11/1 quiz Flashcards
what are the two outcomes of competition?
coexistence or one species dominates
what is coexistence?
resources or niches are partitioned
realized niche is expanded for one species as one moves away
what is single species domination?
competitive exclusion principle
other species goes extinct, migrates, or evolves
what type of evolution results from single species domination for losing species?
change in niche or character displacement
what is ecological character displacement?
evolution of differences in traits among similar species to reduce competition while in the same area
difference between species is greater when species are in sympatry than when in allopatry
limited resources lead to…
competition between and within species
competition occurs when:
a) a resource is limiting
b) the interaction between species has a negative impact on one or both of them
how do we know who wins in competition?
the best competitor for the resource
meaning whoever can persist at the lower level of the resource (competitive exclusion principle)
what is an example of environment influencing competition?
flour beetles in warm/dry vs cold/wet flour
what type of competition caused the wildebeest population to level off?
intraspecific
example of logistic growth and density-dependent factors
what is equilibrium in population growth?
when the population is neither growing, nor decreasing
what factors determine the size of a population at equilibrium?
growth rate and carrying capacity for that environment (intraspecific competition)
how can we model intraspecific competition?
dN/dt = rN(1-(N/K))
change in population size = change in population size if resources are limited times limited resources
what happens in mathematical model of intraspecific competition if N = K?
change in population growth = 0 and population stops growing as it has hit equilibrium
what is our model for interspecific competition?
lotka-volterra model
why does the l-v model work?
the species affect each other because they use the same resource
what is the l-v model for species 1?
dN/dT = rN(1- (N+aN**)/(K))
change in population size for species 1 (N*) = unlimited resource times (intraspecific competition and interspecific competition)
what is alpha?
competition coefficient for the effect of species two on species one
effect of gazelles on wildebeest
if one gazelle consumes the equivalent of half a wildebeest, what is a?
0.5
what is the l-v model for the effect of species one on species two?
dN/dt = rN** ( 1- N** + bN*)/K**)
what is b?
competition coefficient for effect of species one on species two
what are zero-growth isoclines?
when the population is at equilibrium
what happens for the species on the x-axis if x = 0?
their competitor’s population has gone extinct and the main species is at its carrying capacity
it is only experiencing intraspecific competition
n
o
which direction does the x-axis species’ arrows move?
horizontally
n
o
what happens to the y-axis species when y = 0?
the species has gone extinct and its competitor’s population = K**/b
what are the possible outcomes of l-v models?
species 1 or 2 dominates
unstable equilibrium
stable equilibrium
what does the graph look like during stable coexistence?
isoclines cross and carrying capacities are the lowest intercepts
two species co-exist
net movement arrows all point to intersecting point of isoclines
which way do y-axis species population arrows move?
vertically
environmental variation can allow competitors to…
coexist
what happens in l-v model when one species dominates?
isoclines don’t cross
outer isocline wins and the other goes extinct
outer net movement arrows point towards isoclines but the one btwn lines points towards winning species’ axis
what happens in l-v model for unstable coexistence/competitive exclusion?
isoclines cross
carrying capacities are the highest intercepts
outer arrows lead to unstable coexistence
segment arrows point to their closest axis for competitive exclusion of other species
why is unstable coexistence unstable?
any perturbation (changes in reproduction from generation to generation, natural disasters, etc.) leads to one segment dominating
what are predator-prey interactions?
interactions that result in a predator killing something
all species except primary producers are both ___ and ___ for consumers
consumers and resources
what do predators do?
catch and consume individuals, remove them from the population