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POPULATIONS

POPULATIONS. Definition: All the members of a species that live in one place at one time. PROPERTIES of Populations. Population SIZE The number of individuals in a population Population DENSITY Number of individuals per unit of area DISPERSION

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POPULATIONS

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  1. POPULATIONS Definition: All the members of a species that live in one place at one time.

  2. PROPERTIES of Populations • Population SIZE • The number of individuals in a population • Population DENSITY • Number of individuals per unit of area • DISPERSION • SPATIAL distribution of individuals within the population • Uniform • Random • Clumped

  3. PROPERTIES of Populations

  4. Population Growth RATE Definition • The amount by which a population’s sizechanges over time.

  5. Population Growth RATE • Depends on: • Birth • Death • Emigration: movement of individuals OUT OF a population • Immigration: movement of individuals INTO a population + - - +

  6. 2 Types of Population Growth • Exponential • Logistic

  7. EXPONENTIAL Model of Population Growth • Population increases rapidly with no limit • What will a graph look like? • Rare in nature. Why? “J” shaped curve Limit on the amount of resources (food / space)

  8. LOGISTIC Model of Population Growth As population reaches carrying capacity, death rate increases • Accounts for influence of limiting factors (like food, space) • What will the graph look like? When at carrying capacity, birth rate is equal to death rate When population is small, birth rate is higher than death rate Stretched out “S”

  9. Population Growth Limited by Carrying Capacity Definition: The number of individuals the environment can support over a long period of time

  10. Population Size REGULATION 1. Density Independent Factors: reduce population regardless of population size Examples: • Weather • Fires • Floods

  11. Population Size REGULATION 2. Density Dependent Factors: triggered by increasing population density Examples • Food shortages • Space limitations • Waste accumulation

  12. Example of Exponential Growth Phase (J-Shaped Curve) • Ex. Human Population • Human population increased relatively slowly until about 1650. • It then doubled in the next two centuries • It doubled again in the next 80 years. • Our population is now about 7 billion. • This increases by 80 million/year • This in an increase of 220,980/day. • It takes 3 years for the world population to add the population equivalent of another US.

  13. Example of Exponential Growth Phase (J-Shaped Curve)

  14. Example of Exponential Growth Phase (J-Shaped Curve) • How long will it be until we reach our carrying capacity? What will happen then? • What factors increase our carrying capacity? • Farming • Medicines • Better sanitation

  15. Example of Exponential Growth Phase (J-Shaped Curve) • What impact does this stretching our carrying capacity have on other species. • Endangers them or completely wipes them out.

  16. Example of Exponential Growth Phase (J-Shaped Curve) • What are some consequences of human population growth? • Global Warming • Caused by the increasing burning of fossil fuels which lead to the greenhouse effect. • Pollution • Acid Rain • Pile up of Waste • Ozone Depletion

  17. The End!!

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