Chapter 8 Population Change - PowerPoint PPT Presentation

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Chapter 8 Population Change

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  1. Chapter 8Population Change

  2. Overview of Chapter 8 • Principles of Population Ecology • Reproductive Strategies • The Human Population • Demographics of Countries • Demographics of United States

  3. Principles of Population Ecology • Population Ecology • Study of populations and why their numbers change over time • Important for • Endangered species • Invasive species • Population • Group of individuals of same species living in the same geographic area at the same time

  4. Population Density • Population density • The number of individuals of a species per unit area or volume at a given time • Ex: minnows per Liter of pond water • Ovals below have same population, and different densities

  5. Change in Population Size

  6. Change in Population Size

  7. Death rate Growth rate Emigration rate Birth rate Immigration rate Calculating Population Change Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people r = (b – d) + (i – e)

  8. Maximum Population Growth • Intrinsic Rate of Growth (Biotic Potential) • Growth rate under ideal conditions • J- Shaped Curve (exponential growth)

  9. Environmental Resistance • Environmental limits (resistance) • Prevent indefinite reproduction • Unfavorable food, water, shelter, predation, etc. • Carrying Capacity (K) • Maximum # of individuals an environment can support • Causes leveling off of exponential growth • S- shaped curve of logistic population growth

  10. Population Crash • Overshooting carrying capacity can lead to population crash • Abrupt decline in population density

  11. Factors That Affect Population Size • Density Dependent Factor • Factor whose effect on population changes as population density changes • Examples: • Predation • Disease • Competition • Sometimes cause Boom-or-Bust Population Cycles

  12. Boom-Or-Bust Population Cycles

  13. Case Study- Predator Prey Dynamics on Isle Royale • As wolf population increases, moose population decreases (and vice versa)

  14. Factors That Affect Population Size • Density Independent Factors • Factors that affects population size, but is not influenced by changes in population density • Examples: • Killing frost • Severe blizzard • Fire

  15. Reproductive Strategies

  16. Survivorship

  17. Some populations fit two curves • Herring Gulls • Type III & Type II

  18. Human Population • Demography • Science of population structure and growth • Human Population since 1980 is J-shaped curve

  19. Human Population

  20. Population Increase in Mexico

  21. Projecting Future Populations • Population is increasing • Growth rate (r) has started to decline • Projections for 2050 • Low = 7.7 billion • High = 10.6 billion • Most likely = 9.1 billion

  22. Demographics of Countries

  23. Demographic Stages • Pre-industrial Stage • Birth and death rates high • Modest population growth • Transitional Stage • Lowered death rate • Rapid population growth • Industrial Stage • Birth rate decline • Population growth slow • Post Industrial Stage • Low birth and death rates • Population growth very slow

  24. Demographic Stages

  25. Age Structure • The number and proportion of people at each age in a population

  26. Demographics of Specific Countries

  27. World-wide • 29% of human population is under age 15 • Could cause large increase in birth rates

  28. Education of Immigrants into USThe Role of Education in Society