Biology II Exam I

• Modern definition of Evolution: Genetic change in population over multiple generations.
• The two aspects of evolution are Pattern of Evolutionary Change which is Observable data from the natural world and the Process of Evolution Mechanisms that produce the observed patterns of change.
• Genetic variation is the differences in alleles of genes found within individuals in a population.
• Evolution is how an entity changes through time.
• Pre Darwin thinking believed it was that species had remained unchanged since their creation.
• Darwin never used the word evolution in the first edition of The Origin of Species. The phrase descent with modification summarized Darwin’s perception of the unity of life.
• Darwin developed three main ideas, descent with modification explains life’s unity, diversity and how organisms are suited to life in their environments.
• Natural selection can lead to change in allele frequencies which is the frequencies of alleles of a gene from generation to generation.
• Genetic variation is required for evolution to occur.
• The Hardy–Weinberg principle Predicts genotype frequencies
• Hardy–Weinberg equilibrium says that proportions of genotypes do not change in a population as long as

  1. No mutation takes place
  2. No genes are transferred to or from other sources
  3. Random mating is occurring
  4. The population size is very large
  5. No selection occurs
• Hardy–Weinberg principle is the formula: $p 2 +$$2pq +$$q 2 =$$1$
• The 5 Agents of Evolutionary Change are Mutation, Gene Flow, Non-Random mating, Natural Selection, and Genetic Drift.
• The bottleneck effect can result from a drastic reduction in population size due to a sudden environmental change.

  Founder effect One or a few individuals disperse and become the founders of a new, isolated population.
• Artificial selection – breeder selects desired characteristics.

  Natural selection – environmental conditions determine which individuals produce the most offspring.
• These conditions must be met for evolution by natural selection to occur:

  1. Variation must exist among individuals in a population

  2. Variation among individuals must result in differences in the number of offspring surviving in the next generation

  3. Variation must have a genetic basis
• Fitness - Individuals with one phenotype leave more surviving offspring in the next generation than individuals with an alternative phenotype.
• Most fit phenotype is assigned fitness value of 1.
• Fitness has many components including Survival, Sexual selection, Number of offspring per mating and traits favored for one component may be a disadvantage for others.
• Parental Investment Refers to the energy and time each sex invests in producing and rearing offspring.
• Intersexual selection – mate choice
• Secondary sexual characteristics – antlers and horns used to combat other males; long tail feathers and bright plumage used to “persuade” members of opposite sex
• Sexual dimorphism – Differences between sexes (males larger than females)
• Sperm competition – selects for features that increase probability that a male’s sperm will fertilize the eggs
• Sensory exploitation – evolution in males of a signal that exploits preexisting biases
• Negative frequency-dependent selection -

  1. Rare phenotypes favored by selection.
  2. Rare forms may not be in “search image”; preyed upon less frequently.
• Positive frequency-dependent selection

  1. Favors common form.
  2. Tends to eliminate variation. •
  3. “Oddballs” stand out.
• Heterozygotes are favored over homozygotes because it works to maintain both alleles in the population.
• Types of selection

  1. Disruptive - Acts to eliminate intermediate types
  2. Directional - Acts to eliminate one extreme
  3. Stabilizing - Acts to eliminate both extremes
• Gene flow can be

  Constructive - Spread beneficial mutation to other populations. Constraining - Can impede adaptation by continual flow of inferior alleles from other populations.
• For more recent events, 14C half-life is 5700 years