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Unit 3 Notes

Unit 3 Notes. Biotic Potential vs. Environmental Resistance. Biotic Potential. Reproductive capacity ( r) - a measure of biotic potential; rate that members of a population reproduce if unlimited

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Unit 3 Notes

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  1. Unit 3 Notes Biotic Potential vs. Environmental Resistance

  2. Biotic Potential • Reproductive capacity (r)- a measure of biotic potential; rate that members of a population reproduce if unlimited • For an organism to survive past the early life stages and become part of the reproducing population is called recruitment • Each organism will have a different amount • Humans may only have one offspring per year, while fish may lay 100s of eggs in a year

  3. Environmental Resistance • We very rarely see unlimited population growth due to bioticand abioticfactors influencing environmental resistance • Biotic Factors are predators, parasites, competitors, and lack of food • AbioticFactorsinclude unusual temperatures, moisture, light, fire, just to name a few

  4. Comparison

  5. Reproductive Strategies • Produce massive numbers of offspring, leaving survival to kill off most of the young • Results in low recruitment (what is recruitment again?) • High reproductive rate • High mortality rate • Small organisms • Sometimes called r-strategists • r-strategists: organisms that have a high “r” value (or “reproductive” value)

  6. Reproductive Strategies • Produce low numbers of offspring, but provide care and protection to allow the organism to survive to adulthood • Organisms are well-adapted to their environment • Low reproductive rate • Low mortality rate • Often called K-strategists • K-strategists: populations that fluctuate around the carrying capacity (also called “equilibrial” species)

  7. r-strategists vs. K-strategists

  8. Survivorship Curves • Life History:characteristics such as age at first reproduction and the length of life that determine survivorship curves • Survivorship Curves demonstrate the number remaining from a group of organisms all born at the same time, shown decreasing over time until the maximum life span for the species is met

  9. Survivorship Curves • Type I • Low mortality rate throughout life, and most live to old age • Type II • Intermediate mortality and life expectancy • Type III • Produce many offspring, with early mortality rate

  10. Survivorship Curves

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