Card Set Information
BIOL 1215-19 Community Ecology
Species diversity and feeding relationships.
Variety of organisms that make up the community.
Two communities can have
same species richness
different relative abundance
Compared using a
Total number of different species in community.
Proportion each species represents of total individuals in community.
Shannon Diversity Index (H):
H = -[(p
) + (p
) + (p
) + ...]
Determining number and abundance of species is difficult.
Molecular tools used to determine microbial diversity.
Species with a Large Impact:
Highly abundant or pivotal in community dynamics.
Powerful control over occurence and distribution of others.
Most competitive for resources or fewest predators.
Total mass of individuals in population.
Introduced to new environment by humans, often lack predators or disease.
Strong control on community by
Not necessarily abundant in a community.
Cause physical changes in environment affecting community structure.
Some facilitate +'ve effects on survival and reproduction of others.
Bottom-Up and Top-Down Controls:
is unidirectional influence from
low to high
Presence or absence of mineral nutrients determines community structure.
trophic cascade model
) is coming
Predators control herbivores, which control primary producers.
Event changing community, removing organisms, altering resource supplies.
Climax community functioning as a superorganism debunked.
No longer believed to be in equilibirium.
Fire is significant disturbance in terrestrial ecosystems. (often necessary)
Community is constantly changing after buffeted by disturbances.
Intermediate Disturbance Hypothesis:
Moderate disturbance fosters greater diversity than high or low disturbance.
High disturbance exclude slow-growing species.
Low disturbance allow dominant species to exclude less competitive species.
Sequence of community and ecosystem chang after a disturbance.
Occurs where no soil exists when succession begins.
Area where soil remains after a disturbance.
Greatest impact on biological communities worldwide.
Usually reduces species diversity.
Prevent some important naturally occurring disturbances.