Community Structure and Dynamics Flashcards
What is a community?
Assemblages of populations sharing a particular space and time
Examples include animals, microbes, and fungi in a rotting log.
Define community types.
Collections of the same groups of species that occur repeatedly in space and time.
What does community synergism refer to?
A community is more than the sum of its parts.
How does competition influence community structure?
It affects species composition.
What is the Shannon-Weiner Index used for?
To calculate species diversity.
What does the formula H = -∑ (pi) (log pi) represent?
The diversity index in the Shannon-Weiner Index.
What factors determine species diversity?
Richness and evenness.
What are the measures of dominance in a community?
- Relative dominance
- Relative density
- Relative frequency
- Importance value
What is the importance value in community structure?
Relative dominance + relative density + relative frequency.
What is trophic structure?
Food chains and food webs.
Define community dynamics.
The changing mosaic/quilt idea of communities.
What factors dictate community arrangements?
- Heterogeneity or patchiness of abiotic environment
- Ecological amplitude of each species
What are ecotones?
Gradient areas exhibiting unique ‘edge’ habitat characteristics.
Provide an example of an ecotone.
Grassland transition to woodland.
What is zonation in ecology?
Patterns of spatial variation in communities.
What are the types of succession?
- Degradative
- Allogenic
- Autogenic
What is the facilitative model of succession?
Early species modify the community to make it more suitable for succeeding species.
Describe the inhibition model of succession.
Community development depends on which species arrive first, potentially out-competing later arrivals.
What does the tolerance model suggest?
Later arrivals survive because they can tolerate lower resources.
What is a climax community?
The final, stable, self-perpetuating stage of succession.
What role does competition play at the community level?
Intraspecific competition is often greater than interspecific competition.
How can predation affect community structure?
Presence/absence and degree of predation can create gaps for colonization.
What types of disturbances exist in community ecology?
- Regular disturbances
- Catastrophes
How does disturbance relate to community diversity?
Disturbance can lead to increased gaps, resulting in a mosaic and successional sequence.
What is the relationship between disturbance and succession?
Disturbance resets the clock in succession.
What is the effect of regular disturbances on species diversity?
They tend to maintain a high diversity pattern due to prevalence of mid-successional species.
What does the term ‘gap’ refer to in community dynamics?
Patchiness/heterogeneity leading to diversity.
