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
what do parasites do?
consume part of a host but don’t remove them from the population
what do parasitoids do?
reside within host and then kill it
what do herbivores do?
predatory or parasitic depending on whether they eat the entire plant or just part of it
how do generalist-diet predators select food?
based on its availability
specialized-diet predators…
focus on a specific species
a general rule of thumb for predators is that the bigger the size of the prey, …
the more specialized the predator’s adaptations become
what is an example of a specialized predator’s adaptations?
lions having powerful legs and jaws
how can predators develop adaptations for handling prey?
arrangement of teeth
think predator vs. herbivore teeth
what is cooperative hunting?
hunting in groups
unique scenario where predators is smaller than prey
what allows smaller predator to successfully attack larger prey?
overpowering prey with numbers and having enough bodies to make the hunt useful (can feasibly eat entirety of prey)
what is a digestive example of predator adaptations?
plant predators have longer foregut regions to process organic matter
cellulose and lignin are difficult to digest and longer foregut allows for more surface area and bacteria to interact with food
what are the types of prey adaptations to predation?
behavioral and morphological
what are the different types of behavioral adaptations for prey?
hiding: baby deer
escaping: adult deer
group living: zebras
sentinels/lookouts: meerkat
playing dead: possum
what are morphological prey adaptations to predation?
size: elephants are too big to eat by one predator
spines/armor-like covering: porcupines or turtles
unpalatability: foul-smelling or stinging secretions - skunks
aposematic coloration: monarch butterflies and caterpillars
what is aposematic coloration?
bright colors or patterns to seem foul-tasting or toxic to predators
what aren’t all potential prey unpalatable?
energetic costs
danger of obtaining toxin from environment without harming self and needing to have a specialized diet
not all toxins work on all species (think birds vs. humans and hot peppers)
what happens to poison dart frogs after they stop eating the food they get their toxin from?
they are no longer toxic to touch
what is batesian mimicry?
palatable animals mimic unpalatable species
what is mullerian mimicry?
unpalatable species mimic each other
a predator’s bad experience with one species protects all species in the “mullerian complex”
what does disruptive coloration do?
confuse the visual system of predator
cause predator to attack tail or other non-vital parts of the body
what is crypsis?
coloration that blends into the environment
used by both prey and predator
what is countershading?
top and bottom sides of organism are different shadings to made it harder for them to be seen from above or below
what are the three types of impacts predators have on prey?
no, moderate, and dominant impact
what is no impact?
“donor-controlled supply”
prey supply is determined by factors other than predation
what is moderate impact?
population cycles bc populations aren’t static
predator mandated coexistence
what is dominant impact?
predator controlled system
predator depletes prey
what happens if predator is removed from a no impact system?
nothing
prey N and r are determined by non-predator factors (abiotic, resources, disease, etc.)
what are predator prey interactions the result of?
interactions between predator and resource limitations on prey
can predator interactions be positive?
yes, if the predator eats the prey and then disperses it, it can be positive for the species but not the individual
or squirrels forgetting seeds underground
when do dominant impact interactions typically occur?
when a predator is introduced to a system
what is predator-mandated co-existence?
when predation keeps prey populations regulated to prevent competitive exclusion of other species
promotes existence of other prey species
efficient predators can cause…
their own extinction
what are trends in predation dynamics?
long-cycle herbivores tend to have l-c predators
short cycle herbivores tend to have s-c predators
large herbivores have 9-10 yr cycles
small herbivores have 4 yr cycles
why does the response of prey populations (or vice versa) lag?
responding to environment and offspring, which takes time
what is the rule of thumb for lag periods?
a predator will experience a lag 4-5 times behind the prey population
needs time for resource to effect prey, then for predator to react, be effected, and then effect the prey again
if there’s one year between birth and sexual maturity, how long is the lag cycle?
four years
at equilibrium, the change in predator and prey populations is ___
zero
the equilibrium isocline of a predator is…
the number of prey that can sustain growth of the predator population
the equilibrium isocline of the prey is…
the number of predators that the prey population can support
what is population trajectory?
a closed cycle that occurs if p-p populations are graphed together
1/4 cycle out of phase, prey inc/decreases ahead of predator
what is joint equilibrium in the l-v model?
when lines representing P and V cross, only combination of populations sizes of P and V that is stable
l-v model predicts that once populations stray from joint equilibrium point,…
they will continue to oscillate around it
oscillation period is inversely proportional to…
the better predators are at using resources and the faster prey grow
the higher the growth rate of the prey or death rate of the predator, the faster the system oscillates
both l-v models for prey and predators are set up as…
birth rate - death rate
what does c mean in l-v p-p interaction models?
predator efficiency
how good predators are at catching things
what does the a mean in l-v p-p interaction models?
prey’s efficiency at turning food into reproduction
what does m mean in l-v p-p interaction models?
death rate
what does the vertical line on l-v p-p interactions graph show?
number of prey where predators population is at equilibrium
what does the horizontal line show in l-v p-p interaction models?
number of predators where prey population is at equilibrium
what does population trajectory show?
how we get an offset in cycling
species are responding to each other simultaneously
roughly a quarter of a cycle out of phase
why were the paramecium initially not coexisting with the didinium?
they were getting eaten too quickly
then they were too good at hiding in glass wool
what are environmental requirements for predator prey coexistence?
limited resources for prey to limit population growth
spatial variation in environment
why don’t all predator prey interaction result in oscillations?
predator insufficiency
independent factors that lead to density-dependent limitation of predator or prey
alternative food sources for predator
refuges for prey at low densities
what is meant by predator inefficiency?
that prey may escape or be defensive
in the end, more prey survive and their populations increase, leading to support of predator populations and enhancement of stability
what happens when predators have alternative food sources?
populations aren’t reduced drastically
what happens when refuges for prey are at low densities
prey numbers are not reduced drastically and their can recover more easily
hiding is a density dependent factor
