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EEB 2244 Final Exam Latest Update
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EEB 2244 Final ExamLatest Update
Community Succession - Answer The change that occurs in the structure and
composition of the community following a disturbance, which may lead back to
pre-disturbance conditions
Disturbances - Answer Events that remove organisms from a community (via mortality)
and open up space for new individuals
When did Connecticut have the least amount of forest cover?
A. 1550
B. 1650
C. 1750
D. 1850
E. 1950 - Answer D
Successional Sequence in New England - Answer - Abandoned fields
- First 2-5 years:
- annual weeds, ragweed, crabgrass
- perennial weeds, Aster, goldenrod
- perennial grasses, e.g. Andropogon
- Next 10 years:
- pitch pine, pasture juniper, gray birch
- Next 25 years:
- scrub oak, white pine, red cedar
- 100-250 years:
- oaks and hickories (on drier, warmer sites)
- maple, beech, hemlock, yellow birch (on cooler, moister sites)
,Sere - Answer Each of the various stage in community succession
Climax Community - Answer - The final, "equilibrium" sere
- in most communities, because of periodic disturbances and recovery, the climax is a
fleeting (transient) sere in the overall dynamics
Primary Succession - Answer - Community establishment and dynamics that occur on
newly formed habitats lacking plants or animals
- sand dunes, lava flow and new volcanoes, landslides, receding glaciers
Secondary Succession - Answer - Changes in community composition and structure
following a disturbance
- fire, wind storms (tornadoes, hurricanes, etc.), floods, agriculture abandonment
Which of these ecologists advocated the view of communities as "superorganisms"?
A. Henry Gleason
B. Charles Elton
C. Henry Cowles
D. Frederick Clements
E) Alfred Lotka - Answer D
Henry Cowles - Answer - Studied succession on sand dunes along Lake Michigan (1899)
- "Space for time substitution"
- could predict how communities would change over time without actually waiting for
the pattern to unfold, which would have taken decades to centuries
F.E. Clements - Answer - Believed plant communities are like "superorganisms," groups
of species working together toward some deterministic end
- thus, succession is similar to the development of an organism
Henry Gleason - Answer - Communities are the random product of fluctuating
environmental conditions acting on individual species
- Communities are not the predictable and repeatable result of coordinated
interactions among species; each community is unique
The Connell-Slatyer Model: Facilitation - Answer - Certain early "pioneer" species
invade the site and subsequently improve the conditions (facilitate) for later species,
which in turn may out-compete pioneers
- nitrogen fixig species (e.g. Alder) or species that build up soil
, - Matches Clements early view of succession
The Connell-Slatyer Model: Inhibition - Answer - Any opportunistic species may colonize
the site and prevent (inhibits) other species from establishing until the earlier species
die out
- In rocky intertidal marine systems, many different species may establish and
dominate a site
The Connell-Slatyer Model: Tolerance - Answer - A variety of different species may
colonize a site. Later on the better competitors come to dominate the site
- forest succession in New England. The earlier tree species tend to be faster growers;
the later species are more shade tolerant
William Cooper - Answer - A student of Cowles, began studies of Glacier Bay in 1915,
seeing it as a "space for time" substitution opportunity
- Observed increasing plant species richness and change in composition with time and
distance from the melting ice front
- pioneer stage is dominated by lichens, mosses, horsetails, willows, and cottonwoods
- 30 years: Dryas community develops, followed by the Alder stage
- 100 years: mature Sitka spruce forest is in place
- 200 years later, species richness decreases somewhat as Sitka spruce are replaced
by Western hemlocks
Regional Biogeography - Answer Regional differences in species diversity are
influenced by area and distance, which determine the balance between immigration and
extinction rates
Island - Answer Any kind of isolated area surrounded by dissimilar habitat
Regional Biogeography: Islands - Answer - Large islands have more species than small
islands
- Islands species diversity also shows a strong negative relationship to distance from a
source of species
MacArthur and Wilson (1963) - Answer - Plotted bird species richness and island area
for a group of islands off New Guinea
- Islands of equal size had more species if they were closer to New Guinea
- Developed the Equilibrium Theory of Island Biogeography:
- The number of species on an island depends on a balance between immigration rates
and extinction rates
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