Ecosystems Knowledge-Based Download PDF

Questions

1. 1.

   Which of the following best explains why the removal of a keystone species has a disproportionately large impact on an ecosystem?

   • A) Keystone species constitute the vast majority of total biomass and primary productivity within the ecosystem.
   • B) Keystone species exert strong regulatory control over community structure and biodiversity despite their relatively low abundance or biomass.
   • C) Keystone species serve as the primary autotrophic organisms that convert solar energy into chemical energy for all trophic levels.
   • D) Keystone species are specialized decomposers that uniquely recycle all inorganic nutrients back into abiotic reservoirs.
2. 2.

   Which of the following statements correctly distinguishes gross primary productivity (GPP) from net primary productivity (NPP) in an ecosystem?

   • A) GPP is the energy accumulated in consumer biomass, whereas NPP is the total solar energy captured by autotrophs.
   • B) NPP is the total solar energy captured during photosynthesis, whereas GPP represents the energy lost as metabolic heat.
   • C) NPP represents the rate of biomass accumulation by autotrophs after subtracting the energy used for cellular respiration from GPP.
   • D) GPP and NPP are equal in mature ecosystems because autotrophic cellular respiration drops to zero at ecological climax.
3. 3.

   Which of the following best explains why food chains within ecosystems are generally limited to four or five trophic levels?

   • A) Most energy is lost as heat through metabolic processes at each successive transfer, leaving insufficient energy to support additional levels.
   • B) Top predators consume all available primary producers, directly eliminating the foundation required for higher trophic tiers.
   • C) Decomposers prevent higher levels from forming by consuming all organic matter before carnivores can access it.
   • D) Biomass accumulates at higher trophic levels until toxic concentrations naturally collapse subsequent populations.
4. 4.

   Which of the following statements correctly compares the flow of energy and the cycling of matter in an ecosystem?

   • A) Energy flows through an ecosystem in a one-way path, whereas chemical nutrients are recycled within the system.
   • B) Energy is continuously recycled by decomposers, whereas chemical nutrients are permanently lost as metabolic heat.
   • C) Both energy and nutrients cycle infinitely within the community without any exchange with the abiotic environment.
   • D) Energy flows from apex predators down to primary producers, whereas nutrients escape into the atmosphere without cycling.
5. 5.

   Which of the following best defines an ecosystem?

   • A) A group of organisms of the same species living and reproducing in a designated area
   • B) All the different interacting populations of living organisms inhabiting a specific habitat
   • C) The non-living physical and chemical components that make up a geographical environment
   • D) A biological community of interacting organisms together with the abiotic environment functioning as a unit