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  1. 1. Populations
  2. 2. Remember… <ul><li>Population – all the members of the same species living in the same place </li></ul><ul><li>A population is usually a reproductive group – members of one population only breed with members of the same population </li></ul><ul><ul><li>Ex. Palm trees in Hawaii don’t breed with palm trees in Florida </li></ul></ul>
  3. 3. Three ways to describe a population… <ul><li>Size </li></ul><ul><ul><li>Number of individuals in a population </li></ul></ul><ul><ul><li>Ex. Number of bass in a lake </li></ul></ul><ul><li>Density </li></ul><ul><li>Number of individuals per unit area or volume </li></ul><ul><ul><li>Ex. The number of bass per cubic meter in a lake </li></ul></ul>
  4. 4. 3) Dispersion <ul><li>The relative distribution or arrangement of animals in a given amount of space </li></ul><ul><ul><li>Even/Uniform </li></ul></ul><ul><ul><li>Clumped </li></ul></ul><ul><ul><li>Random </li></ul></ul>
  5. 5. Population Growth is affected by: <ul><li>Number of births </li></ul><ul><li>Number of deaths </li></ul><ul><li>Number of individuals that enter or leave </li></ul><ul><ul><li>Immigration </li></ul></ul><ul><ul><li>Emigration </li></ul></ul>Growth = Number of Births + Number Immigrated – Number of Deaths – Number Emigrated
  6. 6. <ul><li>Immigration - movement of individuals into an area. (causes growth) </li></ul><ul><li>Emigration – movement of ind. out of a population. (causes pop. to decrease) </li></ul><ul><li>Think “exit” for Emigration! </li></ul>Growth = Number of Births + Number Immigrated – Number of Deaths – Number Emigrated
  7. 7. Growth Rate = Change in Population Time **Growth Rates can be positive, negative, or zero
  8. 8. Population Growth <ul><li>Reproductive Potential – the maximum number of offspring each member of a population can produce </li></ul><ul><li>Reproductive potential increases when individuals produce more offspring at a time, reproduce more often, and reproduce earlier in life </li></ul>
  9. 9. Population Growth <ul><li>Exponential growth </li></ul><ul><ul><li>Individuals reproduce at a constant rate </li></ul></ul><ul><ul><li>Occurs in nature only when populations have plenty of food and space and little or no competition or predators </li></ul></ul>
  10. 10. What limits population growth? <ul><li>Logistic Growth </li></ul><ul><ul><li>When a populations growth slows or stops as the population reaches the carrying capacity. </li></ul></ul>Carrying Capacity - The largest number of individuals that the environment can support. As resources are used up, or the environment changes, deaths increase, or births decrease The carrying capacity is reached.
  11. 11. <ul><li>Density Dependent </li></ul><ul><ul><li>Competition </li></ul></ul><ul><ul><li>Predation </li></ul></ul><ul><ul><li>Parasitism and Disease </li></ul></ul><ul><li>Limiting Factor – a factor that causes the population growth to decrease. </li></ul><ul><li>Limiting Factors can be density dependent or density independent </li></ul><ul><li>Density Independent </li></ul><ul><ul><li>Unusual weather </li></ul></ul><ul><ul><li>Natural disasters </li></ul></ul><ul><ul><li>Seasonal difference </li></ul></ul><ul><ul><li>Human activities </li></ul></ul>