Community Interactions

  1. Ecological community
    • Ecological community: all the interacting populations within an ecosystem
  2. biotic
    • biotic, or living, portion of an ecosystem

  3. Interactions between populations in a community help limit their size
    • Populations maintain a balance between resources and the numbers of individuals consuming them
    • The process by which two interacting species act as agents of natural selection on one another is called coevolution

  4. Community Interactions
    • Interspecific (survival & reproduction)
    • Competition, which harms both species (-/-)
    • Predation, which benefits the predator but harms the prey ( +/-)
    • Herbivory (+/-)
    • Symbiosis:
    • Parasitism (+/-)
    • Mutualism (+/+)
    • Commensalism (+/0)
    • Facilitation, not necessarily intimate contact (+/+, 0/+)
  5. Symbiosis
    • Parasitism (+/-)
    • Mutualism (+/+)
    • Commensalism (+/0)

  6. Ecological Niche and Competition
    • Each species occupies a unique ecological niche
    • Its physical home or habitat
    • The physical and chemical environmental factors necessary for its survival
    • nesting sites, climate, and the type of nutrients it needs
    • The role that the species performs within an ecosystem
    • no two species ever occupy exactly the same ecological niche within a community
  7. competitive exclusion principle
    • The competitive exclusion principle states that if two species occupy exactly the same niche with limited resources, one will outcompete the other
  8. resource partitioning
    • resource partitioning: ghost of competition past (coevolution)
    • North American warbler (5 species)
    • all hunt for insects and nest in the same type of eastern spruce tree
    • each species concentrates its search for food in specific regions within spruce trees, employs different hunting tactics, and nests at a slightly different time
    • the warblers minimize the overlap of their niches and reduce interspecific competition

  9. Resource Partitioning
    Different types of warblers eat different parts of the tree
  10. Interspecific Competition- barnacles
    • Interspecific competition may reduce the population size and distribution of each species
    • Chtlamalus and Balanus barnacles
    • Chthamalus occupies the upper shore
    • Balanus occurs in the lower shore
  11. Intraspecific competition
    • Competition within a species is a major factor controlling population size
    • Intraspecific competition: the most intense form of competition
    • major factor controlling population size
    • The evolutionary result is….(you know this!)
  12. herbivores
    • herbivores (animals that eat plants)
  13. predators
    • Predators eat other organisms; these include herbivores (animals that eat plants)
    • carnivores (animals that eat other animals)
    • tend to be less abundant than their prey
    • pursue: fast, agile
    • lie and wait (ambush): disguised

  14. prey
    • Prey behavior: hiding, fleeing, forming schools/herds, alarm calls
    • defensive adaptation: cryptic coloration, warning coloration, mimicry
  15. warning coloration
    • Bright colors often warn of danger
    • Some animals have evolved bright warning coloration that attracts the attention of potential predators
    • Warning coloration advertises that the animal is bad-tasting or poisonous before the predator attacks
    • Examples include poison arrow frogs, coral snakes, and honey bees
  16. Mimicry
    • Mimicry: members of one species have evolved to resemble another species
    • Two or more distasteful species may each benefit from a shared warning coloration pattern (Müllerian mimicry)
    • Predators need only experience one distasteful species to learn to avoid all with that color pattern
    • For example, toxic monarch and viceroy butterflies have similar wing patterns; if a predator becomes ill from eating one species, it will avoid the other
  17. what prey do
    • Camoflague
    • Mimickry- can be aggressive
    • Resembling poisonous species
    • Startle Coloration
    • Chemical Warfare- skunk, squids

  18. Herbivory (+/-)
    • Many plants have evolved chemical
    • adaptations that deter their herbivore
    • predators (toxins, distasteful)
    • milkweed
    • However, monarch butterfly caterpillars have evolved to tolerate the toxins and store them in their tissues as a defense against predation
    • locoweeds: cattle/sheep wander around aimlessly after ingesting, may die as a result
    • distasteful examples include cinnamon, cloves, peppermint

  19. Parasitism (+/-)
    • usually harming or weakening,not immediately killing
    • generally much smaller, more numerous than hosts
    • tapeworms, fleas, ticks, and many types of disease-causing protists, bacteria, and viruses
    • ~1/3 of species on Earth are parasites

  20. Mutualism (+/+)
    • interactions between species in which both benefit (bacteria in digestive tract)

    • Clownfish in
  21. commensalism
    • (+/0)
    • one benefits, one doesnt get effected.
    • barnacles on whale
    • bird on big animal
  22. keystone specie
    • keystone species: plays a major role in determining community structure
    • A keystone species role is out of proportion to its abundance in the community
    • Test its importance by removing it
    • normal community interactions are significantly altered
    • relative abundance of other species changes dramatically
    • Keystone species need to be identified and protected so that human activities do not lead to the collapse of entire communities and ecosystems

  23. Succession: How Do Community Interactions Cause Change Over Time?
    • where the community and its nonliving environment change structurally over time
    • Succession is usually preceded by a disturbance, an event that disrupts the ecosystem either by altering the community, its abiotic (nonliving) structure, or both
    • During succession, most terrestrial communities go through stages

  24. stages of succession
    • Succession begins with arrival of a few hardy plants: pioneers
    • The pioneers alter the ecosystem in ways that favor competing plants, which eventually displace the pioneers
    • Succession often progresses to a relatively stable and diverse climax community (biomes)

    • Recurring disturbances can set back the progress of succession
    • The continuous disturbances maintain communities in earlier, or subclimax, stages of succession

  25. 2 forms of succession
    primary and secondary
  26. primary succession
    • Primary succession occurs from scratch, where there is no trace of a previous community
    • This process may take thousands or even tens of thousands of years
    • The disturbance may be a glacier scouring the landscape to bare rock, or a volcano
  27. secondary succession
    • Secondary succession: occurs after a disturbance changes, but does not obliterate, an existing community, leaving remnants such as soil and seeds

    • Often takes just hundreds of years
  28. example of secondary succession
    • An example is Mount St. Helens, which erupted in 1980 and left a thick layer of nutrient-rich ash that encouraged new growth
    • Another example is fire, which also produces nutrient-rich ash and spares some trees and many healthy roots

  29. Succession culminates in a climax community
    • Succession ends with a relatively stable climax community, which perpetuates itself if not disturbed by outside forces, such as fire
    • The populations within a climax community have ecological niches that allow them to coexist without replacing one another
    • Climax communities have more species and more types of community interactions than do earlier stages of succession
    • Climax species tend to be larger and longer-lived than pioneer species
    • The exact nature of the climax community at a site reflects the local geological and climatic conditions, such as temperature, rainfall, and elevation

  30. A subclimax community example
    • A subclimax community example is the tallgrass prairies that once covered northern Missouri and Illinois
    • Periodic fires maintained the grasses and prevented forests from encroaching

    • lawns. Mowing and use of herbicides keep weeds and woody species in check
    • agriculture. Plowing and pesticides keep competing weeds and shrubs from replacing grains

  31. Climax communities create Earths biomes
    • strongly influenced by climate and geography
    • Extensive areas of characteristic climax plant communities are called biomes
    • deserts, grasslands, and forests
    • These biomes dominate broad geographical regions with similar climates
Card Set
Community Interactions
Community Interactions