Elements of Ecology, 8e (Smith/Smith) Chapter 21 Ecosystem Energetics 21.1 Short Answer Questions 1) The heterotrophic component of the ecosystem is often subdivided into two subsystems: consumers and Answer: decomposers Topic: Introduction to Part 2) An ecosystem with inputs of matter and energy is a(n) ecosystem Answer: open Topic: Introduction to Part 3) A(n) chemical reaction must absorb energy in order to proceed Answer: endothermic Topic: Section 21.1 4) The law of thermodynamics states that when energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further Answer: second Topic: Section 21.1 5) primary production is the total rate of photosynthesis or energy assimilated by plants Answer: Gross Topic: Section 21.2 6) The amount of accumulated organic matter found in an area at a given time is the crop biomass Answer: standing Topic: Section 21.2 7) For photosynthesis and productivity to occur, a plant must open its to take in carbon dioxide Answer: stomata Topic: Section 21.3 8) In a body of water, the depth at which the availability of light is such that the rate of photosynthesis equals the rate of respiration is called the depth Answer: compensation Topic: Section 21.4 9) Organic carbon produced within an ecosystem is termed Answer: autochthonous Topic: Section 21.5 Copyright © 2012 Pearson Education, Inc 10) Relative net primary productivity is the ratio of net primary productivity to standing Answer: biomass Topic: Section 21.6 11) Net primary is the energy available to the heterotrophic component of the ecosystem Answer: production Topic: Section 21.8 12) efficiency is the ratio of production to assimilation, which measures how efficiently the consumer incorporates assimilated energy into secondary production Answer: Production Topic: Section 21.9 13) Within any ecosystem, the two major food chains are the food chain and the grazing food chain Answer: detrital Topic: Section 21.10 21.2 Multiple-Choice Questions 1) According to the first law of thermodynamics, A) chemical reactions are exothermic B) entropy tends to increase C) potential energy tends to degrade into an unavailable form D) energy is neither created nor destroyed Answer: D Topic: Section 21.1 2) Plants assimilate energy through the process of A) decomposition B) respiration C) photosynthesis D) regeneration Answer: C Topic: Section 21.2 3) An ecologist studying productivity in a sample of grasses measures gross primary productivity as 1000 kcal / m2 / yr and autotrophic respiration as 100 kcal / m2 / yr Based on these calculations, the net primary productivity would be A) 10 kcal / m2 / yr B) 900 kcal / m2 / yr C) 1100 kcal / m2 / yr D) 10,000 kcal / m2 / yr Answer: B Topic: Section 21.2 Copyright © 2012 Pearson Education, Inc 4) Net primary productivity in an ecosystem increases as mean annual temperature A) and mean annual rainfall decrease B) decreases and mean annual rainfall increases C) increases and mean annual rainfall decreases D) and mean annual rainfall increase Answer: D Topic: Section 21.3 5) Net primary productivity is generally greatest at A) tropical latitudes near the equator B) subtropical latitudes (e.g., 25° of latitude) C) temperate latitudes (e.g., 50° of latitude) D) polar latitudes (e.g., 80° of latitude) Answer: A Topic: Section 21.3 6) In the surface waters of oceans, the two most limiting nutrients for primary productivity are A) sulfur and phosphorus B) sulfur and nitrogen C) nitrogen and iron D) nitrogen and phosphorus Answer: C Topic: Section 21.4 7) Low-moisture conditions favor allocation by a plant to A) leaves B) stems C) roots D) flowers Answer: C Topic: Section 21.6 8) Secondary production is limited primarily by A) water availability B) nutrient availability C) primary production D) light availability Answer: C Topic: Section 21.8 9) Which organism is most likely to have the highest assimilation efficiency? A) endothermic carnivore, such as a lion B) ectothermic carnivore, such as a snake C) endothermic herbivore, such as a deer D) ectothermic herbivore, such as a grasshopper Answer: A Topic: Section 21.9 Copyright © 2012 Pearson Education, Inc 10) The base of the detrital food chain is formed by A) primary producers B) decomposers C) herbivores D) dead organic matter Answer: D Topic: Section 21.10 11) In most terrestrial and many aquatic ecosystems, the food chain is the dominant pathway of energy flow A) detrital B) grazing C) consumer D) heterotroph Answer: A Topic: Section 21.12 12) Rates of herbivory are highest in A) aquatic ecosystems dominated by phytoplankton B) aquatic ecosystems dominated by vascular plants C) terrestrial ecosystems dominated by herbaceous plants D) terrestrial ecosystems dominated by woody plants Answer: A Topic: Section 21.12 13) If herbivores eat 1000 kcal of plant energy, approximately how much energy will be converted into the tissues of herbivores? A) kcal B) 10 kcal C) 100 kcal D) 1000 kcal Answer: C Topic: Section 21.13 21.3 True/False Questions 1) When a chemical reaction results in the loss of energy from the system, the reaction is exothermic Answer: TRUE Topic: Section 21.1 2) The second law of thermodynamics is valid only in a closed system, such as a living organism Answer: FALSE Topic: Section 21.1 Copyright © 2012 Pearson Education, Inc 3) Productivity may be expressed in units of energy per unit area per unit time or in units of dry organic matter per unit area per unit time Answer: TRUE Topic: Section 21.2 4) Net primary productivity cannot be measured in aquatic ecosystems Answer: FALSE Topic: Section 21.2 5) Net primary productivity is greater in areas with a long photosynthetic period than in areas with a short photosynthetic period Answer: TRUE Topic: Section 21.3 6) Net primary productivity is greater in temperate grasslands than in tropical rain forest Answer: FALSE Topic: Section 21.3 7) Net primary productivity is greater in the open ocean than along the coast Answer: FALSE Topic: Section 21.4 8) In most marine ecosystems, autochthonous inputs of organic carbon are greater than allochthonous inputs of carbon Answer: TRUE Topic: Section 21.5 9) In plants, low water availability favors the allocation of energy to the roots Answer: TRUE Topic: Section 21.6 10) In a temperate rain forest, primary productivity remains relatively constant Answer: FALSE Topic: Section 21.7 11) Primary productivity in forests often increases during the early stages of stand development and then decreases again as the forest ages and standing biomass increases Answer: TRUE Topic: Section 21.7 12) Secondary production in an ecosystem is always less than primary production Answer: TRUE Topic: Section 21.8 13) In endotherms, an increase in mass-specific metabolic rate lowers production efficiency Answer: TRUE Topic: Section 21.9 Copyright © 2012 Pearson Education, Inc 14) Primary producers form the base of all food chains Answer: FALSE Topic: Section 21.10 15) In all food chains, the flow of energy is unidirectional from the bottom to the top Answer: FALSE Topic: Section 21.10 16) Consumption efficiency is the ratio of ingestion to production Answer: TRUE Topic: Section 21.11 17) In terrestrial and shallow-water ecosystems, the grazing food chain is dominant over the detrital food chain Answer: FALSE Topic: Section 21.12 18) In stream and river ecosystems, the grazing food chain is of minor importance compared with the detrital food chain Answer: TRUE Topic: Section 21.12 19) In most ecosystems, the biomass of carnivores is greater than the biomass of producers Answer: FALSE Topic: Section 21.13 20) In all ecosystems, the biomass of primary producers is greater than the biomass of herbivores Answer: FALSE Topic: Section 21.13 21) Brian Silliman's research demonstrated that productivity in highly productive coastal salt marshes is controlled by bottom-up forces, such as physical conditions and nutrient availability Answer: FALSE Topic: Field Studies: Brian Silliman 22) Wealthy nations typically have lower rates of human appropriation of net primary productivity (HANPP) than developing nations Answer: FALSE Topic: Ecological Issues: Human Appropriation of Net Primary Productivity Copyright © 2012 Pearson Education, Inc 21.4 Essay Questions 1) Define net primary productivity and describe an experiment for how it can be measured Topic: Section 21.2 2) Describe the effects of temperature, moisture, length of photosynthetic period, and nutrient availability on net primary productivity in terrestrial ecosystems Topic: Section 21.3 3) Describe the changes that might be expected to occur in allochthonous and autochthonous sources of carbon in the energy balance of flowing water ecosystems from the smaller headwater streams to larger river systems Topic: Section 21.5 4) Explain the difference between primary production and secondary production How is secondary production affected by primary production? Topic: Section 21.8 5) What are the two main food chains of ecosystems? Which is more dominant in terrestrial ecosystems and why? Topic: Sections 21.10 and 21.12 6) Explain why energy is lost as it is transferred from one trophic level to another What are the effects of energy loss on the biomass of different trophic levels? Topic: Sections 21.1 and 21.13 7) How humans affect net primary productivity? Does the affluence of a society affect how humans appropriate net primary productivity? Topic: Ecological Issues: Human Appropriation of Net Primary Productivity Copyright © 2012 Pearson Education, Inc