Populations

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Populations
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Population Change

• Population Change (birth-death)
  (Immigrants-emigrants)
• The maximum population depends on the biotic
  potential ( the maximum birth rate - the minimum
  death rate and the environmental resistance
  (limits of food space, predation and pollution
  and parasitism.

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Growth Rate

• The growth rate ( r ) birth rate ( b ) - death
  rate ( d )
• Example if birth rate is 1500/10,000 and death
  rate is 500/10,000 then r .1 or 10
• The population growth would them be 10,000
  10(10,000) or 11,000
• The starting population for the next year would
  be 11,000

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Exponential Growth

• The graph of exponential growth is a J shaped
  curve
• The biotic potential depends upon the age of
  reproduction, the frequency of reproduction, the
  average number of offspring, the reproductive
  life span, and the average death rate

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Some Examples

• Bacteria divide every 20 minutes or 3 times an
  hour, if the population were not limited then in
  48 hours a single bacterium would produce a layer
  7 feet deep around the earth.
• The current population of manatees approximately
  2000. Females become reproductive at about age 3
  and produce a single calf every other year for
  10-12 years. Only 1 in three infants survive.
  About 60 manatees die in boating accidents every
  year. What is happening to the population ??

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