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Population Ecology

Population Ecology. Warm-up Question : If humans have no natural predators, how is our population controlled? Provide examples. . Key Terms. Demography- study of human populations Density- number of individuals per unit area

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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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