- Slides: 14
Mechanisms of Evolution
Mechanisms of Evolution There are several: 1. Natural Selection 2. Gene Flow 3. Genetic drift 4. Mutations 5. Non-random mating
1. Natural Selection: • Variation exists within a population • More offspring are born than can survive • Phenotypic differences result in differential reproductive success • Individuals that do survive, pass heritable traits on to offspring • Over time (many generations) this could lead to changes in the population
2. Gene Flow: § Is the movement of alleles into or out of a population (immigration or emigration). § Gene flow can introduce new alleles into a gene pool or can change allele frequencies. § Example: § Plant pollen being blown into a new area
3. Genetic Drift § The change in allele frequencies as a result of random chance. § Affects small populations.
Examples of Genetic Drift § B) Population Bottleneck: § Occurs when a population undergoes an event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing. • The event may eliminate alleles entirely or also cause other alleles to be over-represented in a gene pool. EX. Cheetahs
4. Mutations § Are inheritable changes in the genotype. § Provide the variation that can be acted upon by natural selection. § Mutations provide the raw material on which natural selection can act.
5. Non-Random Mating § In animals, non-random mating can change allele frequencies as the choice of mates is often an important part of behavior. § **Dog Breeders**
§ Mimicry Coral snakes (venomous) and king snakes (non-venomous) The harmless king snake mimics the poisonous coral snake, causing would-bepredators to avoid them. http: //3. bp. blogspot. com Monarchs (toxic to predators) and viceroys (non-toxic) The viceroys mimics the coloration and pattern of the unpalatable monarch, also avoiding wouldbe-predators. http: //fish. mongabay. com Camouflage: A flounder will be less conspicuous to predators and to would-be prey if it blends in with its environment. http: //conservationreport. files. wordpress. com. Compare/contrast mimicry and camouflage. Pick an organism and explain the benefit of that animal or pl