Test 3 Quiz 2 Flashcards
Define community
A group of interacting plants and animals living in a given area in the same period of time
What two things make up community diversity?
species richness & evenness
Richness= the amount of species in an environment
Evenness= measure of the relative abundance number of each species (abundance is # of individuals from that species divided by total # of individuals)
What are the two markers of community productivity?
Biomass: Weight of living materials, dry weight per unit area
Diversity: Richness and evenness
Define standing crop biomass
Total amount of biomass per unit area in a given period of time
Describe the Shannon Index of Biodiversity. Does it consider richness, evenness, or both?
Find the proportion of each species, find natural log of proportion, then multiply proportion by natural log, sum for all species and multiply by -1 (bigger number wins).
Considers both richness and evenness
Describe the coefficient of community. Does it consider richness, evenness, or both?
For comparison of two communities → Multiply 2 by the number of species common to both, then divide by the sum of the number of species in both communities (higher is better).
Considers only richness.
Describe percentage similarity. Does it consider richness, evenness, or both?
Find all the species common to both. Sum up the lowest percentages for each species.Ex: Community 1 has 13% abundance of species A and 45% abundance of species B and Community 2 has 23% abundance of species A and 39% abundance of species B. Percentage similarity is equal to 13+39
Considers relative abundance (evenness) only.
Define dominance in relation to communities
The dominant species in a community can be determined by biomass or abundance. Each method may yield different results.
Define keystone species
A species that has disproportionate influence over community structure and functions. Removal will negatively affect many other species, causing a great loss in diversity.
Give an example of a keystone species providing habitat
The coral Oculina arbuscula provides a habitat for over 300 species of invertebrates, many of which complete most of their life cycle inside the coral.
Give an example of a keystone species feeding behavior
African elephants are destructive feeders that feed mainly on browse. They reduce tree and shrub density, favoring growth and reproduction of grasses.
Define edge
The place where two or more vegetation communities meet (distinct border)
Define ecotone
The place where two communities meet and interact (gradual transition)
Define edge effect
The variety and abundance of species is often better in and around ecotones and edges
Define ecological island
An isolated habitat or area
State the MacArthur-Wilson Island Equilibrium Theory
he number of species of a given taxon established on an (ecological) island represents a dynamic equilibrium between the immigration rate of new colonizing species and the extinction rate of previously established colonizing species
What are the factors determining immigration and extinction rate? How do the rates change as number of species increases?
size of island and distance from continent
Immigration- Start high, end low
Extinction- Start low, end high
As Number of Species Increases
Define succession
Temporal variation in community structure at a given location
Define and describe early/initial successional species (include selection type)
The initial colonists or pioneer species
Often Have: High growth rates, smaller size, high degree of dispersal and colonization, high rates of per capita population growth, r-selection
Define and describe late successional species (include selection type)
Arrive later
Often Have: Longer lifespans, larger size, lower rates of dispersal and colonization, lower rates of per capita population growth, k-selection
Define primary succession
Occurs at a location that was not previously occupied by a community; a newly exposed surface
Define secondary succession
Occurs at a location that was previously occupied by a community and then underwent a disturbance that removed all or part of the existing community
-can include a natural disaster or a farmer abandoning his field
Define autogenic
Self-generated environmental change; the result of the presence and activities of organisms within the community. Example: Changing vertical light profile through succession.
Define allogenic
Environmental change governed by physical (not biological) processes (Ex: temperature declines over elevation)
Describe the change in species diversity in succession
Diversity does not always increase over time
Define a climax forest
A stable end forest that perpetuates itself under prevailing environmental conditions. Needs a fire to rejuvenate its ecological functions.
Define crown fire
Spread quickly, moving through the branches
Define ground fire
Start from the ground up, burn through everything
What are some lumbering-associated social and economical issues?
Use of the income to benefit locals
Impact on nutrients
Road construction
Potential erosion related to lumber transportation