Populations

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.

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

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

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 ??