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Community ecology

Community ecology






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    Community ecology Community ecology Presentation Transcript

    • Community Ecology
    • Communities
      • A community is a group of organisms of different species that live in a particular area
    • Individualistic Hypothesis vs. Interactive Hypothesis
      • Individualistic Hypothesis:
        • A community is a chance group of species found in the same area because they have similar abiotic requirements
      • Interactive Hypothesis:
        • A community is a group of closely linked species locked together in mandatory biotic interactions that cause the community to function as an integrated unit
    • Interspecific Interactions
      • Inter specific interactions are interactions that occur between populations of different species living together in a community
      • There are 4 major interspecific interactions:
        • Predation (and parasitism)
        • Competition
        • Commensalism
        • Mutualism
    • Predation (and Parasitism)
      • (+ -)
        • The interaction is beneficial to one species and detrimental to the other
      • Predation:
        • When a predator eats its prey
        • Example in picture:
    • Predation (and Parasitism)
      • Parasitism:
        • Predators that live on or in their hosts, usually feeding off their body tissues or fluids
          • Usually do not kill their hosts
        • Examples:
    • Plant Defenses Against Herbivores
      • “ Plants Fight Back!”
      • Plants have 2 major mechanisms by which they defend themselves against being eaten
        • Mechanical Defenses
          • Thorns, hooks, etc.
    • Plant Defenses Against Herbivores
      • Chemical Defenses
        • Produce chemicals that are distasteful or harmful to an herbivore
        • Morphine (opium poppy)
        • Nicotine (tobacco)
    • Animal Defenses Against Predators
      • Animals defend themselves against predators passively (hiding) or actively (fleeing)
      • Cryptic coloration (camouflage) makes prey difficult to spot
    • Animal Defenses Against Predation
      • Mimicry
        • When one species “imitates” or “mimics” another
        • Batesian mimicry
          • When one edible or harmless species mimics an bad-tasting (unpalatable) or harmful species
          • Example: hawkmoth mimics a snake
    • Animal Defenses Against Predation
      • Mimicry
        • Mullerian mimicry
          • Two species, both of which are unpalatable (taste bad) or harmful, resemble each other
          • Example: monarch butterfly (unpalatable) and queen butterfly (unpalatable) resemble each other
    • Parasitism
      • One organism (the parasite) gets its nourishment from another organism (the host), which is harmed in the process
      • Endoparasites:
        • Live within host tissues (tapeworms)
      • Ectoparasites:
        • Feed on external surfaces (mosquitoes)
    • Interspecific Competition
      • Competition between organisms of different species
      • The Competitive Exclusion Principle:
        • Two species with similar needs for the same limiting resources cannot coexist in the same place
    • Ecological Niches
      • An organism’s niche is the specific role it plays in its environment
        • All of its uses of biotic and abiotic resources in its environment
        • Example: oak tree in a deciduous forest
          • Provides oxygen to plants, animals, etc.
          • Home for squirrels
          • Nesting ground for blue jays
          • Takes water out of the soil
          • Etc., etc.
    • Commensalism
      • (+0) relationship
      • One partner benefits, the other is not affected
      • Examples:
        • Cattle and cattle egret (birds)
        • Sea anemone and clownfish
          • Clownfish gets a place to live, sea anemone is not affected
    • Mutualism
      • (++) relationship
      • Both partners benefit from the relationship
      • “ You scratch my back, I’ll scratch yours”
      • Examples:
        • Mycorrhizae
          • Plant gets increased water/nutrition, fungi gets food
        • Hummingbirds & flowers
          • Hummingbirds get food, flowers can reproduce
    • Dominant & Keystone Species
      • Dominant Species:
        • Species in a community that have the highest abundance or highest biomass
        • Sugar maple in eastern North America
      • Keystone Species:
        • Important to a community because of their ecological roles (niches), not by numbers
        • Sea otters control sea urchin population, which controls kelp population
    • Ecological Succession
      • Ecological succession is a change in the species that live in a given area over a period of time
        • One community replaces another
      • Primary succession = occurs in places where soil is not yet formed
      • Secondary succession = occurs in places where there is soil, but where some disturbance has eliminated the previous community
    • Ecological Succession
    • Ecological Succession
      • The first organisms to inhabit an area undergoing succession are known as pioneer organisms
        • These are usually small organisms (bacteria, lichens, algae, etc.)
      • The ecosystem goes through a number of stages, with each new stage usually consisting of larger organisms than the last one
      • Once a community has become stable and is not changing much, it is known as a climax community
    • Causes of Ecological Succession
      • There are 3 major causes of ecological succession:
        • Human Activities
        • - logging, mining, development, etc.
        • Natural Disasters/Disturbances
        • - fires, volcanic eruptions, etc.
        • 3 . Natural Competition Among Species
        • - Fictitious example:
        • - turtles and frogs both eat crickets
        • - frogs are faster, turtles are slower
        • - frogs eat more crickets, turtles starve
        • - turtle population dies out, frog population
        • gets bigger