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biology-evolution 2

what does the pinkie stand for? small population
what does the ring finger stand for? non-random mating
what does the middle finger stand for? mutation
what does the pointer finger stand for? gene flow
what does the thumb stand for? adaptations
microevolution -occurs over a relatively short period of time within a population species -finches
macroevolution -occurs over geologic time above the level of species -fossil record
population consists of organisms of the same species that live in the same area where mating takes place
population genetics the science that focuses on evolution within population
gene pool consists of all the genes of all the members of the population
Hardy-Weinburg equilibrium describes populations in which allele frequencies are not changing
what factors are the forces of evolution? 1. mutation 2. gene flow 3. genetic drift 4. natural selection
how do all new alleles first rise? mutation
what mutations matter for evolution in sexually reproducing species? those that occur in gametes, only these can be passed on to offspring
gene flow occurs when individuals move in or out of a population
genetic drift a random change in allele frequencies that occurs in a small population
what are the two special conditions in which genetic drift occurs? -bottleneck effect -founder effect
bottleneck effect -occurs when a population suddenly gets much smaller -natural disaster -allele frequencies of the survivors may be different from those of the original population
founder effect -occurs when a few individuals start, or found, a new population -allele frequencies of the founders may be different from allele frequencies of the population they left
natural selection -occurs when there are differences in fitness among members of a population -some individuals pass more genes to the next generation
what are the three ways natural selection can affect phenotypes? 1. stabilizing selection 2. directional selection 3. disruptive selection
stabilizing selection -occurs when phenotypes at both extremes of the phenotypic distribution are selected against -narrows the range of variation
directional selection -occurs when one of two extreme phenotypes is selected for -this shifts the distribution toward that extreme -finches
disruptive selection -occurs when phenotypes in the middle of the range are selected against -results in two overlapping phenotypes, one at each end of the distribution -sexual dimorphism
sexual dimorphism refers to differences between the phenotypes of males and females of the same species
speciation the process by which a new species evolves
species a group of organisms that can breed and produce fertile offspring together in nature
how can a new species arise? some members of a species must become reproductively isolated from the rest of the species
allopatric speciation -members of a species become geographically separated from the rest of the species -if they remain separated enough, they may evolve genetic differences -differences prevent them from interbreeding with members of the original species..NEW SPECIES
sympatric speciation new species that arises without geographic separation
coevolution species in symbiotic relationships tend to evolve together, as one species changes, the other species must also change
gradualism -when geologic and climate conditions are stable, evolution may occur gradually -gradual loss of structure -darwin
punctuated equilibrium -when geologic and climate conditions are changing, evolution may occur more quickly -long periods of little change may be interrupted by bursts of rapid change -attributed to a mutation in a few essential genes -fossil record
what is in microevolution? -mutation -selection -gene flow -genetic drift
what is in macroevolution? -speciation -coevolution -gradualism -punctuated equilibrium
how can the absolute age of a fossil be found? -radiometric dating -determining layer of rock where the fossil was found
evolutionary/phylogenetic tree the age and appearances of fossils can be used to place fossils in sequences that often show patterns of changes that have occurred over time
phyletic speciation -abrupt mutations in a few regulatory genes occur after a species has existed for a long period of time -results in the entire species shifting to a new species -relate to punctuated equilibrium
divergent speciation -gradual accumulation of small genetic changes results in subpopulation of a species that eventually accumulate so many changes that the subpopulations become different species -gradualism
Created by: amandathornton