Evolution Unit

• Adaptation


  A structure that helps an organism survive and reproduce in a particular environment
• Mimicry


  A structural adaptation with a harmless species resembles a harmful species in colouration or structure
• Variation


  Differences between individuals which may be structural, functional or physiological
• Mutation


  Permanent change in the genetic material of an organism
• Mutations happen continuously in the DNA of any living organism
• Possible effects of a mutation

  • Could die
  • Malfunction
  • Multiply more than it should
  • Can be harmful
  • Beneficial
  • Could have no effect at all (silent mutations)
• Selective Advantage


  A genetic advantage that improves an organism's chance of survival (changing environment)
• Bacteria reproduces quite quickly, doubling the population in as little as 10 mins
• Bacteria become resistant (antibiotic resistant)
• Natural Selection


  The process by which characteristics of a population change over many generations. Heritable traits survive and get passed to their offsprings
• Selective Pressure


  Environmental conditions that select for certain and against certain characteristics of individuals
• Artificial Selection


  Selection done by humans populations in order to modify particular traits
• Monoculture


  Extensive plantings of the same varieties of a species over large expanses of land
• Transitional Fossil


  Fossils that shows intermediary links between groups of organisms
• Transitional Fossil


  • Fossilized wales from 36 M.Y.A link present day wales to terrestrial ancestors
• Vestigial Features


  Features that were once useful
• Vestigial Features


  • Human ear muscles, du claw on dogs, extra digit on pig's feet, pelvic bone in the whale
• Biogeography


  The study of the past and present geographical distribution of organisms
• Darwin and Wallace hypothesis that species evolve in one location then spread to other regions
• Homologous Features


  Structures that have similar structural elements and origin but may have a different function
• Homologous Features


  • Vertebrate forelimbs demonstrates this (running, swimming, flying)
• Analogous Features


  Structures of organisms that do not have a common evolutionary origin but perform similar functions
• Analogous Features


  • Insect wings + Bat wings
• Mutation


  Mutation randomly introduces new alleles into a population
• Gene Flow (Migrations)


  Gene flow occurs between two different interbreeding populations that have different allele frequencies
• Non-Random Mating


  During non-random mating, individuals in a population select mates, often on the basis of their phenotypes
• Genetic Drift


  Genetic drift refers to random change in genetic variation from generation due to chance
• The Founder Effect


  A change in a gene pool that occurs when a few individuals start a new isolated population. Occurs frequently on islands
• The Bottleneck Effect


  Changes in gene distribution that result from a rapid decrease in a population size. Occurs from natural disasters, floods and human activity
• Natural Selection


  Natural selection is the result of the environment selecting for individuals in a population with certain traits that make them better suited to survive and reproduce than others in the population
• Types of Natural Selection

  • Stabilizing Selection: that favors intermediate phenotypes against extreme variations
  • Directional Selection: that favors the phenotypes one extreme to the other
  • Disruptive Selection: that favors the extremes of a range of phenotypes rather than intermediate phenotypes
• Speciation


  The formation of new species from existing species
• Prezygotic Isolation Mechanisms


  • Behavioral Isolation
  • Habitat Isolation
  • Temporal Isolation
  • Mechanical Isolation
  • Gametic Isolation
• Prezygotic


  Before a fertilized egg
• Post-Zygotic


  After an egg has been fertilized
• Hybrid inviability


  Development of the hybrid zygote is stopped
• Hybrid sterility


  Occasionally a hybrid is produced that is able to live
• Hybrid breakdown


  First generation of hybrids are viable and fertile but the second generation of hybrids are not viable and fertile