Chapter 24

• Origin of Species and Macroevolution


  The process of generating a new species
• Biologists use different characteristics to identify a species and will depend on the species in question
• Populations may be difficult to decide they are different species
• Morphological Traits


  • The physical characteristics of a population
  • May vary greatly
• Reproductive Isolation


  Prevents one species from successfully interbreeding with another species
• Molecular Features


  • DNA nucleotide sequences of genes
  • Gene order location along chromosomes
  • Chromosome structure
  • Chromosome number
• Ecological Factors


  • Food resources
  • Growth conditions
• Evolutionary Relationships


  Similarities in the shape/structure of bones or DNA sequences suggest an evolutionary relatedness
• If two organisms share an evolutionary relationship, that means they have a common ancestor on the evolutionary tree
• Species


  A group of individuals whose members have the potential to interbreed with each other in nature to produce viable, fertile offspring, but who cannot interbreed with members of other species
• Evolutionary Lineage Concept


  • Members of a species have shared in an evolutionary process and an evolutionary history
• Ecological Species Concept


  • Members of a species are adapted to a particular set of resources (niche) in the environment, which explains differences in form and behavior between species as adaptations to resource availability
• General Lineage Concept


  • All modern species concepts are variants of a single general concept of species
  • Uses species criteria that give contingent properties and are "standards for judging whether an entity qualifies as a species"
• Speciation


  The formation of a new species
• Underlying cause of speciation is the accumulation of genetic changes that ultimately promote enough differences within that group such that it is now different from the species from which it was derived
• Other causes of speciation

  • Abrupt events, such as changes in chromosome number, that results in reproductive isolation
  • Adaptation to different ecological niches
• Allopatric Speciation


  Speciation that occurs when populations are geographically isolated from one another
• Sympatric Speciation


  Speciation that occurs without geographic isolation