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Population Ecology

Population Ecology. Chapter 19. Properties of Populations. What is a population? Group of organisms that belong to the same species and live in a particular place at the same time. What classifies a group to be considered a population? Population Size -- # of individuals

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Population Ecology

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  1. Population Ecology Chapter 19

  2. Properties of Populations • What is a population? • Group of organisms that belong to the same species and live in a particular place at the same time. • What classifies a group to be considered a population? • Population Size -- # of individuals • Population Density – how crowded is it • Dispersion (clumped, even or uniform, random)

  3. Also known as even dispersion.

  4. Population Dynamics • Populations are dynamic…meaning they change in size and composition over time. • Birth Rate • Death Rate (Mortality) • Life Expectancy • Age Structure – distribution of individuals among different ages in a population. • Survivorship Curves – mortality rate data of different species tend to conform to 1 of 3 curves.

  5. AGE STRUCTURE GRAPHS

  6. SURVIVORSHIP CURVES Type I = Likelihood of dying is small until late in life Type II = Some species the probability of dying doesn’t change throughout life Type III = Many organisms are very likely to die when young

  7. Measuring Populations (Ch. 19-2) • Demographers study population dynamics. • The size of a population depends on four factors: birth, death, emigration, and immigration. 1. Emigration- movement of individuals out of a population. • Immigration- movement of individuals into a population. Growth rate = birth rate – death rate

  8. Population Growth Type 1 • Exponential Growth…”J” shaped curve. • The larger the population gets, the faster it grows.

  9. Limits on Populations • A limiting factor is an environmental factor that prevents or stops a population from growing. • What would be some examples of limiting factors?

  10. Answers • Some limiting factors --- natural disasters, weather, disease, living space, competition, predation, etc.

  11. Logistic Growth…”S” shaped curve. Builds on the exponential model but takes into account limiting factors. Carrying Capacity- number of individuals the environment can support over a long period of time. Population Growth Type 2

  12. Population Regulation • Density Dependent --- A factor that has an increasing affect as a population increases. Examples --- disease, competition, parasites, and food. • Density Independent --- affects all populations no matter what their size or density is. Examples – temperature, floods, storms, drought, and habitat destruction.

  13. Human Population Growth(Ch. 19-3) • The history…hunter-gathers (500,000 years ago). Growth of population was very slow due to small populations and a high mortality rate. • Agricultural Revolution (10,000 years ago). Population began to grow fast because of increased food supply. • Bubonic Plague (1347-1352)…wiped out 25% of Europe’s population. • 1650…Why did mortality rates decrease? • World War II

  14. Population Growth Today • It took most of human history for the world’s population to reach 1 billion (Year 1800) • It took 27 years for the population to grow from 3 billion to 5 billion (1960-1987). • 20% of the world’s population lives in developed countries. (includes modern, industrialized countries) • 80% lives in developing countries. (poorer countries & populations growing faster.)

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