evolution

evolution

change in allele frequencies in a population over time

population

a group of organisms of the same species living in the same area

The four main mechanisms of evolution + another:

mutation, gene flow, genetic drift, and natural selection. (+ artificial selection.)

mutation

source of all variation, nearly all mutation have a neutral or negative effect on the fitness of an organism.

genetic drift

small population more vulnerable, change allele frequences due to chance, Won the game of chance(Luck), bottleneck effect, founder effect, bad effect, less varation

bottleneck effect (genetic drift)

fire in forest, survivors lived by luck (weren’t directly effected) → new allele frequences among the surviving population, Environmental disaster, quick drop in population size=less diversity

founder effect (genetic drift)

organisms that have founded an island or some new area (random sample, cotton flower blows in wind in new area) → don’t represent original population (sunflowers, roses), new founded population will match more to the founders than the entire population

gene flow

allele exchange between populations, usually good! bird AA flys to bird aa. new allele introduced

natural selection

only mechanism that makes individual survive best in environment, where organisms better adapted to their environment tend to survive and produce more offspring, if enivornment changes→ natural selection changes too

fitness

how many offspring they have

Three types of natural selection

Directional selection, stabilizing selection, disruptive selection

directional selection

the peak shifts in one direction, moths turning different colors based on color of bark

stabilizing selection

the peak becomes higher and narrower, selective pressure: too light or too heavy more complications, middle weight survive best and are healthy

disruptive selection

two peaks form, two traits favored at the same time, small-beaked birds ate soft seeds, large-beaked birds ate hard seed, no birds with medium sided survived bec they fed inefficiently

artificial selection

like natural selection, but people do the selecting, domestication of plants and animals, wild musterd plant→ cabbage, cauliflower, broccoli, kale, brussels sprouts