Unit 11 7 F Analyze and evaluate the

Unit 11 7 F Analyze and evaluate the effects of other evolutionary mechanisms, including genetic drift, gene flow, mutation, and recombination.

Let’s remember… • An allele is an alternative form of one gene B stands for black b stands for brown The allele would be…

Genetic Drift • An evolutionary mechanism in which allele frequencies change in a population

Allele frequency changes due to… • Natural disaster like flood, fire, or earthquake • A random change of the population (some are eliminated) • Different from natural selection b/c its by chance or randomly

Original Pop after change R = red star r = green heart 6 R, 5 r 5 r

Bottleneck Effect • The change in allele frequency where only genes of the surviving population members can be passed to future generations

Gene Pool • the sum of all the genes in an interbreeding population

Gene Pool • 2 blue alleles • 1 red allele • 12 green alleles

Founder Effect • The change in allele frequency in a gene pool that changes from a large population to a small population • Ex: small number of individuals get separated from a larger population… the change in the allele frequency is the founder effect

Founder Effect

Gene Flow • Occurs when the genes of 1 population flow into a different population • This change causes a shift in allele frequency

Immigration • Alleles move INTO a population

Emigration • Alleles move OUT OF a population

Lots of gene flow… • Slows down evolution • Lots of new alleles coming into and out of a population • More genetic variation within a population • Makes 2 populations more similar

Lack of gene flow… • Less variation within a population • Makes 2 populations more different and separates them

Mutation • Any change in the genetic material of a cell • Can occur within individual genes OR • Can involve changes in piece of chromosomes

• If the mutation is beneficial to the organism, the mutation will be passed on to offspring • Slowly over time the mutation will become more common in a population

Recombination • A source of heritable variation • Occurs for 2 reasons: a. Independent assortment b. Crossing over

Independent Assortment

Crossing Over

Hardy-Weinberg Principle • States that allele frequencies in a population will remain constant unless one ore more factors cause those frequencies to change

Hardy-Weinberg Equation Homozygous Heterozygous Homozygous dominant recessive 2 P + 2 pq + 2 q = 1 p = dominant allele frequency q = recessive allele frequency

Genetic Equilibrium • The situation in which allele frequencies remain constant (don’t change) • If frequencies don’t change, the population doesn't evolve

Conditions required to maintain genetic equilibrium: 1. 2. 3. 4. 5. Random mating Population must be large No immigration or emigration No mutations No natural selection