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Population Interactions Ch. 51. Ecological Community . Interactions between all living things in an area Coevolution  changes encourages by interactions between two or more species Predator vs. Prey Herbivore vs. Plant Food Availability creates complex interactions:

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ecological community
Ecological Community
  • Interactions between all living things in an area
  • Coevolution changes encourages by interactions between two or more species
    • Predator vs. Prey
    • Herbivore vs. Plant
  • Food Availability creates complex interactions:
    • Optimal Foraging Theory animal must balance the energy spent to get food with the energy they get from eating it; determines diet
    • Specialist eat one or few types
    • Generalist eat almost anything
arms race
Arms Race
  • Prey must adapt methods to protect themselves if they are to survive
    • Hiding places; physical defenses; poisons
    • Aposematic coloration bright, contrasting color patterns that act as a warning of poison
  • Predators must learn to over come these methods too
    • Recognize poisonous prey; hunting skills; immunity to poisons
  • Cryptic coloration camouflage to help hide predators and prey
copy cat
Copy Cat
  • Mimicry resembling the appearance of a another species to gain an advantage
  • Batesian harmless species mimics a dangerous species
    • Mimic gains protection but does not commit energy like the model does
  • Mullerian dangerous species have similarities; predators learn of danger much faster
fight for the right to survive
Fight for the Right to Survive
  • Interspecific competition competing between different species
    • IntRAspecific competition inside a population of one species
  • Interference species directly limit access to resources
    • Lions chase away hyenas
  • Exploitative species lower amount of resources so they are harder to find
    • Birds eat seeds so it is harder for squirrels to find them
  • Competitive Exclusion Principle if two population require the same limited resources in the same way, one will destroy the other
you need a niche
You Need a Niche
  • Niche specific way a species interacts with its environment
    • All successful businesses need a market in order to survive
  • Ecological niche the food type, amount, and space required for a species to survive
    • Fundamental all possible resources that CAN be used
    • Realized all possible resources ACTUALLY used
  • Competition can occur when fundamental niches overlap
cant we all just get along
Cant We All Just Get Along
  • Not all overlapping parts of niches lead to competition
    • All animals breath air but rarely have to compete for it
  • Resource partitioning different species can use the same resources but can get them or use them in different ways
    • Birds species can feed on the same insects but get them different parts of the tree
  • Character Displacement
    • Sympatric species living in the same area are more morphologically different
      • Darwin’s Finches
    • Allopatric species living in different areas are less morphologically different
symbiotic interactions
Symbiotic Interactions
  • Symbiosis physical ecological interactions
  • Commensalism one species benefits and one species is not affected
    • Grass eaters stir up insects that birds will eat
  • Mutualism both species benefit
    • E. coli in your intestine gets nutrients from us and gives us vitamins
  • Parasitism one species benefits (parasite) and one species is negatively affected (host)
    • Tapeworm takes nutrition from our intestine and decreases our health
  • Endoparasites live inside the body
  • Ectoparasites live outside the body
defining a community
Defining A Community
  • Some see communities as “super-organisms”; species in the community are so well connected they require each other to exist and to exist in certain amounts
    • Species composition could reach equilibrium and shifts with major changes
  • Others think communities constantly change and have no strict boundaries or composition
  • Some biomes do have clear boundaries though; Water vs. Land, Aerobic vs. Anaerobic
  • Ecotones edges where communities meet; full of biodiversity
  • ESSAY!!!
  • Explain which of these ideas you most agree with; support with reference material
species diversity
Species Diversity
  • Communities are built around a foundation species (one that stabilize environment)
    • Most often trees/plants
  • One or two dominate species appear (majority of biomass)
  • Species richness # of species present
  • Relative abundance # in each species population
  • Both together make Species Diversity greater the diversity the more stable the environment
movement of energy
Movement of Energy
  • Food Web showing all the predator/prey connections in a community; made of all possible food chains
  • Trophic levels where in the chain a species belongs
    • Primary producers all plant life and photosynthesizers (autotrophs)
    • Primary consumers; herbivores (heterotrophs)
    • Secondary consumers; carnivores/omnivores
  • What is the most important group?
  • Recyclers Detritivores (animals that eat dead material) and Decomposers (bacteria that eat dead material)
complex limits
Complex Limits
  • If species richness and diversity makes communities more stable, why is there not more diversity in nature?
    • Interspecific competition allows only a small number of species to survive
  • What can fight against the selective power of competition?
    • Predator/prey interactions
  • Predators can keep prey in check that are competitors for other species
  • Keystone species a species, that if removed, would have the most dramatic effect on a community’s structure
dealing with disturbances
Dealing with Disturbances
  • A popular theory is that communities will grow to equilibrium points and only shift when disturbances ruin their equilibrium
  • An area experiences flooding after heavy rains throughout the year; r-selected or K-selected dominated?
    • r-selected; community change too often and too quickly for K-species to adapt but r-selected can live their how life cycle between floods
  • An area the experience little disturbances would be K-selected dominated; r-selected kept in check by K-selected predators
  • What amount of disturbance creates the most diversity?
    • Intermediate disturbance hypothesis common but mild disturbances allow mixing of r-selected factors but K-selected can still survive
ecological successions
Ecological Successions
  • Disturbances cause changes (successions) in community composition
  • Primary Succession creating an ecosystem from an area with no soil (after a volcano erupts or new land forms)
  • Lichens live on water and nutrients from rock bed; secret an acid which degrades rock into soil
  • Mosses live and die to build up nutrients
  • r-select plants (grass, ferns) move in and continue process
  • K-selected plants (trees) move in and allow large community to exist
  • Climax community fully plant dominate community; stable until another disturbance comes
other successions
Other Successions
  • Disturbances like fire or storms can cause a Secondary Succession
  • Disturbance removes large percent of plant community but rich soil remains
  • New species fill in spaces in community rapidly
  • Aquatic Succession lakes and rivers fill in to become swamps; then rapid plant growth dries up area becoming a new meadow or forest
are successions predictable
Are Successions Predictable
  • What determines how a community will turn out as Successions occur?
  • Facilitation hypothesis existing species make the area more suitable for other species later on
    • Natural order to growth (lichens make soil for mosses that build soil for plants)
  • Inhibition hypothesis existing species prevent new species from joining by filling their niche
    • No order; randomly based on which species takes niche first
  • Tolerance hypothesis inferior species are replaced by superior ones
    • Competition decides as resources are limited
  • Most likely a combination of all 3 and several other factors
are successions predictable1
Are Successions Predictable
  • Suggested Homework:
    • Test Your Knowledge
  • Actual Homework:
    • Design an Experiment
    • Apply Evolutionary Thinking
    • Due Thursday