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Ecology

Ecology. Population Dynamics. Why do we want to measure population sizes?. To better manage populations To better use resources increase population size endangered species (So they don’t go extinct) decrease population size pests maintain population size fisheries management

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Ecology

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  1. Ecology Population Dynamics

  2. Why do we want to measure population sizes? • To better manage populations • To better use resources • increase population size • endangered species (So they don’t go extinct) • decrease population size • pests • maintain population size • fisheries management • maintain & maximize sustained yield

  3. How do we measure plant and animal populations? • Tagging (mark-recapture) • Netting • Electroshocking • Radio collars • Traps • Animal counts (ex: deer yards) • Counting plants • estimate over large areas

  4. Fyke netting in spring

  5. Tagging

  6. Electroshocking

  7. Electroshocking

  8. Electroshocking • Stream electroshocking

  9. Radio tracking

  10. Netting animals

  11. Traps

  12. What changes a Population’s Size? • Changes to population size • adding & removing individuals from a population • birth • death • immigration • emigration

  13. Natural populations of organisms • Natural populations do NOT show linear growth!

  14. Natural populations demonstrate exponential growth

  15. Exponential growth rate • Characteristic of populations without limiting factors • introduced to a new environment or rebounding from a catastrophe Whooping crane coming back from near extinction African elephant protected from hunting

  16. Limits to population growth • Limiting factors – • any environmental factor that limits an organism’s ability to survive in its environment • Examples???? • Predators

  17. Regulation of population size marking territory= competition • Limiting factors • density dependent • Biotic factors • competition: food, mates, nesting sites • predators, parasites, pathogens • density independent • abiotic factors • sunlight (energy) • temperature • rainfall swarming locusts competition for nesting sites

  18. Carrying capacity • The number of organisms of one species that an environment can support over an extended period of time.

  19. 10 8 Number of breeding male fur seals (thousands) 6 4 2 0 1915 1925 1935 1945 Time (years) 500 400 Number of cladocerans (per 200 ml) 300 200 100 0 0 10 20 30 40 50 60 Time (days) Carrying capacity • Maximum population size that environment can support with no degradation of habitat • varies with changes in resources What’s going on with the plankton?

  20. Changes in Carrying Capacity • Population cycles • predator – prey interactions At what population level is thecarrying capacity? K K

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