community interactions and disturbances

what are communities

collection of species that are grouped together by their dominant organisms or the physical condition that’s affect the distribution of species

what two factors does community diversity take into account

species richness and species evenness

what is species richness

the number of species In a community

what is species evenness

the relative proportion of individuals in a community represented by each species

what can be used to visualize both species richness and relative abundance within a community 

log-normal distribution and a rank-abundance curve

the log-normal distribution groups abundances into

discrete categories on the x-axis

what is a keystone species

a species whose presence or absence can affect species diversity

what can a keystone species be

a predator, parasite, herbivore or competitor

in intertidal communities what are the keystone species

sea stars

what is the intermediate disturbance hypothesis 

more species are present in communities that experience occasional disturbances than in communities that ex[erience frequent or rare disturbances 

what does this graph represent

intermediate disturbance hypothesis

what kind of species are typically in low disturbance areas 

k-selected species 

what kind of species are typically in high disturbance areas

r-selected species

t/f: the intermediate disturbance hypothesis lacks empirical evidence and has substantial theoretical flaws

true

what are the flaws of the intermediate disturbance hypothesis

• doesn’t represent a real mechanisms, but rather a pattern

• lack of causation

• too flexible; cant’ make predictions

• outdated

what are food webs 

complex and realistic representations of predator/prey relationships 

what are trophic levels

primary producers or primary consumers

how are organisms grouped into trophic levels

based on how they acquire every

what are food chains

strictly linear representations of nutrient and energy flows through a community

what is the downside to food chains versus food webs 

food chains are too simple to be useful 

how can species affect each other

through direct or indirect effects which are depicted through effect maps

what is bottom-up control

when the number of trophic levels in a community is limited by the amount of energy available from producers

what is top-down control

when the number of trophic levels is limited by predation

are bottom-up and top-down control mutually exclusive

no, it can be both