Ecology Unit 2

R-selected

“fast organisms;” organisms that grow quickly, reproduce early, produce many offspring, and invest relatively little in each offspring

K-selected

“slow organisms;” organisms that mature later, produce fewer offspring, invest more heavily in them, and tend to live longer

life history

resource allocation across a lifetime

frequency/intensity, resource availability

the two axes of Grime’s CSR model are ___ and ___

Grime’s CSR model

two-axis framework that asks what environmental problem an organism is adapted to solve

competitor, stress-tolerator, ruderal

the three strategies described by the CSR model

competitor

“capture and crowd” strategy

stress-tolerator

“save and survive” strategy

ruderal

“race to reproduce” strategy

productivity

the rate of biomass production

low productivity

at ____, only stress-tolerant species persist

high productivity

at ____, strong competitors or ruderals under high disturbance can dominate and exclude others

intermediate productivity

at ____, a variety of strategies can coexist

36

in the park grass experiment, the starting richness at zero added resources was about __ species

3

in the park grass experiment, each additional resource corresponded to a decline of about __ species

0.49, 49

in the park grass experiment, R² = __; about __% of variation in richness was explained by number of added resources

high-productivity

in the park grass experiment, the plots began as fertile agricultural land, so this represents the ____ side of the broader relationship

habitat complexity, species diversity

habitat structural diversity demonstrates a positive relationship between ___ and ___

foliar height, bird

MacArthur’s work linked greater ____ diversity to greater ___ diversity because more vertical structure creates more nesting, foraging, cover, and prey-use opportunities

disturbance

removes biomass or damages individuals through processes such as fire, floods, storms, grazing, or herbivory

intermediate disturbance hypothesis

predicts that species richness is greatest at intermediate disturbance

low disturbance

strong competitors dominating and competitively excluding other species is the expected community outcome of a ____ level (competitors win)

intermediate disturbance

neither competitive dominants nor disturbance specialists completely dominating is the expected community outcome of a ____ level, where coexistence is highest

high disturbance

only rapid colonizers / ruderals persisting reliably is the expected community outcome of a ____ level (ruderals win)

direct effect

species A acts directly on species B

indirect effect

species A affects species C through one or more intermediates

density-mediated indirect effect

species A changes the abundance of intermediate species B, which changes C

trait-mediated indirect effect

species A changes B’s behavior or traits, which changes C without necessarily changing B’s abundance

keystone species

species that has a disproportionately large effect on community structure relative to its abundance

Paine’s sea star experiment

in ____, removing sea stars allowed competitive dominants to expand, causing species richness to collapse

keystone predator

dominant competitors can be suppressed by the presence of a ____

bottom-up control

effects propagate upward through trophic levels (food pushes upward)

top-down control

alternating effects cascade downward through trophic levels (predators push downward in a cascade)

population

consists of all individuals of one species occurring together in space and time

habitat availability, biotic interactions, dispersal

population distribution is shaped by ____, ____, and ____

geographic range

spatial extent over which a species occurs

cosmopolitan species

broadly distributed over a large geographic range

endemic species

restricted to a particular region or specific habitat conditions

abundance

total number of individuals in a population (how many)

density

number of individuals per unit area or volume (how many per space)

dispersion

observed spatial pattern of individuals within the population

clumped dispersion

individuals aggregated in patches; often caused by social behavior, vegetative reproduction, or patchy resources

random dispersion

no predictable spacing; requires relatively homogeneous habitat plus random establishment

even dispersion

individuals maintain similar spacing; often associated with territoriality, competition, or home ranges

dispersal

movement to a new location where the individual remains

migration

repeated or seasonal movement with return

cohort

a ____ life table follows a group of individuals born at the same time from birth to death of the last individual

static

a ____  life table quantifies the survival and fecundity of all individuals in a population during a single time interval

B

which population, A or B, is poised to continue experiencing positive population

growth?

I

which curve, labeled I, II, or III, reflects likely survivorship patterns for large mammals?

II

which curve, labeled I, II, or III, reflects likely survivorship patterns for small mammals and birds?

III

which curve, labeled I, II, or III, reflects likely survivorship patterns for turtles, fish, and plants?

geometric

N_t = N₀λ^t, the equation for the ____ growth model, is used for population growth that occurs in distinct, non-overlapping steps or generations

geometric

doubling time=ln(2)/ln(λ) for the ____ model

exponential

N_t = N₀e^rt, the equation for the ____ growth model, is used for population growth that occurs continuously in real time, with overlapping generations

dN/dt=rN

differential form (rate of change) for exponential growth

exponential

doubling time=ln(2)/r for the ____ model

fecundity

number of offspring an individual will produce during reproductive episodes

parity

number of reproductive episodes an organism experiences

trophic cascade

indirect effects initiated by a predator

ruderals

have the fastest growth rate

competitors

have a fast growth rate

stress-tolerators

have a slow growth rate

stress-tolerators

allocate the most energy to defense

competitors

allocate less energy to defense

ruderals

allocate the least energy to defense

ruderals

sexually reproduce the most

competitors

sexually reproduce less

stress-tolerators

sexually reproduce the least

environmental stress, resource scarcity

at low levels of resource availability, species richness is limited by ____ and ____

resource availability, ecological interactions

at moderate levels of resource availability, species richness reaches its maximum because of a balance between ____ and ____

competitive exclusion

at high levels of resource availability, species richness declines sharply due to ____

low

____ levels of disturbance allow competitive exclusion to take over

high

____ levels of disturbance cause high mortality, which resets community development continuously

competitive exclusion

strong, fast-growing, or competitively dominant species monopolize essential resources, driving weaker species to extirpation

negative density-dependent growth

per capita growth rate of a population decreases as the population size or density increases

resource competition

one cause of negative density-dependent growth

positive density dependence

the circled segment of the curve indicates ____

negative density dependence

the bracketed segment of the curve indicates ____

mate availability

one factor that leads to positive density dependence

all the same

in a Basic Metapopulation Model, the level of variation in habitat suitability among patches is ____

all the same

in a Basic Metapopulation Model, the level of variation in subpopulation sizes is ____

all the same

in a Basic Metapopulation Model, the potential for individuals to migrate to any particular subpopulation is ____

varies

in a Landscape Metapopulation Model, habitat suitability among patches ____

vary

in a Landscape Metapopulation Model, subpopulation sizes ____

distance from other patches, matrix quality

in a Landscape Metapopulation Model, the potential for individuals to migrate to any particular subpopulation depends on factors like ____ and ____

sink populations

inhabit poor quality habitats which cannot support a large enough growth rate for the population to persist

source populations

inhabit high quality habitats

source, sink, sink

immigration rates from ___ to ___ are higher than emigration rates, which offsets population decline and allows the ___ population to persist

source, sink

individuals from ___ populations must emigrate to ___ populations when the amount of per capita benefit in their habitat gets lower

death, birth

in sink populations, ___ rates exceed ___ rates

birth, death

in source populations, ___ rates exceed ___ rates

larger, less isolated

occupied patches tend to be ___ and ___

small, small

___ populations in ___ patches are highly vulnerable to dying out from random occurrences like extreme weather, disease, or fluctuating birth rates

large, large

___ populations in ___ patches can easily absorb random shocks, leading to a much lower rate of extirpation

resources, habitat diversity

large patches provide more ___ and ___

immigration

patches that are less isolated experience significantly higher rates of ____, which prevents the patches from becoming empty

genetic diversity, finding mates

in smaller, isolated patches, there is less ____ and increased difficulty ____

exponential growth

the blue line depicts ____

logistic growth

the red line depicts ____