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Population Ecology

Population Ecology. Chapter 53. Populations . Population - a group of individuals of the same species living in the same area Population Ecology – explores how biotic and abiotic factors influence the density, distribution, size and age structure of populations Density

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Population Ecology

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  1. Population Ecology Chapter 53

  2. Populations • Population - a group of individuals of the same species living in the same area • Population Ecology – explores how biotic and abiotic factors influence the density, distribution, size and age structure of populations • Density • Dispersion (distribution) • Demography (size/age structure)

  3. Population Ecology • Density – the number of individuals per unit area; increases by births or immigration, decreases by death or emigration • ***Dispersion – pattern of spacing among individuals*** (STUDENT PRESENTATION #1) • Demography – study of vital statistics of a population, especially birth and death • Life tables – age specific • ***Survivorship Curves: *** (STUDENT PRESENTATION #2) • Reproductive Tables – fertility schedule and # of offspring produced

  4. Life History is… • Made up of traits that affect an organism’s schedule of reproduction and survival • Influenced by 3 variables: 1) age when reproduction begins 2) how often the organisms reproduces 3) the number of offspring during each reproductive event (surviving offspring) Consider “r” and “K” selected species

  5. r vs. K Selected species “r ” strategists • Many young • Little/no parental care/low energy investment in young • Small size of young • Reach sexual maturity quickly • Semelparous reproduction (only happens once) • Short life span • Type III survivorship curve • Not prone to extinction “K” strategists • Few young • Lots of parental care/high energy investment in young • Large size of young • Slow to reach sexual maturity • Iteroparous reproduction (many reproductive events) • Long life span • Type I survivorship curve • Prone to extinction

  6. Models of population growth ***Exponential Population growth models*** (STUDENT PRESENTATION #3) • r-selected species ***Logistic Population growth models*** (STUDENT PRESENTATION #4) • K-selected species

  7. Many factors regulate population growth Density-dependent factors: birth and death rates that fall and rise as population density rises (ex. – competition for resources, territoriality, disease, predation, toxic waste) AND Density-independent factors: death rate does not change with population density increases (ex. – natural disasters – will wipe out population regardless of its density) (STUDENT PRESENTATION #5)

  8. Population dynamics • The study of complex interactions between biotic and abiotic factors that cause variation in population size • Ex – predator-prey relationships/interactions • Ex – large mammals are impacted by cold, wet winters weakens sheep and decreases access to food; large populations of sheep are influenced by parasites in warm weather = dec. pop. size • Immigration/Emigration/ Metapopulations • Metapopulations: local populations are linked

  9. Human population growth • Human population growth is increasing rapidly, but no longer exponential – read pg. 1190-1191 aloud Global pop.Global pop. 8000BC – 2000AD 1950 - 2050

  10. Human population growth • Human global carrying capacity is unknown (1,000,000,000 to 1,000,000,000,000 but average estimate is 10-15,000,000,000) • ~6.86 billion today (up from 6.6 billion at time of book’s publication) + 75,000,000/yr or 200,000 people/day • Ecological footprint concept can be used to summarize the amount of land and water area required by each person for resources consumed and wastes produced • 1.7 hectares/person needed • 10 hectares – amount of land the average American uses

  11. Age structure pyramids (STUDENT PRESENTATION #6)

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