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Community Ecology (Predator-Prey Interactions (one predator, one prey…

- - - - predators feeding rate
        
        how quickly a predator can find a new prey
        
        faster rate if more prey is available
      - handling time
        
        time needed to consume the prey
      - two combined represent the predators' functional response
        
        dependent on prey density= prey dependent
    - - =net rate of change in prey numbers
      - dN/dt=rN-aNP
        
        dN/dt is rate of change with time of the prey population
        
        r is the intrinsic rate of increase for prey
        
        N is the number of prey species in the community
        
        a is the predator's per capita attack rate
        
        units= number of prey eaten per prey per predator
        
        prey dependent
        
        P is the number of individuals present
      - net rate of change of predator numbers is dP/dt=faNP-qP
        
        dP/dt is rate of change over time for predators
        
        f is a constant representing predators' efficiency at converting prey eaten into new predators
        
        q is the predators' per capita mortality rate
      - population of prey will be stable, neither increasing or decreasing
        
        dN/dt=0
        
        rN-aNP=0
        
        rN=aNP
        
        r=aP
        
        r/a=P
        
        population of prey is stable when density of the predator equals r/a
        
        predators population stable when dP/dt=0
    - - =paradox enrichment
    - - fixed effort harvesting is the population health determined by the amount that can be harvested with effort
        
        fixed quota harvesting is individuals being allowed to harvest a particular amount
  - - - 3 factors determine a predators choice of prey
        
        probability that a particular prey individual will be encountered
        
        decision for predator to attack the prey once encountered
        
        probability that an attacked prey item is successfully eaten
        
        optimal foraging theory examine interactions between these factors
        
        produced an optimal diet model with four predictions
        
        predators should prefer the prey with highest energy yield
        
        predator broadening its diet to include lower energy yielding prey
        
        some prey items will always be consumed, and others will never be eaten
        
        probability of being eaten depends partially on the abundance of other plants that are easy to handle and have a higher energy yield
        
        animals are a more valuable prey so omnivores will tend to go for the animal prey ignoring plants completely
    - - several species often compete for the same resources
        
        light
        
        water
        
        minerals
        
        exploitation competition is when organisms consume the same resource and make it less available
        
        interference competition is when one organism restricts another organisms resource access even though the first may not be using it
      - two competing species can coexist if each species has a greater negative effect on its own per capita growth rate then the per capita growth rate of the competitor
        
        may also coexist if one or the other can increase from low density even in the presence of the other
        
        this species may become invasive
    - - a increase in one plant species associated with a decrease in another
        
        appear to be in competition, but are not competing against one another
- - - - relationships are not free
      - flowers either produce nectar or losing pollen that is eating
      - plants must supply carbs to fungi or bacteria
      - cheating develops as organisms try to obtain benefits without paying costs
  - - - =spiny desert shrubs
    - - organisms become established on newly created substrates
        
        substrates= volcanic ash and glaciers freeing soil of all organisms
        
        pioneer species move in
        
        able to handle harsh conditions
        
        mutualistic relationships between nitrogen-fixing bacteria
- - - - very difficult to map
      - difficult to trust due to being incomplete
      - keystone species used to see affect on the structure of the community in its absence or presence
- - - - usually incomplete
      - not all organisms are cataloged
    - - diversity of growth forms
      - feeding methods of herbivores
      - diversity of primary producers, secondary, and decomposers
  - - - larger = more diverse
        
        larger population, so less likely to die out if a disturbance occurs
      - smaller = less diverse
      - relation between species and are richness is species-area relationship
        
        alpha diversity = number of species or growth forms at a local, or small site
        
        beta diversity= compares difference between several smaller sites within a larger region
        
        gamma diversity= number of species within a area
      - no community will have equal numbers of individuals of every species
        
        species abundance distribution used
  - - - many proposed theories on why this occurs
        
        regions near the equator have more benign environments, where as higher latitudes have more severe conditions
        
        fewer organisms capable of adapting to these conditions
        
        geographical and geological play a role as well
        
        high latitudes= no ice-free land
        
        recently discovered evidence of Earth's climate history indicates that temperate conditions are recent
        
        earth used to have a much warmer, tropical climate
        
        certain areas went from tropical to temperate
        
        organisms have had millions of years to adapt to tropical conditions, but not as long to adapt to temperate
- - - - environment composed of many discrete patches in which a species can live
      - some patches are occupied by the species whereas others are not
      - empty patches become populated via migration
      - populations within individual patches can go extinct in that patch
    - - low quality habitats= sink habitats