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Lecture

Population Ecology Continued.docx

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Department
Biology
Course
BIOL 103
Professor
Peter T Boag
Semester
Winter

Description
Population Ecology Continued - Populations can temporarily exceed carrying capacity - Logistic Population Growth = stability - Rare example of exponential population growth when four males and 22 female reindeer introduced to Alaskan island, grew to over 2000 in 30 years, overgrazed habitat and population crashed to 8 animals by 1950 - At the peek, the population exceeded carrying capacity of the island - Near the end of the graph, there was no food because the environment was overgrazed - i-Clicker Question: Some organisms have peculiar population cycles, such as the various species of Periodic Cicadas, with species that emerge only every 7, 13, 17, or 19 years from below ground. This might be since these are all prime numbers, it reduces the likelihood a predator population can track them with an overlapping cycle of it’s own - Two or more species with interacting populations can give complex patterns; some populations are stable while other fluctuate and crash o Food supply and predators may cause a steep decline - Life history traits are those closely linked to Darwinian fitness (e.g. clutch size, age at 1 reproduction, longevity, etc.) and evolve in response to biotic and abiotic factors o Semelparous reproduction  Common in insects, fish, some plants which use all their energy in a single, immense reproductive effort, e.g. salmon dying after spawning or annual weeds  Reproduce one time in their lifetime  Have a short lived life o Iteroparaous reproduction  Exhibit repeated reproductive cycles throughout their lifetimes, often invest more in each offspring, e.g. many large trees, mammals, birds o More general comparison of ‘r-selected’ versus ‘K-selected’ species o r-selected usually are semelparous too  they maximize r o k-selected tend to be larger, longer lived, population size is rather stable, density dependent stable long term pattern o Natural selection c
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