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Community Ecology

Community Ecology. Interactions between populations. Density dependent factors. Operate as negative feedback mechanisms The population maintains a steady level Disease transmission Vulnerability to predators Food supply Over crowding. What Controls Population Size and Growth Rate.

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Community Ecology

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  1. Community Ecology Interactions between populations

  2. Density dependent factors • Operate as negative feedback mechanisms • The population maintains a steady level • Disease transmission • Vulnerability to predators • Food supply • Over crowding

  3. What Controls Population Size and Growth Rate • Density-dependent factors: • Intra-specific competition • Food • Space • Contagious disease • Waste production • Inter specific competition • Other species interactions • Density-independent factors: • disturbance, environmental conditions • Hurricanes • Floods • Colder than normal winter

  4. Types of Interactions • Competition • Predator-Prey • Mutualism • Commensalism • Parasitism

  5. Competition Natural Selection minimizes competition!

  6. Competition: • If two species are competing, the growth of one population should reduce the size of the other

  7. Predator-prey

  8. Predator-Prey Relationships • Prey defenses: avoid conflict! • Coevolution • as predator evolves, prey evolves to evade it • Warning coloration and mimicry • Camouflage

  9. Predator-Prey Relationships • Predators can promote diversity by • keeping competition in check

  10. Idealized Predator-Prey Population Graph

  11. Predatory-Prey If it is a predator-prey relationship, then the two populations have opposite effects on one another

  12. Mutualism • Both species benefit

  13. Mutualism • If it is a mutually beneficial relationship, then the two populations increase each other’s size

  14. Commensalism • One species benefits, the other is unaffected

  15. Is this mutualism or commensalism?

  16. Commensalism • If the relationship is commensalistic, one species benefits (the commensal) and the other is unaffected

  17. Parasitism

  18. Test you knowledge! What type of relationship–? • A coati eats tree fruit. • Your dog has a flea • You use a fast bicyclist to “draft” off of

  19. Carrying Capacity The number of individuals that a habitat can support. If the population is a herbivore, K may depend on the population of plants

  20. Community Dynamics Community: a group of populations (both plants and animals) that live together in a defined region.

  21. Trophic Levels Eagles 4th trophic level predator/ tertiary consumer predator/ secondary consumer Foxes 3rd trophic level herbivore/ primary consumer 2nd trophic level Mice autotroph/ primary producer Plants 1st trophic level

  22. Trophic Levels Eagles 4th trophic level if eagles go extinct, what could happen to… foxes? mice? plants? Foxes 3rd trophic level 2nd trophic level Mice Plants 1st trophic level

  23. Trophic Levels Eagles 4th trophic level If a new predator on mice is introduced, what could happen to… mice? plants? foxes? eagles? Foxes 3rd trophic level 2nd trophic level Mice Plants 1st trophic level

  24. Trophic Levels Eagles 4th trophic level If drought caused a dip in plant production, what would happen to… mice? foxes? eagles? Foxes 3rd trophic level 2nd trophic level Mice Plants 1st trophic level

  25. Simplified Temperate Forest Food WebWhat happens to when it’s a WEB instead of a CHAIN? Eagle Wolf Fox Shrews Deer Caterpillars Rabbit Oak seedling Grasses Herbs In long term, balance is restored

  26. That is the end!

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