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Chapter 5: Population Ecology

Chapter 5: Population Ecology. Population. 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 examined in multiple ways Populations can increase , decrease , or stay the same over time.

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Chapter 5: Population Ecology

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  1. Chapter 5: Population Ecology

  2. Population • 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 examined in multiple ways • Populations can increase, decrease,or stay thesameover time

  3. Properties of Populations • Population Size • A population’s size is the number of individuals that the population contains. • Population Density • Density is a measure of how crowded the population is. • Age Structure • A population’s agestructureindicates the percentage of individuals at each age.

  4. Properties of Populations, cont. • Dispersion • Dispersion describes the distribution of individuals within the population and may be random, uniform, or clumped.

  5. THINK What do you think might affect a population’s growth and size?

  6. Key Point: A limiting factoris somethingthat keeps a population from growing infinitely Think: What are the 5 major limiting factors? Resources, Space, Predators, Disease, and Habitat There are 2 different types of limiting factors

  7. 1. Density-Independent Factors Key Point: Density-independent factors are not affected by the population size Do not depend on the number of individuals present in an area. Examples: Unusual weather, natural disasters, and seasonal cycles

  8. 2. Density-Dependent Factors • Key Point: Population-limiting factors, such as competition, are density-dependentbecause the effect on each individual dependsonthe number of other individuals present in the same area. Examples: Competition, disease, and predation

  9. You Try: Density-Dependent or Independent?

  10. Predation

  11. Weather Patterns

  12. Disease

  13. Competition for Resources

  14. Survivorship Curves • Patterns of Mortality • Populations show three patterns of mortality or survivorshipcurves: • 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)

  15. Survivorship Curves, cont. • Type I = large mammals (i.e., humans, elephants) • Type II = birds, lizards, rodents • Type III = fish, insects

  16. Population Growth Rate • Scientists define the growthrateof a population as the amount by which a population’s size changes in a given time. • Population Size • Birth rate - death rate = growth rate If the birth rate increases, the population increases If the death rate increases, the population decreases

  17. Exponential Growth • The exponentialmodeldescribes perpetual growth at a steady rate in a population • The model assumes constant birth and death rates • Assumes unlimited resources

  18. Logistic Growth • In the logisticmodel, birth rates fall and death rates climb as the population grows & resources are consumed • When the carryingcapacity is reached, the number of individuals the environment can support is reached and population growth becomes stable

  19. You Try: Exponential or Logistic?

  20. You Try: Exponential or Logistic?

  21. You Try: Exponential or Logistic?

  22. 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 • 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

  23. Human Population Growth • Population Growth Today • Today, developing countries have faster human population growth and lower standards of living than developed countries do • Although the overall growth rate has slowed, the world’s population is still increasing

  24. Human Population Growth • Demographic Transition • Demography: The scientific study of human populations and how they change over time • Human populations have undergone rapid growth, yet in some developed countries, populations have stopped growing. • The demographic transition model help explains how these population changes happen

  25. Demographic Transition Model

  26. Age Structure

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