Topic H

• Theory explains natural phenomena and is supported by many observations
• Evolution is defined as descent with modification
• Transitional (intermediate) fossils share features from multiple types of organisms
• Derived traits are features that do not appear in fossils of a common ancestor
• Ancestral traits are more primitive features that appear in ancestral forms
• Homologous structures are body structures inherited from a common ancestor, showing similar construction of internal features, but external surfaces may be adapted for specific functions
• Vestigial structures have reduced or no function in an adult organism
• An embryo is the early, pre-birth stage of development
• Convergent evolution

  1. Two or more distinct species share traits not due to a common ancestor

  2. Examples: birds, bats, and butterflies with wings for flying
• Convergent evolution


  Species share a trait not due to a common ancestor
• In convergent evolution, species share traits independently without a common ancestor
• Wings in birds, bats, and butterflies are examples of convergent evolution where the ability to fly is shared without a common ancestor
• Divergent evolution

  1. Two or more distinct species share a common ancestor from which they both diverged

  2. Examples: modern elephant and woolly mammoth, dog, wolf, and Fox
• In divergent evolution, species evolve independently and uniquely from a common ancestor
• Divergent evolution


  Descendants of a common ancestor evolved independently and uniquely
• Gradualism

  • Observed in the fossil record by looking at similar but different species to compare and see small changes
• Both gradualism and punctuated equilibrium are accepted as viable processes of evolution, and it may even be a combination of both that occurs
• Punctuated equilibrium


  A long time with no change (equilibrium) followed by a sudden large change in a short amount of time (punctuated portion)
• Gradualism


  Small changes in evolution over time.
• Hardy-Weinburg Principle

  $p+$$q=$$1$

  $p^2+$$2pq+$$q^2=$$1$
• Frequency = total of that allele/total # of alleles
• Directional Selection - graph shifts to one extreme or the other

  
• Disruptive Selection - shifts to both extremes and dips in the middle

  
• Stabilizing Selection - pinches in the middle and both extremes are selected against

  
• gene pool - all of the genes in a population
• natural selection - the process by which individuals with certain inherited characteristics are more likely to survive and reproduce
• fitness - the ability of an organism to survive and reproduce in its environment
• gene flow (movement) - the movement of genes from one population to another
• mutation - a change in the DNA sequence of a gene that can lead to a change in the population's allele frequency
• sexual selection - the process by which individuals are selected for traits that increase their reproductive success
• genetic drift (death) - when a population shrinks
• founder effect - when a small group of individuals leave a population and start a new one
• bottlenecking - when a large sum of the population is randomly eliminated
• Founder effect and bottlenecking are examples of genetic drift.
• Fill in the blank for which events go on which finger:

  1. thumb - natural selection
  2. pointer - gene flow
  3. middle - mutation
  4. ring - sexual selection
  5. pinky - genetic drift
• spandrel - a byproduct of evolution that has no significance