population ecology

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Siobhan
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152342
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population ecology
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2012-05-05 15:21:49
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population ecology
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population ecology
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  1. Biosphere
    • Biosphere: is the enormous ecosystem that encompasses all of Earths habitable surface

  2. Two opposing forces determine birth and death rates
    • Biotic potential: the theoretical maximum rate at which a population could increase, assuming a maximum birth rate and minimal death rate
    • Environmental resistance: refers to the curbs on population growth that are set by the living and nonliving environment

    In nature, the interaction between biotic potential and environmental resistance usually results in a balance between the size of a population and the resources available to support it


  3. Population growth is a function of the birth rate, the death rate, and population size
    • growth rate (r) = rate of natural increase,
    • (doesnt account for immigration/emigration)

    r (growth rate) = b (birth rate) – d (death rate)

    • Example for a population
    • r = 0.15 (b) – 0.05 (d) = 0.1 = 10% per year

  4. exponential growth
    • If births exceed deaths by a constant percentage, population growth produces a J-curve
  5. boom and bust cycle
    • favorable growth conditions occur, population booms
    • Nutrients are depleted, and water temperature falls
  6. invasive species
    • Exponential growth occurs when individuals invade a new habitat
    • Invasive species: introduced into ecosystems where they did not evolve and where they encounter little environmental resistance ; lack of natural predators
  7. logistic population growth
    • The is callogistic population growth: populations increase to the maximum number sustainable by their environment and then stabilize
    • led its carrying capacity (K) : maximum population size that can be sustained by an ecosystem for an extended time without damage to the ecosystem

    • it results in an S-shaped growth curve, or S-curve
  8. carrying capacity (K)
    • led its carrying capacity (K) : maximum population size that can be sustained by an ecosystem for an extended time without damage to the ecosystem

    • it results in an S-shaped growth curve, or S-curve

  9. Environmental resistance limits population growth
    • The is callogistic population growth: populations increase to the maximum number sustainable by their environment and then stabilize
    • led its carrying capacity (K) : maximum population size that can be sustained by an ecosystem for an extended time without damage to the ecosystem

    • it results in an S-shaped growth curve, or S-curve

  10. The S-Curve of Logistic Population Growth
    • population grows rapidly
    • Growth rate slows
    • Frowth stops and the population stabilizes close to carrying capacity.

  11. Example- The Effects of Exceeding Carrying Capacity
    • when reindeer were introduced onto an island with no large predators, their population increased rapidly, seriously overgrazing the vegetation they relied on for food

  12. Environmental resistance can be classified into two broad categories
    • Density-independent factors, which limit population size regardless of the population density
    • Density-dependent factors, which increase in effectiveness as the population density increases
    • Nutrients, energy, and space are all density-dependent regulators of population size
  13. Density-dependent factors
    • Density-dependent factors become more effective as population density increases
    • Many mammals develop thick coats and store fat; some hibernate
    • Many birds migrate long distances to find food and a hospitable climate
    • Tree and bushes enter dormancy, dropping leaves and slowing their metabolic activities

  14. Important density-dependent factors limiting population growth are:
    • Predation
    • Parasitism
    • Competition
  15. Some predator-prey population cycles
    • Some predator-prey population cycles are out-of-phase when predators cause a dramatic decline in prey populations, which in turn results in a decline in the predator population at a future date
  16. Competition
    • Competition :interaction among individuals who attempt to use the same limited resource, and this interaction limits population size in a density-dependent manner
    • intraspecific
    • interspecific
    • Scramble competition, contest competition, emigration

  17. There are three major types of spatial distributions
    • Clumped
    • Uniform
    • Random
  18. clumped distribution
    • Populations who live in groups exhibit clumped distribution
    • Examples include elephant herds, wolf packs, prides of lions, flocks of birds, and schools of fish
    • Advantages of clumped distributions include:
    • Many eyes that can search for localized food sources
    • Movement of the group (e.g., schools of fish or flocks of birds) can confuse predators by their sheer numbers
    • Predators, in turn, may hunt in groups, cooperating to bring down larger prey

  19. Advantages of clumped distributions include:
    • Many eyes that can search for localized food sources
    • Movement of the group (e.g., schools of fish or flocks of birds) can confuse predators by their sheer numbers
    • Predators, in turn, may hunt in groups, cooperating to bring down larger prey

  20. Survivorship in populations follows three basic patterns
    • Late-loss populations
    • Constant-loss populations
    • Early-loss populations
  21. Late-loss populations
    • Late-loss populations produce convex survivorship curves
    • Examples include humans and many large mammals, such as elephants and mountain sheep
  22. Constant-loss populations
    • Constant-loss populations produce relatively straight lines
    • Examples include some bird species, such as gulls and the American robin
  23. Early-loss populations
    • Early-loss populations produce concave survivorship curves
    • Examples include most invertebrates, most plants, and many fish

  24. Demography
    • Demography is the study of the changing human population
    • Demographic data are used to formulate policies in:
    • public health,
    • housing,
    • education,
    • employment,
    • immigration, and
    • environmental protection

  25. A series of advances have increased Earths carrying capacity to support people-such as…?
    • Technical advances
    • agricultural advances
    • industrial and medical advances
  26. Technical advances
    • Technical advances: Early humans discovered fire, invented tools and weapons, built shelters, and designed protective clothing
  27. Agricultural advances
    • Agricultural advances: Around 8000 B.C., animals and plants were domesticated, providing a larger and more stable food supply .This resulted in a longer life span and more childbearing years, although disease continued to restrain population growth
  28. Industrial and medical advances
    • Industrial and medical advances: Beginning in England in the mid-eighteenth century, medical and industrial advances permitted a population explosion. Industrial advances allowed fewer people to produce more food.Medical advances decreased the death rate from infectious disease
  29. population stages
    • pre industrial stage
    • Transitional stage
    • Industrial stage
    • Post Industrial stage
  30. Pre-industrial stage
    • Pre-industrial stage: The population was relatively small and stable, with high birth rates and high death rates
  31. Transitional stage
    • Transitional stage: Food production increased and health care improved, which caused death rates to fall; because birth rates remained high, there was an explosive population increase
  32. Industrial stage:
    • Industrial stage: Birth rates fell as contraceptives were more available, and as people moved from farms to cities, where children were less important as a source of labor
  33. Post-industrial stage
    • Post-industrial stage: Populations are relatively stable, with low birth and death rates

  34. replacement-level fertility (RLF)
    • A population will eventually stabilize if parents have just the number of children to replace themselves, called replacement-level fertility (RLF)

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