community structure Flashcards
define keystone species
species that has a disproportionate impact on the community relative to its abundance
what happens if you remove a keystone species?
it initiates changes in community structure and often results in loss of diversity
what happens as you move across a landscape?
biological and physical structure of the community changes AND as you travel farther, the more pronounce changes become
what happens as you move across a landscape?
biological and physical structure of the community changes AND as you travel farther, the more pronounced changes become
define zonation
changes in physical and biological structure of communities as one moves across the landscape
define community
group of species that occupy to a given area and interact either directly or indirectly
what is species richness
number of species in the community
what is species diversity
species richness and species evenness
ecological succession is?
process by which an ecosystem matures and develops. it is gradual, sequential and predictable change
define succession
gradual change in plant and animals communities in an area following disturbance
primary succession on ___ exposed geological substrates
newly
secondary succession following ____ that ____ destroy soil
disturbances, do not
define climax community
late-successional community that remains stable until disrupted by disturbance
define primary succession
development of a new ecosystem in an area previously devoid of organisms
define secondary succession
regrowth of an ecosystem after a disturbance and it is more rapid than primary because soil building is not required
example of primary?
bare rock to climax forest
stage 1: lichen pioneer community
stage 2: moss community
stage 3: herbaceous community
stage 4: shrub community
stage 5: tree community
stage 5: climax forest or equilibrium community - association of organisms best adapted to the physical conditions of a defined area
example of secondary succession?
old field succession
1y: dominant; crabgrass
2y: dominant; asters
3rd-18thy: grass shrub community
19th-30thy: young pine forest
30th-70th: mature pine forest
70th-100thy: pine to hardwood transition
100thy+ climax oak-hickory forest
define intermediate disturbance hypothesis
highest diversity will occur at levels of moderate disturbance
(t/f) as succession occurs, overlap will occur
true
what other community changes as plant community changes
animal
zonation vs succession
succession is temporal change and zonation is spatial change
define early successional species
plant species with high dispersal rates, ability to colonize disturbed sites, short life span, shade-intolerant “pioneer species”
define late successional species
long-lived, shade tolerant, plant species that supplant early successional species, low rates of dispersal colonization
primary vs secondary succession
primary occurs on a site previously unoccupied by a community and secondary occurs on previously occupied sites after a disturbance
define chronosequence
group of sites within same area that are in different stages of succession
what happens under high frequency of disturbance?
absence of later successional species reduces overall diversity
what happens at intermediate frequency of disturbance?
all species coexist and diversity is at maximum
what happens when disturbance is absent?
later successional species eventually displace earlier ones and diversity is now low
what is a food web?
looks at movement of matter and energy throughout a community
define keystone predation
predation that is central to the organization of a community
environmental changes can be?
allogenic or autogenic
define autogenic
direct result of the activities of organisms in the community (biotic)
define allogenic
successional change brought about by a change in the physical environment (abiotic)
species colonization ___ species richness
increases
species replacement ___ number of species present
decreases
