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Ch 26 community ecology (Community (has boundaries in both time and place,…

- - - - e.g. a forest
    - - communities come and go
  - - - e.g. re-introducing wolves into yellowstone
- - - - checklists
        
        a count of species within a community
        
        always incomplete
        
        impossible to list all organisms within a community
      - Diversity and scale
        
        scale
        
        larger areas are more diverse than smaller ones
        
        species-area relationship
        
        describes the relationship between area snd species richness
        
        expressed by S=cA"z
        
        S= number of species
        
        A= area
        
        c,z= constants that must be discovered by studying individual communities
        
        generally described in several distinct sizes
        
        Alpha diversity
        
        number of species or growth forms that occur at a local, small site
        
        beta diversity
        
        compares differences between several small sites within a larger region
        
        e.g. small sites within a a large forests
        
        Gamma diversity
        
        number of species within a region
        
        species abundance distribution
        
        describes the total abundance of a species instead of treating them all equally
        
        does not describe most communities accurately
      - diversity and latitude
        
        far northern areas have much fewer species
        
        higher latitudes have more severe climates
        
        also due to ice coverage
        
        also due to habitable land coverage
        
        e.g lots of mountains in alaska
        
        as the earth evolved into its current state, zones became cooler
        
        the whole earth used to be tropical in climate
        
        indicates that temperature conditions are recent
        
        areas near the equator are a more temperate climate
- - - - dN/dt=rN-aNP
        
        dN/dt
        
        rate of change with time of the prey population
        
        when equal to 0, this line on a graph illustrates predator population that will keep the prey population stable
        
        r
        
        intrinsic rate of increase for the prey species
        
        N
        
        number of individuals of prey species in the community
        
        a
        
        predators per capita attack rate
        
        p
        
        number of predator individuals present
        
        net rate of change in prey numbers
      - dP/dt=faNP-qp
        
        dP/dt
        
        rate of change with time of the predator population
        
        =0 means the population will be stable
        
        f
        
        a constant indicating the predators efficiency at converting the prey it has eaten into new predators
        
        q
        
        the predators mortality rate(independent of population density
      - often criticized for being too simplistic
    - - adds more factors
      - zero growth isoclines are curves rather than straight lines
    - - a prey species becomes so overabundant that a predator overexploits the resource
    - - harvesting just enough of something to maintain its population density
      - not enough is known to determine the correct amount
    - - only harvesting for a maximum amount of time or effort to maintain population size
      - e.g. hunting seasons
    - - only allowing a certain number of something to be harvested
  - - - how quickly a predator finds new prey
      - will be faster with more prey available
    - - time needed for the predator to consume the prey
    - - dependent on prey density
  - - - probability that a certain prey will be encountered
        
        abundant species more readily consumed
        
        decision by the predator to attack an individual
        
        probability that an attacked prey will be successfully eaten
        
        studied by optimal foraging theory
        
        produced an optimal diet model
        
        makes 4 predictions
        
        predators should prefer whichever prey yields the most energy
        
        predators would be more successful when broadening its diet to include less energetic, but easily accessible prey
        
        some prey will always be eaten, some will never be eaten
        
        the probability of a plant being eaten depends on the availability of higher value plants the are also easy to eat
  - - - organisms consume a shared resource
      - makes the resource less available for other organisms
    - - one organism restricts another organism's access to a resource
        
        the first organism may not even use the resource
    - - can increase from very ow population numbers even with a competitor present
    - - any substance or factor that cn lead to increased growth rates as its availability is increased
  - - - it appears they are in competition, but plants obviously are not
- - - - e.g. pollinators and the plants they pollinate
  - - - e.g. beavers creating ponds
        
        plants and animals surviving in the pond benefit, but the beaver doesn't benefit from them
    - - alter a small area of habitat below them that benefits other plants
        
        plants that benefit could eventually kill the nurse plant
    - - as new areas are created, the initial plants that colonize help create more livable soil
- - - - high quality patch
    - - low quality patch
    - - fugitive species
    - - assisted dispersal
        
        the planned moving of organisms between patches
  - - - a region of the environment is composed of many discrete patches in which the species can live
      - some patches are occupied by the species, other suitable patches are not
      - empty patches will become colonized by migration from occupied patches
      - populations within individual patches have a probability of going extinct within that patch
- - - - e.g. plants
      - produce their own energy
    - - eat primary producers for energy
    - - eat primary consumers for energy