Ch. 54 pt. 2 Flashcards
Dominant species
most abundant or have the highest biomass
Invasive species
may become dominant because they lack natural predators or parasites
Keystone species
exert strong control on a community by their ecological roles, or niches
not abundant
remove one species, whole thing falls apart
Ecosystem engineers (foundation species)
cause physical changes in the environment that affect community structure
ex. beaver dams
Bottom up model
unidirectional influence from lower to higher trophic levels
presence of mineral nutrients, controls plant numbers, control herbivore numbers, controls predator models
Top down model (trophic cascade model)
control come from the trophic level above
predators limit herbivores, herbivores limit plants, and plants limit nutrient levels
Mesopredator release
populations of medium sized predators rapidly increase in ecosystems after the removal of larger, top carnivore
Biomanipulation
deliberate alteration of an ecosystem by adding or removing species, especially predators
F.E. Clements argument
plant communities had only one state of equilibrium, a climax community, controlled by climate
A.G. Tansley argument
variation in abiotic conditions created many possible stable communities within a region
H.A. Gleason
viewed communities as chance assemblages of species with similar abiotic requirements
Disturbance
an event that changes a community, removes organisms from it, and alters resource availability
Nonequilibrium model
communities as constantly changing after disturbance
High level of disturbance
result of frequent and intense disturbance
exclude slow growing species
Low levels of disturbance
result from low frequency or low intensity of disturbance
dominant species exclude less competitive species
Intermediate disturbance hypothesis
moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance
Ecological succession
the sequence of changes in community composition following a disturbance
Primary succession
occurs where no soil exists when succession begins
Early arriving species three processes
facilitate the appearance of the later species
inhibit the establishment of later species
no affect on the establishment of later species
Pioneering plants
liverworts, mosses, fireweed, Dryas, and willows
facilitate later arrivals by increasing soil nitrogen content
Succession is the result of?
changes induced by the vegetation itself
Secondary succession
where soil remains after a disturbance
abandoned agricultural land may return to its original state
Two biogeographic factors that affect the species diversity of biological communities
latitude and area
Species richness
is especially great in the tropics and generally declines in a gradient toward the poles
