bio ecology

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bio ecology
2011-05-13 19:02:03

chap. 36 population ecology
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  1. Population ecology is concerned with:
    • Changes in population size
    • Factors that regulate population over time
    • Essentially, how and why populations change
  2. Population
    • A group of individuals of a single species that occupy the same general area
    • Described by the number and distribution of individuals
  3. Individuals in a population:
    • Rely on the same resources
    • Are influenced by the same environmental factors
    • Are likely to interact and breed with one another
  4. Population ecology
    The study of how and why populations change
  5. Cause of variation in population sizes
    • A population increases through birth and immigration
    • Death and emigration out of an area decrease the population
  6. Population dynamics
    The interactions between biotic and abiotic factors
  7. Population density
    • The number of individuals of a species per unit area or volume
    • Ecologists use a variety of sampling techniques to estimate population densities
  8. Examples of population density:
    • The number of oak trees per square kilometer in a forest
    • The number of earthworms per cubic meter in forest soil
  9. Important population variables
    Density and dispersion patterns
  10. Dispersion pattern of a population
    Refers to the way individuals are spaced within their area
  11. Dispersion patterns can be:
    • Clumped
    • Uniform
    • Random
  12. Clumped pattern
    Individuals are grouped in patches
  13. Uniform pattern
    Individuals are equally spaced in the environment
  14. Random pattern
    The individuals in a population are spaced in an unpredictable way
  15. Life tables
    Track survivorship over the life span of individuals in a population
  16. Survivorship curves
    • Plot the proportion of individuals alive at each age
    • Type 1, Type 2, and Type 3
  17. Exponential growth model
    • The rate of population increases under ideal conditions
    • Calculated using the equation G=rN; G is the growth rate, N is the population size, r is the per capita rate of increase
  18. Logistic growth model
    • This growth model takes into account limiting factors
    • Limiting factors are environmental factors that restrict population growth
  19. Boom-and-bust cycles
    • Food shortages
    • Predator-prey interactions
  20. Age structure diagram
    Reveals a population's growth trends
  21. US Census Bureau projection
    • 8 billion people within the next 20 years
    • 9.5 billion by the mid-21st century
  22. Ecological footprint
    Helps understand resource availability and usage