Bio 004, College of the Desert

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  1. Evolution

    Capacity of organisms to change over time through reproduction.

  2. Natural Selection
    Passage of beneficial genes to future generations while discouraging the passage of harmful genes.
  3. Lamarck and Evolutionary Adaptations
    • Point #1: Individual organisms may develop certain traits, by using or disusing body parts, that are in turn passed on to their offspring.

    • Point #2: Inheritance of acquired characteristics (example: the giraffe’s neck).

    • Flaw: Acquired characteristics are NOT inherited, but acquired after birth!

  4. Two Main Concepts in The Origin of Species
    • 1) Contemporary spp arose from a succession of ancestors through descent with modification.
    • 2) Natural selection = mechanism for evolution.
  5. Biogeography
    Distribution of species into various habitats (marsupial migration).
  6. Comparative Anatomy
    Comparison of body structures among different species.
  7. Homology
    Similarity in body structures due to common ancestry.
  8. Vestigial Organs
    Remnants of structures that served important functions in organisms’ ancestors
  9. Comparative Embryology
    Comparison of anatomical structures that appear during early development of different organisms.
  10. Two Key Observations
    • 1. Species tend to overproduce offspring.

    • 2. There exists variation among individuals within a population.

  11. Population
    • Group of organisms of the same species living in the same area at the same time

    • Smallest unit of evolution : Only populations evolve, not individuals

  12. Population Genetics
    Study of the genetic makeup of populations over time.
  13. Polymorphism
    Two or more variations of a phenotypic form present in noticeable numbers.
  14. Mutations

    Random generation of new alleles

  15. Meiosis

    Specifically synapsis, crossing-over, segregation, independent assortment.

  16. Fertilization
    Genes from two unique family lines uniting in the zygote.
  17. Hardy-Weinberg Principle

    Allele frequency – or the relative occurrence of certain traits –remain constant from one generation to the next.

  18. Hardy-Weinberg Principle Conditions
    • 1. Populations must be extremelylarge. Small populations increase allele fluctuations.

    • 2. No gene flow. Gene flow increases allele fluctuations.

    • 3. No mutations. Mutations modify the gene pool.

    • 4. Random mating. Random mating increases gamete mixing.

    • 5. No natural selection. Natural selection increases allele fluctuations.

  19. Genetic Drift
    Change in the gene pool of small population due to chance.
  20. Bottleneck Effect
    • Situation in which a drastic reduction in population size occurs resulting in a drastic reduction in genetic diversity.
    • Example: Cheetahs
  21. Founder Effect
    Establishment of a new population whose gene pool diverges from the parent population.
  22. Gene Flow

    Genetic additions to and/or sub-tractions from a population resulting from the movement of fertile individuals or gametes.

  23. Fitness

    Contribution an individual makes to the gene pool relative to the contributions of other individuals.

  24. Directional Selection
    • Natural selection that favors individuals at one end of the phenotypic range.

    • Example: black bear size in Europe during the ice ages - increased during glaciation, decreased during warming.

  25. Disruptive Selection
    • Natural selection that favors individuals on both extremes of a phenotypic range over intermediates.

    • Example: Black-bellied seedcracker finches of Cameroon - small bills for soft seeds, large bills for hard seeds – intermediate bills ineffective on both seed types.

  26. Stabilizing Selection
    • Black-bellied seedcracker finches of Cameroon - small bills for soft seeds, large bills for hard seeds – intermediate bills ineffective on both seed types.

    • Example: Human birth weights – if the newborn is under or overweight, infant mortality increases

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Bio 004, College of the Desert
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