17 ch54communityecology2008
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  • Resource partitioning among Dominican Republic lizards. Seven species of Anolis lizards live in close proximity, and all feed on insects and other small arthropods. However, competition for food is reduced because each lizard species has a different perch, thus occupying a distinct niche. Sympatric species often partition available resources, reducing competition between them.
  • clown fish & sea anemone ants & acacia impala & oxpeckers
  • Predation provides a strong selective pressure on prey populations. Ay feature that would decrease the probability of capture should be strongly favored.
  • In the early 1970's, a new corn genotype was released in the US; the "Texas male sterile" (TMS). Hybrids that contained this new characteristic had many desirable properties, and growers were excited about them, planting them over miles and miles of corn acreage in US. They were, of course, bred to be resistant to the most common corn diseases. However, they were not resistant to a previously unimportant strain of a fungal disease; the southern corn leaf blight (caused by the fungus Helminthosporium maydis ). Ninety percent of the corn sowed in the US in 1970 contained the TMS trait and also shared genetic susceptibility to this pathogen. The fungus encountered all this acreage of susceptible host and wiped out one fourth of the US corn crop in 1970, a loss of over one billion dollars in production! If the corn acreage hadn't been such a monoculture, the fungus wouldn't have been able to spread as rapidly, as it would have encountered barriers of genetically resistant plants.
  • Structure of a community may be controlled bottom-up by nutrients or top-down by predators

17 ch54communityecology2008 17 ch54communityecology2008 Presentation Transcript

  • AP Biology Community Ecology population ecosystem community biosphere organism
  • AP Biology Community Ecology  Community  all the organisms that live together in a place  interactions  Community Ecology  study of interactions among all populations in a common environment To answer: In what way do the populations interact? To answer: In what way do the populations interact?
  • AP Biology Fundamental niches Realized niches High tide Low tide Species 1 Species 2 Niche  An organism’s niche is its ecological role  habitat = address vs. niche = job Competitive Exclusion If Species 2 is removed, then Species 1 will occupy whole tidal zone. But at lower depths Species 2 out-competes Species 1, excluding it from its potential (fundamental) niche. Competitive Exclusion If Species 2 is removed, then Species 1 will occupy whole tidal zone. But at lower depths Species 2 out-competes Species 1, excluding it from its potential (fundamental) niche. Chthamalus sp. Semibalanus sp.
  • AP Biology Niche & competition  Competitive Exclusion  No two similar species can occupy the same niche at the same time
  • AP Biology Resource partitioning Reduce competition through microhabitats “the ghost of competition past” “the ghost of competition past”
  • AP Biology Interspecific interactions  Symbiotic interactions  competition (-/-)  compete for limited resource  competitive exclusion!  predation / parasitism (-/+)  mutualism (+/+)  lichens (algae & fungus)  commensalism (+/0)  barnacles attached to whale
  • AP Biology commensalism predation competition Symbiosis mutualism …not very funny for a clown fish +/0 +/+ +/- -/-
  • AP Biology What relationship is this?
  • AP Biology Predation drives evolution  Predators adaptations  locate & subdue prey  Prey adaptations  elude & defend spines, thorns, toxins horns, speed, coloration Predation provides a strong selection pressure on both prey & predator Predation provides a strong selection pressure on both prey & predator
  • AP Biology Anti-predator adaptations  Hide from predators  avoid detection  camouflage  Warn predators  advertise how undesirable you are as prey  aposematic coloration  apo = away & sematic = sign/meaning  Batesian mimicry  Mullerian mimicry
  • AP Biology Defense mechanisms  Camouflage  cryptic coloration whipporwill lizard toadlizard frog
  • AP Biology Mimicry palatable or harmless species mimics a harmful model palatable or harmless species mimics a harmful model Hawkmoth larva puffs up toHawkmoth larva puffs up to look like poisonous snakelook like poisonous snake Hawkmoth larva puffs up toHawkmoth larva puffs up to look like poisonous snakelook like poisonous snake Batesian mimicryBatesian mimicry hawkmoth larvae green parrot snake Convergent evolutionConvergent evolution
  • AP Biology Batesian mimicry Monarch male poisonous Convergent evolutionConvergent evolution fly bee moth bee Which is the fly vs. the bee?Which is the moth vs. the bee? Viceroy male edible
  • AP Biology Mullerian mimicry yellow jacket cuckoo bee two or more protected species look like each other two or more protected species look like each other - group defense?- group defense? - predators may evolve innate avoidance- predators may evolve innate avoidance - group defense?- group defense? - predators may evolve innate avoidance- predators may evolve innate avoidanceMullerian mimicry
  • AP Biology Common warning coloration  Aposematic species come to resemble each other black, red, orange & yellow means: DON’T EAT ME!
  • AP Biology What kind of mimicry? Coral snake is poisonous King snake is not Red on yellow, poison fellow; red on black, safe from attack
  • AP Biology Coevolution in Community  Predator-prey relationships  Parasite-host relationships  Flowers & pollinators Long term evolutionary adjustments between speciesLong term evolutionary adjustments between species
  • AP Biology Characterizing a community  Community structure  species diversity  how many different species  composition  dominant species  most abundant species or highest biomass (total weight)  keystone species  changes over time  succession
  • AP Biology Species diversity greater diversity = greater stability  Greater biodiversity offers:  more food resources  more habitats  more resilience in face of environmental change
  • AP Biology suburban lawnagricultural “monoculture” The impact of reduced biodiversity “old field” compare these communitiescompare these communities  Irish potato famine  1970 US corn crop failure  Irish potato famine  1970 US corn crop failure
  • AP Biology  Influential ecological role  exert important regulating effect on other species in community  keystone species increases diversity in habitat Keystone species Pisaster ochraceous Sea star diversity decreases mussels out-compete other species diversity increases Washington coast
  • AP Biology Keystone species Sea otter is a keystone predator in North Pacific Sea otter is a keystone predator in North Pacific What is theWhat is the impact of theimpact of the Orca whale?Orca whale? What is theWhat is the impact of theimpact of the Orca whale?Orca whale?
  • AP Biology Keystone species Beaver is a keystone species in Northeast & West Beaver is a keystone species in Northeast & West dams transform flowing streams into ponds creating new habitatdams transform flowing streams into ponds creating new habitatdams transform flowing streams into ponds creating new habitatdams transform flowing streams into ponds creating new habitat
  • AP Biology Ecological succession  Sequence of community changes  transition in species composition over time  years or decades  usually after a disturbance Mt. St. Helens
  • AP Biology Primary succession  Begins with virtually lifeless area without soil, then…  bacteria  lichens & mosses  grasses  shrubs  trees make soil {
  • AP Biology Secondary succession  Existing community cleared, but base soil is still intact burning releases nutrients formerly locked up in the tissues of tree burning releases nutrients formerly locked up in the tissues of tree the disturbance starts the process of succession over again the disturbance starts the process of succession over again
  • AP Biology Succession of species lichens & mosses grasses treesbushes & small trees pioneer species climax forest compete well in high sunlight more shade tolerant species shade tolerant species stable community
  • AP Biology What causes succession?  Tolerance  early species are weedy r-selected  tolerant of harsh conditions  Facilitation & Inhibition  early species facilitate habitat changes  change soil pH  change soil fertility  change light levels  allows other species to out-compete
  • AP Biology Climax forest  Plant community dominated by trees  Representing final stage of natural succession for specific location  stable plant community  remains essentially unchanged in species composition as long as site remains undisturbed  birch, beech, maple, hemlock  oak, hickory, pine
  • AP Biology Climax forest  solar energy levels  temperature  rainfall  fertility & depth of soil The species mix of climax forest is dependent on the abiotic factors of the region temperate deciduous forest birch, beech, maple, hemlock taiga
  • AP Biology Disturbances as natural cycle  Disturbances are often necessary for community development & survival - release nutrients - increases biodiversity - release nutrients - increases biodiversity - increases habitats - rejuvenates community - increases habitats - rejuvenates community fire climax forestsfire climax forests
  • AP Biology Fire climax species Jack PineJack Pine adaptations to survive and reproduce in areas than experience frequent fires adaptations to survive and reproduce in areas than experience frequent fires
  • AP Biology When people don’t learn ecology! Building homes in fire climax zones preventing fires makes next year’s fire much worse! preventing fires makes next year’s fire much worse!
  • 2007-2008AP Biology Don’t blow your top! Ask Questions!