Ecology- natural selection

genetic change over time through a process of descent with modification

evolution

acts on individuals but populations evolve

selection

genes have 2 or more forms

alleles

individuals with certain heritable traits survive and reproduce more successfully than other individuals

natural selection

possibility of different environmental conditions, different characteristics may be favored

speciation

population accumulates differences over time different from ancestors

modification descent

features of organisms that improve their ability to survive and reproduce

adaptations

traits that confer advantages tend to increase in frequency over time

adaptive evolution

3 things cause allele frequencies in population to change over time

natural selection, gene drift, gene flow

different alleles and change in DNA

mutation

3 type of natural selection

directional, stabilizing, disruptive

individuals at one phenotypic extreme

directional selection

individuals with an intermediate phenotype are favored

stabilizing selection

individuals at both phenotypic extremes are favored

disruptive selection

occurs when chance events determine which alleles are passed to next generation

• affects genes that not under selection

• significant for small populations

genetic drift

allele frequencies that reach 100% frequency

fixation

alleles move between populations via movement of individuals or gametes

gene flow

2 gene flow effects

similar populations, new alleles