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Populations

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  • 1. Table of Contents
    • Section 1 Understanding Populations
    • Section 2 Measuring Populations
    • Section 3 Human Population Growth
    Populations
  • 2. Objectives
    • Describe the main properties that scientists measure when they study populations.
    • Compare the three general patterns of population dispersion.
    • Identify the measurements used to describe changing populations.
    • Compare the three general types of survivorship curves.
    Section 1 Understanding Populations
  • 3. Properties of Populations
    • A population is a group of organisms that belong to the same species and live in a particular place at the same time.
    • Populations can be measured in terms of size, density, dispersion, growth rate, age structure, and survivorship.
    Section 1 Understanding Populations
  • 4. Population Click below to watch the Visual Concept. Visual Concept Section 1 Understanding Populations
  • 5. Properties of Populations, continued
    • Population Size
      • A population’s size is the number of individuals that the population contains.
    Section 1 Understanding Populations
  • 6. Properties of Populations, continued
    • Population Density
      • Density is a measure of how crowded the population is.
    Section 1 Understanding Populations
  • 7. Properties of Populations, continued
    • Dispersion
      • Dispersion describes the distribution of individuals within the population and may be random, uniform, or clumped.
    Section 1 Understanding Populations
  • 8. Three Patterns of Population Dispersion Section 1 Understanding Populations
  • 9. Characteristics of Populations Click below to watch the Visual Concept. Visual Concept Section 1 Understanding Populations
  • 10. Population Dynamics
    • Age Structure
      • A population’s age structure indicates the percentage of individuals at each age.
    Section 1 Understanding Populations
  • 11. Population Dynamics, continued
    • Patterns of Mortality
      • Populations show three patterns of mortality or survivorship curves :
        • Type I (low mortality until late in life)
        • Type II (constant mortality throughout life)
        • Type III (high mortality early in life followed by low mortality for the remaining life span).
    Section 1 Understanding Populations
  • 12. Survivorship Curves Section 1 Understanding Populations
  • 13. Objectives
    • Identify the four processes that determine population growth.
    • Compare the exponential model and the logistic model of population growth.
    • Differentiate between density-dependent and density-independent regulation of populations.
    • Explain why small populations are more vulnerable to extinction.
    Section 2 Measuring Populations
  • 14. Population Growth Rate
    • Demographers, scientists who study population dynamics, define the growth rate of a population as the amount by which a population’s size changes in a given time.
    Section 2 Measuring Populations
  • 15. Population Growth Rate, continued
    • Population Size
      • Birth rate - death rate = growth rate
    Section 2 Measuring Populations
  • 16. The Exponential Model
    • The exponential model describes perpetual growth at a steady rate in a population.
    • The model assumes constant birth and death rates and no immigration or emigration.
    Section 2 Measuring Populations
  • 17. Exponential Growth Click below to watch the Visual Concept. Visual Concept Section 2 Measuring Populations
  • 18. The Logistic Model
    • In the logistic model, birth rates fall and death rates climb as the population grows.
    • When the carrying capacity is reached, the number of individuals the environment can support is reached and population growth becomes stable.
    Section 2 Measuring Populations
  • 19. Logistic Model Click below to watch the Visual Concept. Section 2 Measuring Populations Visual Concept
  • 20. Two Population Growth Models Section 2 Measuring Populations
  • 21. Population Regulation
    • Population-limiting factors, such as competition, are density-dependent because the effect on each individual depends on the number of other individuals present in the same area.
    Section 2 Measuring Populations
  • 22. Population Regulation, continued
    • Population-limiting factors, such as bad weather and fires, are density-independent because the effect on each individual does not depend on the number of other individuals present in the same area.
    Section 2 Measuring Populations
  • 23. Comparing Density-Dependent and Density-Independent Factors Click below to watch the Visual Concept. Visual Concept Section 2 Measuring Populations
  • 24. Population Regulation, continued
    • Population Fluctuations
      • All populations fluctuate in size.
    Section 2 Measuring Populations
  • 25. Population Regulation, continued
    • Perils of Small Populations
      • Small populations have low genetic diversity and are subject to inbreeding, so they are less likely to adapt to environmental changes.
    Section 2 Measuring Populations
  • 26. Objectives
    • Explain how the development of agriculture changed the pattern of human population growth.
    • Describe changes in human population size in the past 10,000 years.
    • Compare observed patterns of population growth in developed and developing countries.
    Section 3 Human Population Growth
  • 27. History of Human Population Growth
    • The Development of Agriculture
      • About 10,000 to 12,000 years ago, the development of agriculture increased the growth rate of the human population.
    Section 3 Human Population Growth
  • 28. History of Human Population Growth, continued
    • The Population Explosion
      • Around 1650, improvements in hygiene, diet, and economic conditions further accelerated population growth.
      • After World War II, the human population grew at the fastest rate in history, largely because of better sanitation and medical care in poorer countries.
    Section 3 Human Population Growth
  • 29. History of Human Population Growth, continued
    • Population Growth Today
      • Today, developing countries have faster human population growth and lower standards of living than developed countries do.
    Section 3 Human Population Growth
  • 30. Human Population Growth Section 3 Human Population Growth
  • 31. Demographic Transition
    • Human populations have undergone rapid growth, yet in some developed countries, populations have stopped growing.
    • The demographic transition model shows how these population changes happen.
    Section 3 Human Population Growth
  • 32. Demographic Transition Model Section 3 Human Population Growth