ESA ESA Community Ecology 1 — Questions and Answers
Question 1: Which term describes the sequential change in species composition of a community over time following a disturbance that leaves soil intact?
- Primary succession
- Secondary succession (Correct answer)
- Allogenic succession
- Retrogressive succession
Correct answer: Secondary succession
Secondary succession occurs on sites where soil remains after a disturbance, allowing faster colonization than primary succession.
Question 2: The intermediate disturbance hypothesis predicts that species diversity is highest at:
- Very low disturbance frequencies
- Very high disturbance frequencies
- Intermediate disturbance frequencies (Correct answer)
- Zero disturbance
Correct answer: Intermediate disturbance frequencies
Intermediate disturbance prevents competitive exclusion by dominants while still allowing recolonization by early successional species, maximizing diversity.
Question 3: A keystone species is best defined as a species that:
- Has the highest biomass in the community
- Exerts a disproportionately large effect on community structure relative to its abundance (Correct answer)
- Is endemic to a single region
- Occupies the highest trophic level
Correct answer: Exerts a disproportionately large effect on community structure relative to its abundance
A keystone species has an ecological impact far greater than would be predicted from its abundance or biomass alone.
Question 4: Which index combines both species richness and evenness to quantify community diversity?
- Jaccard index
- Shannon-Wiener index (Correct answer)
- Whittaker's beta diversity
- Sorensen index
Correct answer: Shannon-Wiener index
The Shannon-Wiener index (H') accounts for both the number of species and the relative abundance of each species in a community.
Question 5: Interspecific competition in which one species directly harms another through toxin release is called:
- Interference competition
- Exploitative competition
- Allelopathy (Correct answer)
- Amensalism
Correct answer: Allelopathy
Allelopathy refers specifically to chemical inhibition of one plant (or microbe) by another via release of secondary metabolites.
Question 6: Beta diversity measures:
- Species diversity within a single habitat
- The change in species composition between different habitats or along environmental gradients (Correct answer)
- The total diversity of a landscape
- Genetic diversity within a population
Correct answer: The change in species composition between different habitats or along environmental gradients
Beta diversity quantifies the turnover or differentiation in species composition between two or more communities.
ESA ESA Community Ecology 1
Which term describes the sequential change in species composition of a community over time following a disturbance that leaves soil intact?