Keystone species Knowledge-Based Download PDF

Questions

1. 1.

   In many tropical forest communities, fig trees (genus Ficus) are recognized as keystone species because they provide which critical ecological function?

   • A) They outcompete invasive flora by rapidly absorbing limiting soil macronutrients.
   • B) They harbor symbiotic bacteria that fix atmospheric nitrogen to enrich nutrient-poor soils.
   • C) They produce abundant fruit during seasons when other food resources are scarce, sustaining diverse frugivore populations.
   • D) They synthesize toxic secondary metabolites that deter generalist herbivores from consuming understory vegetation.
2. 2.

   While many recognized keystone species are apex predators, organisms such as the North American beaver (Castor canadensis) also function as keystone species primarily through which mechanism?

   • A) Producing the vast majority of biomass and chemical energy available to primary consumers
   • B) Modifying the physical landscape to create novel aquatic habitats that sustain diverse ecological assemblages
   • C) Outcompeting herbaceous herbivores to dominate the total abundance of the temperate forest
   • D) Functioning as obligate mutualistic pollinators essential for the reproductive success of all riparian trees
3. 3.

   What is the most likely consequence of removing a keystone predator, such as the sea star Pisaster ochraceus, from its marine intertidal community?

   • A) Primary productivity immediately doubles as producer species proliferate without disturbance.
   • B) Overall species richness increases because subordinate prey species are freed from top-down predation pressure.
   • C) Overall species richness decreases because competitively dominant prey species outcompete other species for space.
   • D) The community structure remains stable because functionally redundant predators immediately compensate for its absence.
4. 4.

   How does a keystone species primarily differ from a dominant species in an ecological community?

   • A) A keystone species provides the greatest total biomass and physical habitat structure, whereas a dominant species exerts influence solely through mutualistic interactions.
   • B) A keystone species exerts an ecological influence disproportionately large relative to its abundance, whereas a dominant species exerts influence primarily due to its high abundance or biomass.
   • C) A keystone species occupies the lowest trophic level in a food web, whereas a dominant species always functions as a top apex predator.
   • D) A keystone species prevents disturbance events from occurring, whereas a dominant species increases the rate of natural ecological succession.
5. 5.

   Which statement best describes the ecological role of a keystone species within a community?

   • A) It exerts strong regulation over community structure and diversity disproportionately relative to its biomass or abundance.
   • B) It possesses the largest total biomass and greatest numerical abundance among all organisms in the habitat.
   • C) It serves as the primary pioneer organism responsible for breaking down bare rock during primary succession.
   • D) It maintains the highest reproductive rate and shortest generation time among consumer populations in the food web.