Natural selection and Evolution

• Population genetics


  Is the study of the gene pool and allele frequency distribution and change in populations over time.

  
• Genetic equilibrium


  Occurs when the frequency of alleles remains the same over generations within a population

  
• Gene pool


  The sum of the genetic information contained within a population of an organisms and it is often expressed as a frequency or number of genes.

  
• 5 Major evolutionary forces

  mutation, gene flow, genetic drift, natural selection, sexual selection
• Gene flow


  the process of genes moving from one population to another

  
• Genetic drift

  random change in allele frequency due to chance events in the population.

  
• Natural Selection


  The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

  
• Sexual Selection


  Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex.

  
• Variation


  Phenotypic differences between individuals in a population with a genetic basis

  
• Migration


  Movement of individuals or alleles into a population

  
• Speciation


  The process of formation of a new species

  
• Population


  The total number of all of the organisms of the same species living in the same area at the same time.
• Species


  A group of similar organisms that can breed and produce fertile offspring.
• Adaptations


  Change by which an organism/ species becomes better suited for its environment

  
• Coevolution


  Occurs when two species, found in the same area, effect each others evolution. (ex: Insects can influence how some plants change)

  
• Convergent evolution

  process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

  
• bottleneck affect

  a change in allele frequency following a dramatic reduction in the size of a population

  
• stabilizing selection


  Natural selection that favors intermediate variants by acting against extreme phenotypes. Middle

  
• directional selection


  shift of a population toward an extreme version of a beneficial trait;

  favors individuals at one end of the phenotypic range

  
• disruptive selection


  favors individuals at both extremes of the phenotypic range

  
• founder effect

  genetic drift that occurs after a small number of individuals colonize a new area
• Mutation


  A change in a gene that creates a new variation
• natural selection


  A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

  
• evolution

  Changes in a species' population over time.

  
• homologous structure


  similar structures inherited from a common ancestor (ex. birds wings, reptile limbs); however these structures have different functions.

  
• vestigial structure


  reduced or non-working structure that indicates shared common ancestry (ex. human appendix)

  
• analogous structure


  structure that has the same function but different structure and was not inherited from a common ancestor.

  
• embryo

  organism's early prebirth stages of development

  
• fossil records


  Provides record of species, shows similar characteristics between living and extinct

  
• adaptation


  Trait shaped by natural selection that increases an organisms reproductive success

  
• geographic isolation


  isolation between populations due to physical barriers

  
• artificial selection


  selection by humans through directed breeding (Breeding of useful traits from the natural variation) to produce offspring with desired traits.

  
• survival of the fittest


  process by which individuals that are BETTER suited to their environment survive and reproduce most successfully; often used interchangeably with the term 'natural selection'.

  
• genetic variation


  The variety of different types of genes in a species or population.
• competition

  the struggle between organisms to survive in a habitat with limited resources
• environmental changes


  change in environment that can affect an organism's ability to survive
• mutations


  a random error in gene replication that leads to a change

  
• Charles Darwin


  English natural scientist who formulated a theory of evolution by natural selection

  
• stabalizing selection

  natural selection that favors average individuals in a population; results in a decline in population variation. Getting rid of both extremes

  
• disruptive selection


  natural selection in which individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve