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Chapter 5- Populations

Chapter 5- Populations. How many people are in the world?. 6.7 Billion. Population Density of the World. World Population over Time. Important Characteristics . Geographic distribution Density Growth Rate. Important Characteristics . Geographic distribution- area that is inhabited

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Chapter 5- Populations

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  1. Chapter 5- Populations

  2. How many people are in the world? • 6.7 Billion

  3. Population Density of the World

  4. World Population over Time

  5. Important Characteristics • Geographic distribution • Density • Growth Rate

  6. Important Characteristics • Geographic distribution- area that is inhabited • Density • Growth Rate

  7. Important Characteristics • Geographic distribution • Density- number of individuals per unit area • Growth Rate

  8. Important Characteristics • Geographic distribution • Density- number of individuals per unit area • Growth Rate

  9. Important Characteristics • Geographic distribution • Density • Growth Rate- how fast the population grows

  10. Growth Rates Population size is determined by • Number of births • Number of deaths • Number of individuals that enter or leave the population

  11. Growth Rates • Birth rate- how many are born • Baby Boom • Death rate- how many die • Black Plague

  12. Growth Rates Birth Rate Death Rate Overall Rate

  13. Growth Rates • Immigration- movement into area • Emigration- movement out of area • What causes people to immigrate or emigrate? • What causes bears to immigrate or emigrate?

  14. Growth rates? • Where are the high birth rates in the world? • Where are the high death rates in the world? • Many developed nations have a negative growth rate. Why?

  15. What limits a population’s growth? -ability to reproduce quickly -nutrients -space -water

  16. Growth limiting factors Bacteria- divide every 20 minutes one day- 4,720,000,000,000,000,000,000 What is the reproduction rate for a mouse? What is the reproduction rate for a human?

  17. Exponential Growth When a population reproduces at a constant rate. This occurs only under ideal conditions with unlimited resources.

  18. Logistic growth Logistic growth- occurs when a population’s growth slows or stops after exponential growth Why does a population stop growing exponentially? • Birth rate decreases • Death rate increases • Immigration decreases • Emigration increases

  19. Carrying capacity Carrying capacity- The largest number of individuals that an environment can support

  20. Limits to growth Limiting factor- a factor that causes population growth to decrease Competition Predation Parasitism and disease Human disturbances Drought and other climate extremes

  21. Density-dependent limiting factor • Density-dependent limiting factor- depends on the population size • Competition- food, water, space, sunlight • Same species • Different species • Competitive exclusion principle • No two species can occupy the same niche in the same habitat at the same time

  22. Density-dependent limiting factor • Predation predator-prey relationship Parasitism and Disease

  23. Density-Independent Factors Density-Independent Factors- affect all populations, regardless of size Unusual weather Natural disasters Seasonal cycles Human activities- damming rivers and clear-cutting forests

  24. Human Population Growth Demography- the scientific study of human populations Demographic transition- a dramatic change in birth and death rates

  25. Demographic transition • 1. Birth rates stay same, Death rates decline • 2. Birth rates decline, death rates stay low Birth Rate Death Rate Overall Rate Birth Rate Death Rate Overall Rate

  26. Age Structure • Age-Structure Diagram- graph of the numbers of people in different age groups

  27. Future Population Growth • How many people can the world support? • What are the things that people need to live? • -food • -water • -housing • -jobs

  28. Future Population Growth Resources vs. Population

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