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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 1890

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

  7. Old growth piñon Only juniper occurs in the Gunnison Basin today

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

  9. Quiz • How would you define a population and a metapopulation? • What are three variables to consider in describing a population? • Give three good reasons for why one should study a population. • 4. What is demography and what are demographic variables?

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

  11. 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

  12. 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

  13. 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.

  14. Quiz • Give the formula for exponential growth of a population and does the intrinsic growth rate (r) change? • Give the formula for logistic growth. Explain carrying capacity (K) and how it relates to the intrinsic growth rate. • What are three density-dependent and three density- • independent factors that affect population growth? • When do populations undergo exponential growth? • What is the source-sink concept and the Allee effect in ecology?

  15. 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

  16. 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

  17. Robert MacArthur 1930-1972 Hypothetico-deductive method in ecology Competition and niche partitioning r and K selection in life history strategy Predator – prey theories Optimal foraging Island Biogeography Population growth and dynamics Generalist vs. specialist feeding Paper on reserve: Fretwell, S. 1975. The impact of Robert MacArthur on Ecology. Annual Review of Ecology and Systematics 6: 1-13.

  18. Quiz • What is the difference between semelparous and iteroparous reproduction and overlapping and non-overlapping generations? • What is an age structure diagram and what does its shape tell us about growth rate (r) for the population? • What are some differences between r-selected and K-selected species? What are some examples of each? • What is a cohort life table and what are Type I, II, and III survivorship curves? How do you calculate reproductive value (R0), generation time (T), and r using life table data? • Who was Robert MacArthur and what are some of his major contributions to the field of ecology?

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