Natural Selectoin & Genetic Drift

natural selection

individuals produce more offspring than environment can support (later dying)

• Those that survive pass genes off

• Overtime, larger proportion of pop. have those genes over a longer period of time

genetic drift

sudden random event (abrupt change) leads to sudden change in gene frequency (due to chance)

• some individual of population get eliminates = genes get terminated

• remaining pass genes off and over times will only see those specific genes

evolution

this measures changes in gene frequency in population from one generation to the next

• frequency includes gene increasing/decrease

• interplay of external events & internal response

antibiotic resistant bacteria

bacteria no longer killed by antibiotic; chemical puts pressure on bacteria resulting in mutation development and survive. In future offsprings genes will be passed on, and will results in larger population

• example for natural selection

binary fission & conjunction pili

the two mechanism that allow antibiotic resistance to happen

animal agricultural

this is an area where the most antibiotic is used in which results in antibiotic resistant

differential survival

natural selection is based on ____ ___ & reproduction of individuals within a population in response to environmental pressure

stabilizing selection

intermittent phenotype favored and adapt to stable environment over time (perfect conditions)

• ex: elephants and trees

• 1/3 types of N.S

directional selection

extreme rare phenotype favored; When their is LOTS of offspring & are adaptable to environment

• ex: antibiotic resistance & bed bug resistance to chemical

disruptive (diversifying) selection

2 or more extreme phenotypes favored

• ex: snails changing color of shell to adapt to environment

polymorphism

different forms/phenotypes in population of same species

random events

tornados, flooding hurricanes, blizzards, earthquakes or volcanoes

• genetic drift

large population

genetic drift less likely

small population

genetic drift more likely

• decrease in genetic diversity = more likely to go extinct

bottleneck effect

going forward from random event = genetic similarities

• most often

• ex: Cheetahs - last ice age killed pop = similar genes. Resulted in few offspring.

Founder effect

Two or more breeding individuals go to new location where species has never been before

• ex: wolves Isle Royale

inbreeding

increase in homozygous genotype (decrease genetic diversity)

flexibility

genetic diversity give population ___ to survive in changing environment.. more ways to adapt

gene flow

breeding individual go to new population & offspring allows gene variation

gene pool

various alleles at all the gene locations in all individuals