OpenStax Biology 2e Instructor Answer Guide
Biology 2e
Unit 8: Ecology
Chapter 46: Ecosystems
Visual Connection Questions
1. Why do you think the value for gross productivity of the primary producers is the same as the
value for total heat and respiration (20,810 kcal/m2 /yr)?
According to the first law of thermodynamics, energy can neither be created nor destroyed.
Eventually, all energy consumed by living systems is lost as heat or used for respiration, and the
total energy output of the system must equal the energy that went into it.
2. Pyramids depicting the number of organisms or biomass may be inverted, upright, or even
diamond-shaped. Energy pyramids, however, are always upright. Why?
Pyramids of organisms may be inverted or diamond-shaped because a large organism, such as a
tree, can sustain many smaller organisms. Likewise, a low biomass of organisms can sustain a
, OpenStax Biology 2e Instructor Answer Guide
larger biomass at the next trophic level because the organisms reproduce rapidly and thus
supply continuous nourishment. Energy pyramids, however, must always be upright because of
the laws of thermodynamics. The first law of thermodynamics states that energy can neither be
created nor destroyed; thus, each trophic level must acquire energy from the trophic level
below. The second law of thermodynamics states that, during the transfer of energy, some
energy is always lost as heat; thus, less energy is available at each higher trophic level.
3. Which of the following statements about the nitrogen cycle is false?
c. Nitrification by bacteria converts nitrates (NO3−) to nitrites (NO2−).
Review Questions
4. The ability of an ecosystem to return to its equilibrium state after an environmental
disturbance is called ________.
d. resilience
5. A re-created ecosystem in a laboratory environment is known as a ________.
c. microcosm
6. Decomposers are associated with which class of food web?
b. detrital
7. The primary producers in an ocean grazing food web are usually ________.
d. phytoplankton
8. What term describes the use of mathematical equations in the modeling of linear aspects of
ecosystems?
a. analytical modeling
Biology 2e
Unit 8: Ecology
Chapter 46: Ecosystems
Visual Connection Questions
1. Why do you think the value for gross productivity of the primary producers is the same as the
value for total heat and respiration (20,810 kcal/m2 /yr)?
According to the first law of thermodynamics, energy can neither be created nor destroyed.
Eventually, all energy consumed by living systems is lost as heat or used for respiration, and the
total energy output of the system must equal the energy that went into it.
2. Pyramids depicting the number of organisms or biomass may be inverted, upright, or even
diamond-shaped. Energy pyramids, however, are always upright. Why?
Pyramids of organisms may be inverted or diamond-shaped because a large organism, such as a
tree, can sustain many smaller organisms. Likewise, a low biomass of organisms can sustain a
, OpenStax Biology 2e Instructor Answer Guide
larger biomass at the next trophic level because the organisms reproduce rapidly and thus
supply continuous nourishment. Energy pyramids, however, must always be upright because of
the laws of thermodynamics. The first law of thermodynamics states that energy can neither be
created nor destroyed; thus, each trophic level must acquire energy from the trophic level
below. The second law of thermodynamics states that, during the transfer of energy, some
energy is always lost as heat; thus, less energy is available at each higher trophic level.
3. Which of the following statements about the nitrogen cycle is false?
c. Nitrification by bacteria converts nitrates (NO3−) to nitrites (NO2−).
Review Questions
4. The ability of an ecosystem to return to its equilibrium state after an environmental
disturbance is called ________.
d. resilience
5. A re-created ecosystem in a laboratory environment is known as a ________.
c. microcosm
6. Decomposers are associated with which class of food web?
b. detrital
7. The primary producers in an ocean grazing food web are usually ________.
d. phytoplankton
8. What term describes the use of mathematical equations in the modeling of linear aspects of
ecosystems?
a. analytical modeling
