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59 Cards in this Set
- Front
- Back
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biological community
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an assemblage of populations of various species living close enough for potential interaction
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interspecific interactions
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relationships b/w species in a community
e.g. competition, predation, herbivory, & symbiosis |
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interspecific competition
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(-/- interaction) occurs when species compete for a resource in short supply
e.g. grasshoppers & bison compete for grass |
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competitive exclusion
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local elimination of a competing species
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competitive exclusion principle
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* states that 2 species competing for the same limiting resources cannont coexist in the same place
*one species will always use the resources more efficiently, gaining reproductive advantage that will eventually lead to local elimination of the inferior competitor |
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ecological niche
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*the total sum of a specie's use of abiotic and biotic resources in its environment
*organisms ecological "role" *e.g. temp. toleratation/time of day when active/resources it consumes |
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identical niches
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competitive exclusion principle; species cannont coexist permanently in a community
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niches differ
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species CAN coexist if niches differ in one or more ways
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resource partitioning
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*differentiation of ecological niches
*enabling similar species to coexist in a community |
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fundamental niche
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niche potentially occupied occupied by a species (but can't due to competition)
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realized niche
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the niche a species actually occupies in a particular environment
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predation
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(+/-) interaction where one species, the predator, kills & eats the other, prey
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cryctic coloration
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camouflage, makes prey difficult to spot
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aposematic coloration
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chemical defense that often exhibit bright warning coloration
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batesian mimicry
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a palatable (harmless) species mimics an unpalatable (harmful) model
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mullerian mimicry
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2 or more unplatable species resemble each other
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herbivory
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(+/-) interaction in which an herbivore eats parts of a plant/algae
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plants chemical weapons
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*strychnine, nicotine, & tannins
*cinnamon, cloves, & peppermint *chemicals that cause abnormal development in insect herbivores |
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symbiosis
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*includes all direct & intimate relationships b/w species, wheather harmful, helpful, or nuetral
*parasitism *mutualism *commensalism |
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parasitism
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(+/-) one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process
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endoparasites
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parasites that live w/in the body of their host
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ectoparasites
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parasites that live on the external surface of host
*e.g. parasitoid insects (wasps) |
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mutualism
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(+/+) interspecific interaction that benefits both species
e.g.acacia tree & aunts |
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obligate
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mutualism: one species cannot survive w/o the other
e.g. lichen=fungus+algae |
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facultative
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mutualism: both species can survive alone
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commensalism
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(+/0) interaction where one species benefits & the other is apparently unaffected
e.g. cattle egret & bison |
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Fundamental features of community structure (2)
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*species diversity
*feeding relationships |
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species diversity
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*variety of oranisms that make up the community
*2 components: species richness & relative abundance |
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species richness
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*component of species diversity
*total # of different species in the community |
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relative abundance
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*component of species diversity
*proportion each species represents of the total individuals in the community *2 species can have same species richness, but a different relative abundance |
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trophic structure
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*the feeding relationshps b/w organisms in a community
*key factor in community dynamics |
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food chain
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transfer of food energy up the trophic levels from is source in plants & other autotrophs (primary producers) through herbivores (primary consumers) to carnivores (secondary & tetiary consumers) & eventually decomposers
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food web
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*uses arrows to link species according to who eats whom in a community
*a given species may weave into the web @ more than 1 trophic level e.g. fox |
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energetic hypothesis
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*food web length is limited by ineffecient energy transfer
*10% of energy actually gets transerred through each trophic level |
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biomass
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the sum weight of all individuals in a population
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dynamic stability hypothesis
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*long food chains are less stable than short ones
*population fluctuations @ lower trophic levels are magnified @ higher trophic levels, making top predators vunerable *shorter food chains in unpredictable environments |
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dominant species
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*those that are most abundant or have the highest biomass(total mass of all individuals in a population)
*exert powerful control over occurrence & distribution of other species *e.g. sugar maple trees |
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invasive species
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*can achieve high biomass in their new environments, thus becoming dominant species
*absense of their natural predators & agents of disease (so they grow exponentially) *e.g. zebra mussels |
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keystone species
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are not necessairly abundant in a community, but they influence community structure by thier key ecological niches
*e.g. sea stars & pisaster |
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foundation species
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*cause physical changes in the environment that affect community structure e.g. beaver dams
*act as FACILITATORS (+ impact) |
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facilitators
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* species that have positive effects on the survival & reproduction of other species (foundation species)
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bottom-up model
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*community organization; proposes a unidirectional influence from lower to higher trophic levels
*e.g. mineral nutrients stimulate growth of vegetation, then biomass of higher trophic levels should also increase |
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top-down model
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*aka trophic cascade model, proposes that control comes from the tropic level above
*e.g. removing top carnivores will increase the abundance of primary carnivores, in turn decreasing the number of herbivores, increasing phytoplankton abundance, and decreasing concentrations of mineral nutrients |
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biomanipulation
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attempts to prevent algae blooms & eutrophication by altering the density of higher level consumers in lakes insead of using chemical treatments
*e.g. removing fish will increase zooplankton thus decreasing algal populations |
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nonequilibrium model
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communities constantly change after being affected by disturbances
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disturbance
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event that changes a community by removing orgnaisms or altering resource availability e.g. storms, floods, overgrazing, & fires
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intermediate disturbance hypothesis
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suggests that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance
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ecological succession
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sequence of community & ecosystem changes after a disturbance
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primary succession
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begins in lifeless area where SOIL HAS NOT YET FORMED.
*starts w/ autotrophic prokaryotes & heterotrophic bacteria |
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secondary succession
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an existing community has been removed by a disturbance, but the SOIL IS LEFT INTACT.
*herbaceous (plants) species grow 1st |
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SUCCESION: early arrivals & later arriving species are linked (3 key proesses)
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1. facilitate (herbaceous species may increase soil fertility)
2. inhibit; prevents species from establishing 3.tolerate (niether hinder nor help) |
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2 key factors correlated w/ community's biodiveristy (species diversity)
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1. geographic location
2. size |
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evapotranspiration
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*evaporation of water from soil plus transpiration of water from plants
*much higher in hot areas w/ abundant rain fall |
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potential evapotranspiration
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measure of potential water loss that assumes water is readily available, is determined by the amount of solar radiation & temperature
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species richness is related to ....
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a community's geographic size
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species-area curve
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the larger the geographic area of a community, the greater the # of species
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2 factors determine the # of species that eventually inhabit an island
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1. rate which new species immigrate to island
2. rate which species become extinct on island |
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2 physical factors of island that affect immigration & extinction
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1. size
2. distance from mainland |
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equilibrium model of island biogeography
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maintains that species richness on an ecological island levels off at dynamic equilbrium point
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