Bio II

• Macroevolution


  All of the large, complex changes in life's panorama; span very long periods
• Microevolution


  Happen so rapidly; can be observed over just a few years
• Species


  Distinct types of organisms
• Organisms are not truly divided into discrete units called species
• Biologists compare not only the morphology (body form) of different groups of organisms but also their physiology, biochemistry and DNA sequences
• Carolus Linnaeus


  Swedish botanist; defined species as "all examples of creatures that were alike in minute detail of body structure"
• Linnaeus' classifications organized life's diversity but did not consider the role of evolutionary relationships
• Charles Darwin connected species diversity to evolution; said that classifications would come to resemble genealogies or extended "family trees"
• Biological species concept


  A species is a population, or a group of populations, whose members can interbreed and produce fertile offspring
• Speciation


  The formation of new species; occurs when some members of a population can no longer successfully interbreed with the rest of the group
• Difficulties with the biological species concept

  • Cannot apply to asexually producing organism
  • Impossible to apply to extinct organisms
  • Some types of organisms have the potential to interbreed in captivity, but they do not so in nature
  • Reproductive isolation is not always absolute
• How new species can form

  1. A new species can form if a population somehow becomes divided

  2. An intact, interbreeding population shares a common gene pool

  3. After a population splits into two, microevolutionary changes such as mutations, natural selection and genetic drift can lead to genetic divergence between the groups

  4. With the accumulation of enough differences in their separate gene pools, the two groups can no longer produce fertile offspring even if they come in contact once again
• Prezygotic barriers


  • Habitat isolation
  • Temporal Isolation
  • Behavioral Isolation
  • Mechanical Isolation
  • Gametic Isolation
• Postzygotic barriers


  • Reduced Hybrid Viability
  • Reduced Hybrid Fertility
  • Hybrid Breakdown
• Speciation can take place with or without geographic separation
• Nomenclature


  The devising or choosing of names for things, especially in a science or other discipline; the body or system of names in a particular field
• First, phylogenetic trees are intended to show patterns of descent, not phenotypic similarity
• Second, we cannot necessarily infer the ages of the taxa or branch points shown in a tree
• Third, we should not assume that a taxon on a phylogenetic tree evolved from the taxon next to it