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Chapter 51

Chapter 51. Introduction to Ecology: Population Ecology. Population density Number of individuals of a species per unit at a given time Population dispersion (spacing) Clumped dispersion Uniform dispersion Random dispersion. Dispersion of individuals with a population.

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Chapter 51

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  1. Chapter 51 Introduction to Ecology: Population Ecology

  2. Population density • Number of individuals of a species per unit at a given time • Population dispersion (spacing) • Clumped dispersion • Uniform dispersion • Random dispersion

  3. Dispersion of individuals with a population

  4. Dispersion in a sand pine population in Florida

  5. Four factors that produce changes in population size • Natality • Mortality • Immigration • Emigration

  6. Intrinsic rate of increase (rmax) • Maximum rate at which species or population can increase under ideal conditions • Carrying capacity (K) is the largest population that can be maintained • Exponential population growth (J-shaped curve) • Logistic population curve (S-shaped curve)

  7. Exponential population growth

  8. Carrying capacity and logistic population growth

  9. Density-dependent factors • Regulate population growth by affecting a large proportion of the population as population rises • Examples include predation, disease, and competition

  10. Density-dependent factors and negative feedback

  11. Density-independent factors • Limit population growth but are not influenced by changes in population density • Examples include hurricanes and blizzards

  12. Semelparous reproduction • Expend their energy in a single, immense reproductive effort • Iteroparous reproduction • Exhibit repeated reproductive cycles throughout their lifetimes

  13. Semelparity

  14. Species exhibiting an r strategy • Emphasizes a high growth rate • Organisms typically have small body size, high reproductive rates, short life spans, and they inhabit variable environments

  15. Species exhibiting a K strategy • Maintains a population near the carrying capacity of the environment • Species often have large body size, low reproductive rates, long life spans, and they inhabit stable environments

  16. Survivorship curves • Type I • Mortality is greatest in old age • Type II • Mortality is spread evenly across all ages • Type III • Mortality is greatest among the young

  17. Survivorship curves

  18. Survivorshipcurve for a herring gull population

  19. Source habitats • Preferred habitats • Local reproductive success is greater than local mortality • Local individuals disperse from source habitats

  20. Sink habitats • Lower-quality habitats • Individuals may suffer death or poor reproductive success

  21. Source and sink populations in a hypothetical metapopulation

  22. Human population growth • World population reached 6.3 billion in 2003 • Per capita growth rate has declined from peak in 1965 of about 2% per year to 1.3% • Scientists predict zero population growth by the end of the 21st century

  23. Human population growth

  24. Population characteristics • Highly developed countries • Low birth rate, low infant mortality, low fertility rate, long life expectancies, and high GNI PPP • Developing countries • High birth rate, high infant mortality, high fertility rate, short life expectancies, and low GNI PPP

  25. Comparison of 2003 population data in developed and developing countries

  26. Birth and death rates in Mexico, 1900–2000

  27. Age structure influences dynamics • Possible for country to have replacement-level fertility and still experience population growth • Young age structure causes a positive population growth momentum as large prereproductive age group matures

  28. Age structure diagrams

  29. Developing countries tend to have people overpopulation that degrades the environment • Developed countries have consumption overpopulation that degrades the environment

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