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POPULATIONS

POPULATIONS. 3 Characteristics of populations. Geographic (Spatial) Distribution Density Growth Rate. Geographic (SPATIAL) Distribution. Dispersion – the pattern of spacing of a population within an area 3 types Uniform Clumped Random. Uniform Distribution.

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POPULATIONS

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  1. POPULATIONS

  2. 3 Characteristics of populations • Geographic (Spatial) Distribution • Density • Growth Rate

  3. Geographic (SPATIAL) Distribution • Dispersion – the pattern of spacing of a population within an area • 3 types • Uniform • Clumped • Random

  4. Uniform Distribution • Population is spread out evenly

  5. Clumped Distribution • Populations gather in clumps

  6. Random Distribution • Populations spread out randomly, forming clumps in some areas and uniformity in others

  7. Density • The number of organisms per unit area • Low density vs. High density

  8. Growth Rate • How fast does a given population grow? • 2 main types • Exponential Growth • Logistic Growth

  9. Exponential Growth • Occurs when the individuals in a population reproduce at a constant rate • The increase is slow at first. This is called the Lag Phase. • Over time the population becomes larger. This is called the exponential growth phase. • Under ideal conditions with unlimited resources, a population will grow exponentially

  10. What does it look like? A.K.A. J- curve Lag Phase

  11. Logistics • When a population’s growth slows or stops following a period of exponential growth • Limited by availability of resources • Population growth may slow down when: • The death rate increases • The birthrate decreases • When resources (food, shelter, optimal temperature) are not available • When the carrying capacity is reached. • Carrying Capacity – the maximum number of organisms that can be supported by a given environment

  12. What does it look like? Carrying capacity A.K.A. S-curve

  13. Factors that affect the population size • Number of Births • Number of Deaths • Number of Individuals that enter or leave a population

  14. Limiting Factors • Factors that cause population growth to decrease • Can be Density Dependent – depends on the # of organisms • Can be Density Independent – does not depend on the # of organisms

  15. DDF: Competition • Crowded populations compete for food, shelter, water, sunlight • The more individuals in a given area, the sooner they will use up the available resources • Occurs between same species and also members of different species • Both species are under pressure to change (evolution) to occupy the separate niches • No two species can occupy the same niche, this is called competitive exclusion

  16. DDF: Predation • There are always more prey than predators • When this balance shifts, then competition for prey will result • Starvation may also be the result if prey is not available

  17. DDF: Parasitism and Disease • Parasites range in size from microscopic, disease causing bacteria to tapeworm 30 cm or more in length • They take nourishment at the expense of their hosts, often weakening them and causing disease and death

  18. Density Independent Factors • Unusual weather (storms or hurricanes) • Natural Disasters (earthquakes, volcanic eruptions) • Seasonal Cycles (Extreme hot or cold weather) • Human Activities (Damming rivers, clear-cutting forests, industrialization, hunting, fishing)

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