ecology exam 2

species interactions definition

relationships between species

species interactions affect

evolutionary change and distribution/abundance of species

3 possible outcomes for any organism in an interaction

positive, negative, neutral

symbiosis

most or all life cycle for 1 organism occurs inside or on another

symbiosis ranges from

+/+ to -/-

mutualism

both species benefit

commensalism

one species benefits and the other is unimpacted

predation and parasitism

one organism benefits while other is negatively affected

parasitism definition

lives on/in host without killing it

amensalism

one species is harmed and other is unaffected

allelopathy

a kind of amensalism where one organism releases chemicals that harm the other

species compete for

food, water, light, space

INTERspecific

between species

INTRAspecific

within a species

interference competition

competitor directly interferes with access to limiting resource (physically or chemically)

exploitative competition

resource competition indirectly though depletion of shared, limited resources

species interactions are

a continuum; not always clearcut

community is defined as

all interacting organism inhabiting a specific area

communities exclude

abiotic factors

ecologists study communities by focusing on

species number, abundance, and identity; or more narrowly: taxonomic affinity, guild, life form

most species are _______ abundant

moderately

lognormal distribution

distribution of species in communities is approximately bell shaped

usually, only part of a lognormal curve is visible because

rare species are difficult to detect and therefore study

more sampling leads to

a more complete curve

species richness

number of species

species evenness

relative abundance of species

communities can have the same _____ but different _____

richness; evenness

rank abundance curves

plotting relative abundance vs rank in abundance

lower slope in rank abundance curve indicates

greater evenness

species diversity is greater when

environmental structure is more complex or heterogenous

example of species diversity increasing with more complex environment

bird complexity increases as foliage height diversiy increases

primary producer communities often live in

simple environments and compete for same limiting resources yet are very diverse

diatoms differ in competitive exclusion and coexistence depending on

availability of limiting nutrients in lab aquaria

complexity in aquatic plant envrionments

nutrients vary naturally creating heterogeneity

complexity in terrestrial plant environments

soil nutrients, pH, and moisture vary widely, providing niche diversity that supports plant diversity

______ and _____ create complexity in plant environments

soil and topographic heterogeneity

example of topographic heterogeneity

variation in soil type and groundwater depth creating 6 different tropical rainforest plant communities within a short distance

nutrient enrichment can

reduce environmental complexity and lead to lowered species diversity

example of nutrient enrichment lowering diversity

adding fertilizer to plots allows strong competitor species to dominate weak species

ecological disturbances definition

events that kill or injure organisms creating opportunities for new individuals in communities

ecological disturbances tend to be

abiotic like fire, flood, hurricane, drought

______ is more common in regard to disturbance and stability

changing conditions rather than equilibrium

intermediate disturbance hypothesis j connell

predicts that intermediate levels of disturbance promote greatest species diversity

at high/frequent disturbances

few species can survive or colonize

at low/infrequent disturbances

competitive exclude weaker species