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Chapter 5

Chapter 5. Biodiversity, Species Interactions, and Population Control. They were over-hunted to the brink of extinction by the early 1900’s and are now making a comeback. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?. Figure 5-1.

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Chapter 5

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  1. Chapter 5 Biodiversity, Species Interactions, and Population Control

  2. They were over-hunted to the brink of extinction by the early 1900’s and are now making a comeback. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Figure 5-1

  3. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Sea otters are an important keystone species for sea urchins and other kelp-eating organisms. Figure 5-1

  4. Characteristics of Population Population dynamics Population size Population density Carrying Capacity

  5. Exponential and Logistic Growth K Population size (N) Population size (N) Time (t) Time (t) Exponential Growth Logistic Growth Year Year

  6. Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size Members of populations which exceed their resources will die unless they adapt or move to an area with more resources. Figure 5-13

  7. Chapter 6 The Human Population and Its Impact

  8. Core Case Study: Is the World Overpopulated? The world’s population is projected to increase from 6.6 billion to 9.3 billion between 2006 and 2050. The debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science.

  9. Core Case Study: Is the World Overpopulated? Some argue that the planet has too many people. Some feel that the world can support billions of more people due to technological advances. There is a constant debate over the need to reduce population growth. Must consider moral, religious, and personal freedom.

  10. Factors Affecting Death Rates Death rates have declined because of: Increased food supplies, better nutrition. Advances in medicine. Improved sanitation and personal hygiene. Safer water supplies. U.S. infant mortality is higher than it could be due to: Inadequate pre- and post-natal care for poor. Drug addiction. High teenage birth rate.

  11. Where Are We Headed? U.N. world population projection based on women having an average of 2.5 (high), 2.0 (medium), or 1.5 (low) children. Figure 6-2

  12. Factors Affecting Human Population Size Population Change = (Births + Immigration) – (Deaths + Emigration) • Population change equation • Zero population growth (ZPG)

  13. Core Case Study: Is the World Overpopulated? Much of the world’s population growth occurs in developing countries like China and India. TFR (total fertility rate) highest in Africa. 5+ Figure 6-1

  14. Case Study: Slowing Population Growth in China- 1 child policy Generally positive results: • Economic incentives • Free medical care • Preferential treatment • Intrusive and coercive

  15. Case Study: Slowing Population Growth in Thailand Generally positive results: • 3.2% growth, 6 child family • Woman literacy, economic role • Religion support- Buddhist • openmindness

  16. Case Study: Slowing Population Growth in India Generally disappointing results: • Bureaucratic inefficiency • Low status of women • Lack of support

  17. Some Problems with Rapid Population Decline (Japan) . Figure 9-12

  18. Solutions: Influencing Population Size • Migration Pension plans • Family planning • Empowerment of women • Economic rewards and penalties

  19. Birth Rates in the U.S. from 1910 to 2008 6-5

  20. POPULATION AGE STRUCTURE Populations with a large proportion of its people in the preproductive ages 1-14 have a large potential for rapid population growth. Figure 6-8

  21. POPULATION AGE STRUCTURE The number of people in young, middle, and older age groups determines how fast populations grow or decline. The number of people younger than age 15 is the major factor determining a country’s population growth. Changes in the distribution of a country’s age groups have long-lasting economic and social impacts.

  22. POPULATION AGE STRUCTURE About 14% of the world’s population live in countries with stabilizing or declining populations. Rapid population decline can lead to long-lasting economic and social problems. Death from AIDS can disrupt a country’s social and economic structure by removing significant numbers of young adults.

  23. SOLUTIONS: INFLUENCING POPULATION SIZE Demographic Transition: As countries become economically developed, their birth and death rates tend to decline. Preindustrial stage: little population growth due to high infant mortality. Transitional stage: industrialization begins, death rates drops and birth rates remain high. Industrial stage: birth rate drops and approaches death rate. Post-Industrial: Population levels off and declines

  24. SOLUTIONS: INFLUENCING POPULATION SIZE Generalized model of demographic transition. Some developing countries may have difficulty making the demographic transition. Figure 6-12

  25. Lester Brown Our numbers expand but Earth’s natural systems do not. End chapter 5 &6

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