Evolution Of Populations


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  • The Mummichog (Fundulus heteroclitus heteroclitus) is a small killifish found in the eastern United States. It is capable of tolerating highly variable salinity and temperatures, and is found in estuaries and saltmarshes as well as less salty waters. A year-round resident of tidal creeks and wetlands, this brownish-green saltwater minnow may reach a maximum length of 5 inches. Its Indian name means "they go in great numbers." It is also known as the common killifish. A hardy fish, the mummichog is an important food source for larger fish and is often used as bait. The mummichog also has been used as a natural method of mosquito control in marsh ponds and ditches. It has been reported that one mummichog can eat as many as 2,000 mosquito larvae ("wrigglers") a day. The mummichog also feeds on other insects, small fish, crustaceans, and plant material. Because of the extreme hardiness of the species, it is sometimes the only species found in severely polluted and oxygen-deprived streams, such as the Hackensack River and the Arthur Kill in New Jersey during the height of the water pollution problem in the United States. In 1973 the Mummichog became the first fish in space when carried on Skylab 3 as part of the biological experiments package later space missions by the U.S., such as Bion 3, have also carried Mummichog.
  • Bent Grass growing on mine tailings; only individuals tolerant of toxic heavy metals will grow from the seeds blown in from nearby field
  • Every individual has hundreds of mutations 1 in 100,000 bases copied 3 billion bases in human genome But most happen in introns, spacers, junk of various kind Not every mutation has a visible effect. Some effects on subtle. May just affect rate of expression of a gene.
  • 1 family has a lot of children & grandchildren therefore has a greater impact on the genes in the population than other families Genghis Khan tracked through Y chromosome.
  • Evolution Of Populations

    1. 1. Evolution of Populations Doonesbury - Sunday February 8, 2004
    2. 2. Populations evolve <ul><li>Natural selection acts on individuals </li></ul><ul><ul><li>differential survival due to various adaptations </li></ul></ul><ul><ul><ul><li>“survival of the fittest” </li></ul></ul></ul><ul><ul><ul><li>Results in differential reproductive success </li></ul></ul></ul><ul><ul><ul><ul><li>who bears more offspring </li></ul></ul></ul></ul><ul><li>Populations evolve </li></ul><ul><ul><li>genetic makeup of population changes over time </li></ul></ul><ul><ul><li>favorable traits (greater fitness) become more common </li></ul></ul><ul><ul><li>Gene pool within a population changes </li></ul></ul>
    3. 3. Changes in populations Insecticide resistance Insects that have resistant target sites will survive, making that trait more common in the population’s gene pool Pesticide molecule Insect cell membrane Target site Resistant target site Target site Decreased number of target sites
    4. 4. Individuals survive or don’t survive… Populations evolve Individuals are selected Individuals reproduce or don’t…
    5. 5. Fitness <ul><li>Survival & Reproductive success </li></ul><ul><ul><li>individuals with a more advantageous phenotype leave more surviving offspring </li></ul></ul>Body size & egg laying in water striders
    6. 6. Variation & natural selection <ul><li>Variation is the raw material for natural selection </li></ul><ul><ul><li>there have to be differences within populations or else gene frequency could not change </li></ul></ul><ul><ul><li>some individuals must be more fit than others </li></ul></ul>
    7. 7. Where does Variation come from? <ul><li>Mutation </li></ul><ul><ul><li>random changes to DNA </li></ul></ul><ul><ul><ul><li>errors in mitosis & meiosis </li></ul></ul></ul><ul><ul><ul><li>environmental damage </li></ul></ul></ul><ul><li>Sex </li></ul><ul><ul><li>mixing of alleles </li></ul></ul><ul><ul><ul><li>recombination of alleles </li></ul></ul></ul><ul><ul><ul><ul><li>new arrangements in every offspring </li></ul></ul></ul></ul><ul><ul><ul><li>new combinations = new phenotypes </li></ul></ul></ul><ul><ul><li>spreads variation </li></ul></ul><ul><ul><ul><li>offspring inherit traits from </li></ul></ul></ul><ul><ul><ul><li>both parents </li></ul></ul></ul>Mean beak depth of parents (mm) Medium ground finch 8 8 9 10 11 9 10 11 1977 1980 1982 1984 Dry year Dry year Dry year Wet year Beak depth Beak depth of offspring (mm)
    8. 8. 5 Agents of evolutionary change Mutation Gene Flow Genetic Drift Selection Non-random mating
    9. 9. 1. Mutation & Variation <ul><li>Mutation creates variation </li></ul><ul><ul><li>new mutations are constantly appearing </li></ul></ul><ul><li>Mutation changes DNA sequence </li></ul><ul><ul><li>changes amino acid sequence? </li></ul></ul><ul><ul><li>changes protein? </li></ul></ul><ul><ul><ul><li>changes structure? </li></ul></ul></ul><ul><ul><ul><li>changes function? </li></ul></ul></ul><ul><ul><li>changes in protein may change phenotype & therefore change fitness </li></ul></ul><ul><ul><ul><li>Changing survival and reproductive </li></ul></ul></ul><ul><ul><ul><li>rates </li></ul></ul></ul><ul><ul><ul><li>Changing gene frequencies </li></ul></ul></ul>
    10. 10. 2. Gene Flow <ul><li>Movement of individuals & alleles in & out of populations </li></ul><ul><ul><li>seed & pollen distribution by wind & insect </li></ul></ul><ul><ul><li>migration of animals </li></ul></ul><ul><ul><ul><li>causes genetic mixing across regions </li></ul></ul></ul><ul><ul><ul><li>reduce differences between populations </li></ul></ul></ul>
    11. 11. 3. Non-random mating <ul><li>Living things do not mate at random </li></ul><ul><li>Sexual selection – select for advantageous traits in a mate </li></ul><ul><ul><li>What is the best combination of traits to pass on to offspring to ensure survival? </li></ul></ul>
    12. 12. 4. Genetic drift <ul><li>Effect of chance events </li></ul><ul><ul><li>founder effect </li></ul></ul><ul><ul><ul><li>small group splinters off & starts a new colony </li></ul></ul></ul><ul><ul><li>bottleneck </li></ul></ul><ul><ul><ul><li>some factor (disaster) reduces population to small number & then population recovers & expands again </li></ul></ul></ul>Warbler finch Tree finches Ground finches
    13. 13. Conservation issues <ul><li>Bottlenecking is an important concept in conservation biology of endangered species </li></ul><ul><ul><li>loss of alleles from gene pool </li></ul></ul><ul><ul><li>reduces variation </li></ul></ul><ul><ul><li>reduces adaptability </li></ul></ul>Breeding programs must consciously outcross Peregrine Falcon Golden Lion Tamarin
    14. 14. 5. Natural selection <ul><li>Differential survival & reproduction due to changing environmental conditions </li></ul><ul><ul><ul><li>climate change </li></ul></ul></ul><ul><ul><ul><li>food source availability </li></ul></ul></ul><ul><ul><ul><li>predators, parasites, diseases </li></ul></ul></ul><ul><ul><ul><li>toxins </li></ul></ul></ul><ul><ul><li>Nature selects for the combinations </li></ul></ul><ul><ul><li>of alleles that provide “ fitness ” increase in the population </li></ul></ul><ul><ul><ul><li>adaptive evolutionary change </li></ul></ul></ul>
    15. 15. 5 Agents of evolutionary change Mutation Gene Flow Genetic Drift Selection Non-random mating