Ch. 17

Cards (20)

  • Microevolution is a change in allele frequencies within a population
  • Microevolution does not lead to the formation of new species
  • Macroevolution, or the origin of a new species, results from the accumulation of microevolutionary changes over time
  • Darwin dedicated his life to understanding how new species originate
  • Speciation is a form of macroevolution
  • Taxonomists are scientists who classify organisms into groups
  • Species can be defined in various ways, including:
    • Morphological Species Concept
    • Evolutionary Species Concept
    • Phylogenetic Species Concept
    • Biological Species Concept
  • Morphological Species Concept:
    • Species are distinguished by distinct physical characteristics
    • Helpful for paleontologists
    • Challenging for microorganisms and cryptic species
  • Evolutionary Species Concept:
    • Members share a distinct evolution in addition to morphological traits
    • Used to indicate speciation in the fossil record
  • Phylogenetic Species Concept:
    • Smallest set of interbreeding organisms that share a common ancestor
    • Monophyletic branch in the phylogenetic tree
    • Considers DNA and other factors
  • Biological Species Concept:
    • Relies on reproductive isolation to identify different species
    • Reproductive isolation defined by physiological, behavioral, and genetic processes
  • Reproductive Isolating Mechanisms:
    Prezygotic Isolating Mechanisms:
    • Geographic Isolation
    • Habitat/Ecological Isolation
    • Temporal Isolation
    • Behavioral Isolation
    • Mechanical Isolation
    • Gamete Isolation
    Postzygotic Isolating Mechanisms:
    • Hybrid Inviability
    • Hybrid Sterility
  • Allopatric Speciation is the most common form of speciation:
    • Species separated by a geographical barrier
    • Undergo different selection pressures
    • Competition leads to resource partitioning
  • Sympatric Speciation:
    • Speciation without a geographic barrier
    • Involves divergence in diet or microhabitats
    • Polyploidy is more likely in plants
  • Adaptive Radiation:
    • A single ancestral species gives rise to a variety of new species
    • Often involves sympatric species and ecological release
  • Convergent Evolution:
    • Occurs when biological traits evolve in two unrelated species due to exposure to similar environments
    • Examples include African lake fish with similar coloring/body
  • Principles of Macroevolution:
    • Gradualistic model
    • Punctuated equilibrium model
    • Developmental Genes and Macroevolution
  • Developmental Genes and Macroevolution:
    • Control switches for development are shared among all organisms
    • Examples include the Pax6 gene for the eye and Tbx5 gene for limbs
  • Human Evolution:
    • Humans have approximately 23,000 genes
    • Natural selection acts on variations that are already present
  • Macroevolution is not goal-oriented but opportunistic