: Two species live in the same area, but reproduces at different times
  3. Behavioral: Many animal species have courtship patterns
  4. Mechanical: An animal's genitalia or plant floral structures aren't compatibly preventing reproduction
  5. Gamete: Gamete don't fuse
• Types of Post Zygotic Isolating Mechanisms

  1. Zygote mortality: The hybrid zygote dies
  2. Hybrid sterility: The hybrid zygote may develop into a sterile adult
  3. F2 fitness: If hybrids can reproduce, their offspring are unable to reproduce
• Adaptive Radiation

  • Involves the evolution of several new species from a common ancestral species
  • Occurs as natural selection drives members of the ancestral species to adapt to different environments
• Prezygotic Isolating Mechanisms

  • Occurs before the formation of a zygote
  • Prevents reproductive attempts
• Postzygotic Isolating Mechanisms

  • Occurs after the formation of a zygote
  • They prevent hybrid offspring from developing or breeding further
• Paleontology


  The study of fossils
• The Geological Timescale


  constructed by studying the fossils in the various rock strata
• The earth's history can be divided into segments:

  1. Epochs: The shortest segments
  2. Period: A series of epochs
  3. Era: Several periods combined
• The Gradualist Model

  • Evolutionary changes occurred gradually
  • Over very long time periods
• Punctuated equilibrium


  The idea that evolution occurs in spurts instead of following the slow, but steady path
• There's is evidence 5 extinction events have taken place, and we are currently in the 6th one.
• Continental drift 


  The gradual movement of continents across earth's surface
• Meteorites and Asteroids impacts are another explanation for mass extinctions taking place
• Scientists have stated that we are currently living through the 6th extinction event and it was caused by humans
• Systematics


  Branch of biology that focus on understanding the evolutionary history of life on earth
• Phylogeny


  The evolutionary history of a group of organisms
• Taxonomy


  The identifying, naming, and classifying organisms
• The goal of Systematics 


  Is to establish the evolutionary history of a group of organisms
• The order of classifying organisms

  1. Domain
  2. Kingdom
  3. Phylum
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species
• Phylogenetic Tree


  a diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor