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Population Ecology

Explore how human population is controlled, analyzing demographic factors, growth rates, carrying capacity, limiting factors, and human impact on ecological balance. Learn about population growth curves, limiting factors affecting population size, and the unique challenges in human population control compared to other species.

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Population Ecology

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  1. Population Ecology Warm-up Question: If humans have no natural predators, how is our population controlled? Provide examples.

  2. Key Terms • Demography- study of human populations • Density- number of individuals per unit area • Dispersion- relative arrangement of individuals within a given amount of space

  3. Population Density of U.S.

  4. Dispersion ‪www.eoearth.org

  5. Growth Rates • Growth Rate: change in population over time • Positive (+): birth rate > death rate • Zero (0): birth rate = death rate • Negative (-) = birth rate < death rate • Fertility Rate: The average number of offspring a female has in its lifetime • Replacement Rate: each mating couple has two offspring that survive to reproduce, replacing parents (fertility rate = 2.1)

  6. Reproductive Potential • Maximum number of offspring each member of a population can produce • Increases when members reproduce often and earlier in their reproductive life • Generation time- time it takes for an average member of a population to reproduce. • Human Generation time: 20 years • E.Coli Generation time: 17 minutes

  7. Population Growth Curves

  8. Exponential Growth • Increase in population size due to a constant growth rate • Unlimited resources • Ideal conditions • “J” curve

  9. Logistic Growth • Population growth slows or stops following a period of exponential growth • Birth rate decreases, Death rate increases OR Both • “S curve”

  10. Carrying Capacity (K) • The maximum amount of individuals an environment can support • What happens to growth rate as it approaches K?

  11. Reaching Carrying Capacity www.algebralab.org

  12. Logistic Growth- “Overshoot” Population grows beyond carrying capacity and collapses Carrying Capacity is often diminished due to overshoot rewild.info

  13. Limiting Factors Pair and Share (2 min): • What factors would cause a population’s size to increase? • What factors would cause a population’s size to decrease?

  14. Limiting Factors • Food • Water • Sunlight (producers) • Space • Disease • Competition

  15. Limiting Populations Density-Dependent Density-Independent Size of population does not matter; Deaths occur independently of population density Ex: natural disasters • Deaths occur more quickly in a more crowded environment • Limited resources • Disease

  16. Human Carrying Capacity? • Current human population: 7.12 billion people • Ranges estimated from 4-16 billion people • Hard to estimate how many people this world can hold • Technological innovations • Medical breakthroughs • http://www.census.gov/popclock/

  17. What caused this rapid growth?

  18. What sparked our growth? • Industrial Revolution (~1750) • Modern medicine (20th century) • Death rates DROPPED due to better care • Agricultural Advances • Transportation Advances

  19. Human Population Growth Source: U.S. Census Bureau- World POPclock Projection

  20. What takes us out? Humans are at the top of any food web resulting in no natural predators to keep our populations in check… • What are the limiting factors of the human population? • How are we different than other species in regards to population control?

  21. What’s our limiting factor? • Disease: Bubonic Plague, AIDS, Flu, Malaria • Access to food • Access to clean water • Competition (a.k.a. War)

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