1 / 23

Are we over carrying capacity?

Are we over carrying capacity?. Population density/consumption patterns. Quality of life issues. Impact on landscapes & resources Lake Chad. What is “overpopulation”?. how does it occur?. Outline. Basic Dynamics of Population Growth Exponential vs. Arithmetic Growth

yaholo
Download Presentation

Are we over carrying capacity?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Are we over carrying capacity?

  2. Population density/consumption patterns

  3. Quality of life issues

  4. Impact on landscapes & resourcesLake Chad

  5. What is “overpopulation”? how does it occur?

  6. Outline • Basic Dynamics of Population Growth • Exponential vs. Arithmetic Growth • Malthusian vs. Logistic Growth • Complex Patterns of Population Change • Regulating Population Growth • Density Dependence vs. Independence • How do we apply possibilities to a specific case?

  7. DYNAMICS OF POPULATION GROWTH • Exponential Growth - Growth at a constant rate of increase per unit time (Geometric) • Arithmetic Growth - Growth at a constant amount per unit time (independent of base)

  8. Exponential Growth and Doubling Times • Number of individuals added to a population at the beginning of exponential growth is relatively small. • But numbers increase quickly as the reproductive base of the population grows. • J curve is the result of exponential growth • Doubling Time of a population: • 70/annual percentage growth rate.

  9. Irruptive Growth • Malthusian Growth (Irruptive) - Population explosions followed by population crashes. • Malthus concluded human populations tend to grow exponentially until they exhaust their resources and then crash. • Non-human examples are common, but may be influenced by predators or parasites, not just resources

  10. Irruptive population examples

  11. Short life Rapid growth Early maturity Many small offspring Little parental care Little investment in individual offspring. Adapted to unstable environment. Pioneers, colonizers Niche generalists Prey Regulated mainly by extrinsic factors. Low trophic level Malthusian Strategies

  12. Biotic Potential and Carrying Capacity • Biotic Potential - Maximum reproductive rate of an organism (births minus deaths in optimal conditions). • Carrying Capacity - Maximum number of individuals of any species that can be indefinitely supported

  13. Growth to a Stable Population • Logistic Growth - Growth rates regulated by internal and external factors until coming into equilibrium with environmental resources. • Growth rate slows as population approaches carrying capacity. • S curve • Environmental Resistance - Any environmental factor that reduces population growth.

  14. Long life Slower growth Late maturity Fewer large offspring High parental care and protection. High investment in individual offspring. Adapted to stable environment. Later stages of succession. Niche specialists Predators Regulated mainly by intrinsic factors. High trophic level Logistic Strategies

  15. Population Oscillations around Carrying Capacity • Overshoot - Measure of extent to which population exceeds carrying capacity of its environment. • Dieback - Negative growth curve. • Severity of dieback generally related to the extent of overshoot.

  16. FACTORS THAT ADD TO POPULATIONS • Natality - Production of new individuals . • Fecundity - Physical ability to reproduce. • Fertility - Measure of actual number of offspring produced. • Immigration - Organisms introduced into new ecosystems.

  17. LOSSES: Mortality and Emigration • Mortality - Death Rate. • Survivorship - Percentage of cohort surviving to a certain age. • Life expectancy - Probable number of years of survival for an individual of a given age. • Increases as humans age. • Life Span - Longest period of life reached by a given type of organism. • Emigration - Movement of individuals out of a population.

  18. FACTORS THAT REGULATE ADDITIONS AND LOSSES • Intrinsic factors - Operate within or between individual organisms in the same species. • Extrinsic factors - Imposed from outside the population. • Biotic factors - Caused by living organisms. • Abiotic factors - Caused by non-living environmental components.

  19. Density-Independent Regulatory Factors • Constant proportion of the population is affected regardless of population density. • Tend to be abiotic components affecting mortality. • The risk (per individual) is unrelated to the density of individuals (e.g, tsunami).

  20. Density-Dependent Factors • Intensity changes as the population density changes. • Tend to reduce population size by decreasing natality or increasing mortality. • Interspecific Interactions • Predator-Prey oscillations • Intraspecific Interactions • Territoriality • Stress and Crowding • Stress-related diseases

  21. Given a long list of possible factors promoting growth, for a specific case, what leads to overpopulation or extinction? • Identify most likely influences • (create a simplified “model”) • Test the predictions of the model • Example, what are the most likely influences on population levels of White-tailed Deer in Knox County?

More Related