Unit 1

• Direct Benefits hypothesis


  Females choose males that provide resources that directly improve the # of fertile offspring they can provide
• Direct Benefits hypothesis


  • Resources to benefit the female (food for self)
  • Resources to benefit offspring (food for young)
• Good Genes Hypothesis


  Suggests that females choose mates on traits that indicate the males ability to pass on genes that will increase the survival & reproductive success of offspring
• Good Genes Hypothesis


  • Females looking for males that will contribute good genes to offspring
  • Select males based on genetic quality
• Sexy Sons hypothesis


  Choosing mates with attractive traits will produce offspring who will inherit attractive traits
• Sexy Sons hypothesis


  • Offspring with attractive traits will be reproductively successful (high fitness) and thus spread the choosy mate's gene successfully
• Handicap hypothesis


  Predicts that secondary sexual traits are reliable indicators of quality because they are costly & reduce survival
• Handicap hypothesis


  • Peacocks train
• Good Genes


  Genetically superior mates produce fitter offspring
• Sexy Sons


  Females that mate with preferred fathers produce sons that will have high mating success
• Genetic Drift


  The fluctuation in gene frequencies that occurs by chance; occurs in all natural populations
• Genetic Drift


  • Random events, natural disasters
• Gene Flow


  The movement of individuals & alleles in/out of populations
• Gene Flow


  • Seed/pollen distributed by wind
  • Migration of animals
  • Movement of animals via human activity
• Immigration


  New individuals arrive from a different population
• Emigration


  Individuals leave one population to go to another
• Mutations


  Changes in DNA sequence, new mutations constantly appearing
• Directional selection


  Selective pressure favors the most extreme value of a trait in one direction only
• Stabilizing selection


  Selective pressure of a population favors an intermediate phenotype
• Disruptive selection


  Selective pressure favors the extreme phenotypes in either direction, may cause populations to split and become bimodal – two lumps
• Intersexual selection


  Mate choice; between sexes
• Intrasexual selection


  Mate competition; within a sex
• Intrasexual selection


  • Male narwals fight each other with horns for the opportunity to mate with females
• All traits that increase an individual's ability to attract mates are adaptations
• Allele frequencies fluctuate more in small populations
• Fitness is determined by how many offspring an individual has
• Natural selection is a mechanism of evolution
• Artificial selection


  When humans intervene to select and breed for specific traits in agricultural products or animals
• Natural selection


  Slow, organic process where organisms adapt to their environment to survive and reproduce
• Sexual selection


  A form of natural selection where the opposite sex is attracted to certain characteristics of the other sex
• Requirements for artificial, natural, and sexual selection

  • Genetic variation/diversity
  • Heritability
  • Differential/intentional selection
• Observation


  What you see; use your sense
• Inference


  Guess based on the information