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Community Ecology
Biology of Population and Communities
69
Biology
Undergraduate 1
09/21/2013

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Term
community
Definition
assemblage of plant and animal population that live in a particular area/habitat
Term
interaction
Definition
populations of various species in a community utilize, decompose, compete with, and alter the fate of each other
Term
community ecology
Definition
seeks to explain the underlying mechanisms that create, maintain, and determine the fate of biological communities
Term
patters
Definition
documented observations/used to generate hypotheses
-vegetatoin zonation
-species lists
-seasonal distribution of activity
-association of certain species
Term
processes
Definition
-herbivore
-competition
-predation risk
-nutrient availability
-patterns of disturbance
-energy flow
-history
-evolution
Term
emergent properties of a community
Definition
-spatial and temporal structure
-species richness
-species diversity
-trophic structure
-succession and disturbance
Term
spacial structure
Definition
way species are distributed relative to each other
ex. trees in a tropical rainforest
Term
temporal structure
Definition
-timing of the appearance and activity of species
-some communities have very pronounced temporal seasons
Term
species richness
Definition
number of species in a community
Term
diversity
Definition
number of species in the community related to their relative abundance
Term
Diversity equation
Definition
D= 1- Sum(Pi)^2
1- [(a/total)^2 + (b/total)^2 + (c/total)^2 + ect..]
Term
species richness "equation"
Definition
number of species listed
Term
ecological succession
Definition
-predictable changes in species over time, as each new set of species modifies the environment to enable the establishment of other species
-ubiquitous (universal)
Term
disturbances
Definition
events that damage communities, remover organisms from them, and alter resource availability
Term
invasion
Definition
-disturbances create an ecological vacuum that can be filled from within, the outside, or both
-best invaders have good dispersal powers and many offspring (not good competitors)
Term
succession
Definition
-recovery of life
-driven by the interactions among dispersal, ecological tolerances, and competitive ability
-primary/secondary
Term
Agents of Disturbances
Definition
-fire
-flood
-drought
-large herbivores
-stroms
-volcano
-human activity
Term
invasion
Definition
Term
primary succession
Definition
on newly exposed land-forms that have not previously been influenced by a community (ie. after glaciers)
Term
secondary succession
Definition
when vegetation of an area has been partially or completely removed, but where soil/seeds/spores remain
Term
climax community
Definition
-more or less permanent and final stage of a particular succession, often characteristic of a restricted area
-slow rates of change
-dominated by species tolerant of competition of resources
Term
F.E. Clements
Definition
-argued that communities work like an integrated machine
-have predictable compositions
-somewhat of an oversimplification
Term
Henry Gleason
Definition
hypothesized that random events determined the composition of communities
-was right
Term
are biological communities real functional units? (clements)
Definition
-communities are stable, functional units with a fixed composition-each integrated part needs the others
-every area should ultimately have the same species, given time
Term
are biological communities real functional units? (gleason)
Definition
-composition is unstable and variable
-communities like assemblages of everything that can live together in one place
Term
trophic interaction
Definition
-transfer of energy
-hierarchy of feeding in a community
i.e. eating, decomposing, obtaining energy via photosynthesis.
Term
food web
Definition
follows the transfer of energy from bottom to the top
Term
food chain vs. food web
Definition
-food chain is ONE PATH through a food web
-food web has many different paths
Term
ecological niche
Definition
-organism’s habitat, the resources it uses, and its way of making a living, within the context of a community
-reflected by it's place in food web (what it eats/what it competes with, what eats it)
Term
**each organism has the potential to create niches for others
Definition
Term
keystone species
Definition
-disproportionately important in communities
-if removed, entire ecosystem collapses
Term
examples of keystone species
Definition
-California Sea Otters: This species preys upon sea urchins, allowing kelp forests to become established.
-Pisaster Starfish: Grazing by Pisaster prevents the establishment of dense mussel beds, allowing other species to colonize rocks on the Pacific Coast.
-“Mangrove” Trees: Mangrove seeds disperse in salt water. They take root and form a dense forest in saltwater shallows, allowing other species to thrive
-The Acorn Banksia: At certain times of year, Banksia prionotes is the sole source of food for honeyeaters, which in turn, are the pollinators for many other species of plants in Western Australia.
Term
trophic cascade
Definition
-species at one trophic level influence species at other levels
-the positive and negative outcomes of changing a trophic level
(ie. removing a secondary consumer might positively affect the primary consumer they feed upon and negatively affect the producter that are food for primary consumers
Term
Top Down effect
Definition
-upper level consumers directly affect the lower end
-diomass of hervivores was positively correlated to the biomass of producers, when introduced fish that eat herbivores, the producers increased
Term
Bottom Up effect
Definition
-lower level producer directly affect the population size of the upper level consumers
Term
competition
Definition
occurs when organisms in the same community seek the same limiting resource
Term
intraspecific competition
Definition
competition among members of the same species
Term
interspecific competition
Definition
competition among members of different species
Term
exploitation competition
Definition
occurs when individuals use the same limiting resources, thus depleting the amount of available to others
Term
interference competition
Definition
occurs when individuals interfere with the foraging, survival, or reproduction of others, or directly prevent their physical establishment in a portion of a habitat
(ex. beetles cannibalize eggs of own/other species)
Term
exclusion
Definition
-outcome of exploitation competition
-one organism mus require less of the limiting resource to survive
-dominant species must reduce the quantity of the resources below some critical level
Term
coexistance
Definition
partitioning the resources
Term
competitive exclusion principle
Definition
two species cannot compete for the same limiting resource for long
Term
resource partitioning
Definition
-Species that share the same habitat and have similar needs frequently use resources in somewhat different ways - so that they do not come into direct competition for at least part of the limiting resource
(ex. dif species living in different parts of trees)
Term
character displacement (?)
Definition
-sympatic populations of similar species frequently have differences in body structure relative to allopatric population of the same species
-similar species with same characteristics will differ when living in the same area together (ie. finch beaks)
Term
fundamental niche
Definition
set of resources and habitats an organism could theoretically use under ideal conditions
Term
realized niche
Definition
set of resources and habitats an organism actually used: it is generally much more restricted due to interspecific competition (or predation.)
Term
Gausse's Rule
Definition
-two organisms cannot occupy exactly the same niche
Term
amensalism
Definition
(-0)

one species suffers and the other interacting species experiences no effect
Term
allelopathy
Definition
(-0)
-production and release of chemical substances by one species that inhibit the growth of another
-can be seen as amensalism
Term
secondary substances
Definition
chemicals produced by plants that seem to have no direct use in metabolism
Term
commensalism
Definition
interspecific interaction where one species benefits and the other is unaffected.
(frequently live in the nests, or on the bodies, of the other species)
Term
mutualism
Definition
interspecific interaction between two species that benefits both members.
-population of each species grows at higher rate in the presence of the other species
Term
mutualistic symbiosis
Definition
type of mutualism in which individuals interact physically, or even live within the body of the other mutualist.
(relationship is often essential for the survival of at least one member) (ex. lichens)
Term
facultative Mutualisms
Definition
are not essential for the survival of either species but helpful
Term
obligate mutualisms
Definition
essential for the survival of one or both species
Term
Predators, parasites, parasitoids, and herbivores
Definition
obtain food at the expense of their host/prey
Term
predators
Definition
tend to be larger than prey and consume many prey during their lifetime
Term
parasites/pathogens
Definition
-smaller than host
-consume host from inside/outside
-pathogens are parasitic microbes-many generations live in same host
parasites may have one->many hosts
Term
endoparasites
Definition
consume host from inside
Term
ectoparasites
Definition
consume host from the outside
Term
parasitoids
Definition
hunt their prey like predators but lay eggs within the body of a host where they develop
Term
herbivores
Definition
animals that eat plants
Term
J.B.S Haldane
Definition
suggested that the interaction between parasite and hose should resemble and evolutionary arms race
Term
evolutionary arms race
Definition
-First a parasite (or predator) evolves a trait that allows it to attack its host (or prey).
-Next, natural selection favors host individuals that are able to defend themselves against the new trait.
-As the frequency of resistant host individuals increases, there is natural selection for parasites with novel traits to subvert the host defenses.
-This process continues as long as both species survive.
Term
Predator-Prey Population Dynamics
Definition
-The degree of prey mortality is a function of the density of the predator population
-The density of the prey population, in turn, affects the birth and death rates of the predator population
-lag effect
-needs to be a balance
Term
coarse grained
Definition
-when predators drive their prey to extinction
-no alternate prey -> they die
-makes habitat available for recolonization by the prey species in another area
Term
three outcomes of predation
Definition
-prey extinct -> predator extinct
-prey extinct -> find new prey
-time-lag effect -> predator-prey oscillations
Term
Lotka-Volterra Curve
Definition

-assumes that prey destruction is a function not only of natural enemy numbers, but also of prey density -predicts the predator-prey oscillations sometimes seen in nature

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