Modern Experimental evolution

1 modern

1.1 aphids
1.2 fruit flies
1.3 bacteria

1.3.1 lenski s e. coli experiment


1.4 laboratory mice
1.5 other examples

modern

experimental evolution has been used in various formats understand underlying evolutionary processes in controlled system. experimental evolution has been performed on multicellular , unicellular eukaryotes, prokaryotes, , viruses. similar works have been performed directed evolution of individual enzyme, ribozyme , replicator genes.

aphids

in 1950s, soviet biologist georgy shaposhnikov conducted experiments on aphids of dysaphis genus. transferring them plants or unsuitable them, had forced populations of parthenogenetic descendants adapt new food source point of reproductive isolation regular populations of same species.

fruit flies

one of first of new wave of experiments using strategy laboratory evolutionary radiation of drosophila melanogaster populations michael r. rose started in february, 1980. system started ten populations, 5 cultured @ later ages, , 5 cultured @ ages. since more 200 different populations have been created in laboratory radiation, selection targeting multiple characters. of these highly differentiated populations have been selected backward or in reverse, returning experimental populations ancestral culture regime. hundreds of people have worked these populations on better part of 3 decades. of work summarized in papers collected in book methuselah flies.

the experiments in flies limited studying phenotypes molecular mechanisms, i.e., changes in dna facilitated such changes, not identified. changed genomics technology. subsequently, thomas turner coined term evolve , resequence (e&r) , several studies used e&r approach mixed success 1 of more interesting experimental evolution studies conducted gabriel haddad s group @ uc san diego, haddad , colleagues evolved flies adapt low oxygen environments, known hypoxia. after 200 generations, used e&r approach identify genomic regions selected natural selection in hypoxia adapted flies. more recent experiments have started following e&r predictions rnaseq , genetic crosses. such efforts in combining e&r experimental validations should powerful in identifying genes regulate adaptation in flies.

bacteria

bacteria have short generation times, sequenced genomes, , well-understood biology. therefore commonly used experimental evolution studies.

lenski s e. coli experiment

one of known examples of laboratory bacterial evolution long-term e.coli experiment of richard lenski. on february 24, 1988, lenski started growing twelve lineages of e. coli under identical growth conditions. when 1 of populations evolved ability aerobically metabolize citrate growth medium , showed increased growth, provided dramatic observation of evolution in action. experiment continues day, , longest-running (in terms of generations) controlled evolution experiment ever undertaken. since inception of experiment, bacteria have grown more 60,000 generations. lenski , colleagues regularly publish updates on status of experiments.

laboratory mice

mouse garland selection experiment attached running wheel , rotation counter.

in 1998, theodore garland, jr. , colleagues started long-term experiment involves selective breeding of mice high voluntary activity levels on running wheels. experiment continues day (> 65 generations). mice 4 replicate high runner lines evolved run 3 times many running-wheel revolutions per day compared 4 unselected control lines of mice, running faster control mice rather running more minutes/day.

female mouse litter, garland selection experiment.

the hr mice exhibit elevated maximal aerobic capacity when tested on motorized treadmill. exhibit alterations in motivation , reward system of brain. pharmacological studies point alterations in dopamine function , endocannabinoid system. high runner lines have been proposed model study human attention-deficit hyperactivity disorder (adhd), , administration of ritalin reduces wheel running approximately levels of control mice. click here mouse wheel running video.

other examples

stickleback fish have both marine , freshwater species, freshwater species evolving since last ice age. freshwater species can survive colder temperatures. scientists tested see if reproduce evolution of cold-tolerance keeping marine sticklebacks in cold freshwater. took marine sticklebacks 3 generations evolve match 2.5 degree celsius improvement in cold-tolerance found in wild freshwater sticklebacks. microbial cells , mammalian cells evolved under nutrient limiting conditions study metabolic response , engineer cells better characteristics.