BIOL 112 Final

• Homologous & Convergence


  First Topic
• Homologous Structures


  Structures derived from a common ancestor, may be modified for different functions
• Examples of Homologous Structures


  Human, cat, whale bat arms
• Vestigal Structures


  Remnants of ancestral (homologous) structures with no present adaptive function
• Convergence Structures


  Unrelated species have similar adaptions (analogous structures) under similar environmental conditions
• Convergent Evolution


  Natural selection acted in a way under some conditions (torpedo shape for swimming)
• Alleles


  Second Topic
• Allele


  One of a number of alternate forms of a DNA sequence at a particular genetic locus
• What has low mutation rates?

  Plants and animals
• Where do mutations happen faster and why?

  In prokaryotes because they have short generation times
• Crossovers, independent assortment, random fertilization


  Sexual reproduction can result in genetic variation by recombining alleles
• Microevolution


  Change in allele frequencies in a population over generations
• Popultion genetics


  The study of what changes the allele frequencies in populations
• Three mechanisms that cause allele frequency change


  1.) Natural Selection

  2.) Genetic Drift

  3.) Gene Flow
• Morphological Species Concept


  Third Topic
• Morphological Species Concept Definition

  Organisms that have significant morphological & anatomical differences are different species
• Example of Morphological Species Concept


  Sorting birds into species based on their wingspan & beak size
• Biological Species Concept


  Fourth Topic
• Biological Species Concept Definition

  Organisms that are reproductively isolated from each other are different species
• Members of the same biological species


  -Share the same gene pool

  (there gene flow between species)

  -Reproductively isolated from other species (by natural biological barriers)
• Biological Reproductive Barriers


  Fifth Topic
• Prezygotic Barriers


  Act before the zygote is formed
• Temperal Isolation


  Species have different breeding schedules
• Habitat Isolation


  Members of a species move or are seperated
• Behavioural Isolation


  Actions or behaviours impacts reproduction
• Gametic Isolation


  Differences in gamete cells prevent fertilization
• Postzygotic Barriers


  Act after hybrid zygote is formed
• Hybrid Inviability


  An embryo is produced, but cannot survive development
• Hybrid Sterility


  Different species produce a viable offspring, but they can't reproduce
• Hybrid


  2nd generation hybrids are feeble or sterile
• Forms of Natural Selection


  Sixth Topic
• 1.) Directional Selection


  -Selects phenotypes at one end of the spectrum of existing variation

  -Shifts the populations genetic variance toward the new, fit phenotype
• 2.) Diversifying Selection


  -Intermediates are less fit than extremes

  -Maintains diversity

  -Increases genetic variance
• 3.) Stabilizing Variation


  -Intermediate types more fit than extremes

  -Decreases genetic variation
• 4.) Frequency Variation


  -The fitness of a phenotype depends on how common it is in the population
• 5.) Sexual Selection


  -Success based on traits related to obtaining mates (not directly related to the environment)

  -Leads to sexual dimorphism
• Intrasexual Selection


  Individuals of one sex compete directly for mates of the opposite sex
• Intersexual Selection


  Individuals of one sex are choosy in selecting their mates from the other sex

  -Typically female
• Genetic Variation


  Seventh Topic
• Genetic Variation Definition


  New genes and alleles can arise by mutation or gene duplication