[HS BIO 002] Lesson 2: Evolution

• Evolution refers to change in the heritable characteristics.
• These heritable characteristics are the "expression of genes".
• Population refers to a group of individuals of the same species.
• Gene Pool are all alleles of a population's genes.
• Allele Frequency is the percentage of any one specific allele.
• Variations are differences among members of a species.
• If the allelic frequency stays the same ober many generations, it is called Generic Equilibrium.
• Phenotype is the physical expression of genes.
• Genotype is the genetic expression of genes.
• What are the Mechanisms of Evolution?

  • Non-Random Mating

  • Mutation

  • Genetic Drift

  • Gene Flow

  • Natural Selection
• It is called Non-Random Mating if organisms can choose their mating partners.
• Mutation happens when the parents' DNA results in offspring with different alleles which causes in change of the allele frequency.
• Genetic Drift happens when population change by chance.
• Gene Flow (Migration) are any movement of genes from one population to another.
• Natural Selection happens when individuals with the best adapted phenotypes will survive and pass on their genes to the next generation.
• Selection is a process whereby organisms that are better adapted to their environmental survive and reproduce, while those less failed to do so.
• Two types of Selection: Natural Selection & Artificial Selection
• Charles Darwin proposed this theory.
• Natural Selection is a theory that explains why organisms seem to match their environmental niches so well.
• Charles Darwin proposed this theory in his publication called “On The Origin of Species”.
• Fitness describes how successful an organism bas been at passing on its genes.
• Types of Natural Selection: Stabilizing Selection, Disruptive Selection, Directional Selection, Sexual Selection, & Polymorphism.
• Disruptive Selection is a selection which favors individuals of both extremes of a characteristic range.
• Directional Selection occurs when a certain allele has greater fitness than others.
• Sexual Selection is a selection that acts on traits that help animals increase their chances of mating.
• Polymorphism are different phenotypes found in a population, each group represents a morph (form).
• Artificial Selection is a process of intentional or unintentional modification of a species.
• Selective Breeding is choosing to breed plants or animals because they have desirable characteristics.
• Example of Selective Breeding is Dog Breeding.
• Negative Effects of Artificial Breeding:

  1. Removes variation in a population
  2. Organisms can be suspectible to diseases or changes in the environment.
• Stabilizing Selection is a selection favors intermediate variants.