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Population Dynamics

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Population Dynamics

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    1. Population Dynamics Factors influencing the expansion, decline or maintenance of populations A key to: Preventing population declines Control of pest species Maintenance of important species

    2. Properties of Populations Before: Distribution of species in space Movement among Distribution of individuals Abundance of individuals

    3. Properties of Populations Now: Population structure Stable, expanding, or declining How will they change over time?

    4. Population Size

    5. Population Size To predict change Must know patterns of births Must know patterns of deaths Or patterns of survival

    6. Dispersal Can increase or decrease local population size Ongoing dispersal can join subpopulations to form a metapopulation Under studied

    7. Dispersal

    8. Patterns of Survival

    9. Patterns of Survival How do we estimate the likelihood of surviving to a certain age? Cohort life table Static life table Age distribution

    10. Cohort Life Table Cohort: group of individuals born in the same time period Follow cohort until all die Historically accurate but not helpful for management

    11. Static Life Table Sample population at one point in time Generate age distribution Determine proportion of population at each age class Determine age at time of death Age skulls

    12. Aging Organisms

    13. Gray Squirrel Life Table

    14. Gray Squirrel Survivorship

    15. Bull Trout Survivorship

    16. Bull Trout Survivorship

    17. Dall Sheep Survivorship

    18. Dall Sheep

    19. Survivorship Curves

    20. Survivorship Curves

    21. Survivorship Curves Type I High survival among young Low survival among old Humans & other large vertebrates Some annual plants and inverts On shortened time scale

    22. Survivorship Curve Type II Nearly constant rate of survival Many birds, reptiles, small mammals, and plants

    23. Survivorship Curve Type III High mortality among young Marine fish Many trees, invertebrates

    25. Age Distribution One way to get static life table Also can suggest Population growing Population declining Population stable

    26. Age Distribution

    27. Age Distribution

    28. Age Distribution

    29. Age Distributions

    30. Population Size To predict change Must know patterns of births Must know patterns of deaths Or patterns of survival

    31. Birth Rate Measures production of new individuals Seed production Eggs laid New shoots with vegetative repro Cell division for bacteria Babies born

    32. Birth Rate Usually changes with age Calculate average # births per individual of each age = mx For sexual species completely ignore males in life tables # females and their # daughters

    33. Gray Squirrel Birth Rate

    34. Gray Squirrel Production

    35. Net Reproductive Rate R0 = net reproductive rate R0 = ?lxmx R0 > 1 --> population growing R0 < 1 --> population declining R0 = 1 --> no growth, replacement

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