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Population Ecology

This article explores the concepts of population ecology, focusing on population density, dispersion patterns, and factors influencing population size, including natality, mortality, immigration, and emigration. It discusses clumped, uniform, and random dispersion, emphasizing the effects of density-dependent and density-independent factors. Human population growth trends are analyzed, with a comparison between developed and developing countries. The implications of age structure on population momentum and the relationship between population dynamics and environmental degradation are also highlighted.

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Population Ecology

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  1. Population Ecology

  2. Population DensityNumber 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: Birth Rate • Mortality: Death Rate • Immigration: Entering a territory • Emigration: Leaving a territory

  6. 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 population growth

  9. Density-dependent factors: • Factors that 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: • Factors that limit population growth but are not influenced by changes in population density • Examples include hurricanes, blizzards, floods, volcanic eruptions, drought, etc

  12. Human Population Growth • World population reached 6.3 billion in 2003. Today is almost 7.0 billion • 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

  13. Human population growth

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

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

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

  17. Age structure influences dynamics • Young age structure causes a positive population growth momentum as large pre-reproductive age group matures

  18. Age structure diagrams

  19. Developing countries tend to have over-population which degrades the environment. (Mexico, Brazil, India, China etc) • Developed countries tend to have over-consumption which degrades the environment. (USA, Germany, France, Britain, etc)

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