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Population

Population A group of individuals of the same species that interact with each other in the same place at the same time. Metapopulation A population of populations, linked by genetic exchange (immigration and emigration). Describing a Population Distribution: total geographic range

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Population

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  1. Population • A group of individuals of the same species that interact with each other in the same place at the same time Metapopulation A population of populations, linked by genetic exchange (immigration and emigration)

  2. Describing a Population • Distribution: total geographic range • including gaps Density: number of individuals per area Dispersion: how individuals are dispersed

  3. Fig. 9.8

  4. Why Study a Population? Explain distributions Changes over time Absences from suitable habitats

  5. European Starling: 160 released in NY Central Park in 1860

  6. Zebra Mussel: larvae released in ship ballast in Great Lakes, 1988

  7. How to study populations? Select sample population and study growth over time Determine birth and death rates, average life span, and other demographic variables

  8. Demography: the vital statistics of a population • Reproduction • semelparous • iteroparous • nonoverlapping generations • overlapping generations

  9. Usually, long-lived species are iteroparous with overlapping generations e.g., bear, humans, elephant Short-lived species are more often semelparous with nonoverlapping generations e.g., insects, weeds Exceptions include salmon, agave, bamboo -- all are long-lived, but breed once and die These categories are important to know when trying to determine r for a species

  10. Importance of Age Structure in a Population • Humans: • 0-12 yr no births, r is – • 13-25 r + and high • 26-35 r + and low • 36-45 r + and very low • 46-80 r = 0 or - • The proportion of individuals in each age class • defines the age structure for the population

  11. Age structure for three countries Fig. 9.14 If r for each age class remains constant, the shape of the diagram will not change. Then, it’s a stable age distribution.

  12. r-selected • high r • short-lived • small size • short generation time • large litters, >1 per yr • unstable habitats • Type III survivorship • N variable below K • r-selected • high r • short-lived • small size • short generation time • large litters, >1 per yr • unstable habitats • Type III survivorship • N variable below K • r-selected • high r • short-lived • small size • short generation time • large litters, >1 per yr • unstable habitats • Type III survivorship • N variable below K • K-selected • low r • long-lived • large size • long generation time • small litters, 1 per year • stable habitats • Type I or II survivorship • N at or near K • K-selected • low r • long-lived • large size • long generation time • small litters, 1 per year • stable habitats • Type I or II survivorship • N at or near K • K-selected • low r • long-lived • large size • long generation time • small litters, 1 per year • stable habitats • Type I or II survivorship • N at or near K

  13. http://www.bcsturgeon.com/sturgeon.htm http://www.worldagroforestrycentre.org/ Sturgeon lives ~100 yrs female produces 1 million eggs, more eggs as it ages Giant bamboo lives ~250 yrs flowers once, 1000s of seeds Species with mixture of r and K-selected traits

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