ESA ESA Community Ecology 2 — Questions and Answers
Question 1: Which successional concept proposes that late-successional dominants inhibit early colonists but are eventually replaced by species tolerant of low resources?
- Facilitation model
- Inhibition model
- Tolerance model (Correct answer)
- Relay floristics
Correct answer: Tolerance model
The tolerance model holds that species later in succession can establish under conditions created by earlier species and eventually outcompete them.
Question 2: An ecological guild is defined as a group of species that:
- Occupy the same geographic range
- Exploit the same class of environmental resources in a similar way (Correct answer)
- Share the same phylogenetic lineage
- Compete directly for the same mate
Correct answer: Exploit the same class of environmental resources in a similar way
A guild groups species by functional role in resource use, regardless of taxonomic relationships.
Question 3: The competitive exclusion principle (Gause's Law) states that:
- Two species can coexist indefinitely if they compete for the same niche
- Complete competitors cannot coexist indefinitely on a single limiting resource (Correct answer)
- Competition always reduces biodiversity
- Predation prevents competitive exclusion
Correct answer: Complete competitors cannot coexist indefinitely on a single limiting resource
Gause's Law states that two species competing for the exact same limiting resource cannot stably coexist; one will be excluded.
Question 4: Which mutualistic relationship is obligate for both partners and results in a single functional organism?
- Mycorrhizae
- Lichens (Correct answer)
- Cleaner fish stations
- Pollination syndromes
Correct answer: Lichens
Lichens are an obligate symbiosis between fungi and photosynthetic algae or cyanobacteria that together form a single composite organism.
Question 5: Trophic cascade effects occur when:
- Nutrient inputs increase primary productivity
- Changes in predator abundance indirectly alter plant biomass through effects on herbivores (Correct answer)
- Species migrate between trophic levels seasonally
- Competition drives species to lower trophic positions
Correct answer: Changes in predator abundance indirectly alter plant biomass through effects on herbivores
A trophic cascade propagates indirect effects through food webs, typically with top predators controlling herbivores that in turn affect vegetation.
Question 6: In plant community ecology, the 'climax community' concept has largely been replaced by which more dynamic view?
- The steady-state equilibrium model
- The shifting mosaic and non-equilibrium paradigm (Correct answer)
- The deterministic succession model
- The super-organism model
Correct answer: The shifting mosaic and non-equilibrium paradigm
Modern ecology views communities as non-equilibrial shifting mosaics shaped by disturbance, with no single stable endpoint.
ESA ESA Community Ecology 2
Which successional concept proposes that late-successional dominants inhibit early colonists but are eventually replaced by species tolerant of low resources?