Chapter 55

Which of the following organisms is incorrectly paired with its trophic level? \begin{equation}\begin{array}{l}{\text { (A) cyanobacterium-primary producer }} \\ {\text { (B) grasshopper-primary consumer }} \\ {\text { (C) zooplankton-primary producer }} \\ {\text { (D) fungus-detritivore }}\end{array}\end{equation}

Which of these ecosystems has the lowest net primary production per square meter? $$\begin{array}{l}{\text { (A) a salt marsh }} \\ {\text { (B) an open ocean }} \\ {\text { (C) a coral reef }} \\ {\text { (D) a tropical rain forest }}\end{array}$$

The discipline that applies ecological principles to returning degraded ecosystems to a more natural state is known as \begin{equation}\begin{array}{l}{\text { (A) restoration ecology. }} \\\ {\text { (B) thermodynamics. }} \\ {\text { (C) eutrophication. }} \\ {\text { (D) biogeochemistry. }}\end{array}\end{equation}

Nitrifying bacteria participate in the nitrogen cycle mainly by \begin{equation}\begin{array}{l}{\text { (A) converting nitrogen gas to ammonia. }} \\ {\text { (B) releasing ammonium from organic compounds, thus }} \\ {\text { returning it to the soll. }} \\ {\text { (C) converting ammonium to nitrate, which plants absorb. }} \\ {\text { (D) incorporating nitrogen into amino acids and organic }}\end{array}\end{equation}

Which of the following has the greatest effect on the rate of chemical cycling in an ecosystem? \begin{equation}\begin{array}{l}{\text { (A) the rate of decomposition in the ecosystem }} \\ {\text { (B) the production efficiency of the ecosystem's consumers }} \\ {\text { (C) the trophic efficiency of the ecosystem }} \\\ {\text { (D) the location of the nutrient reservoirs in the ecosystem }}\end{array}\end{equation}

The Hubbard Brook watershed deforestation experiment yielded all of the following results except which of the following? \begin{equation}\begin{array}{l}{\text { (A) Most minerals were recycled within a forest ecosystem. }} \\ {\text { (B) Calcium levels remained high in the soll of deforested }} \\ {\text { areas. }} \\ {\text { (C) Deforestation increased water runoff. }} \\ {\text { (D) The nitrate concentration in waters draining the deforested }} \\ {\text { area became dangerously high. }}\end{array}\end{equation}

Which of the following would be considered an example of bioremediation? \begin{equation} \begin{array}{l}{\text { (A) adding nitrogen-fixing microorganisms to a degraded }} \\ {\text { ecosystem to increase nitrogen availability }} \\\ {\text { (B) using a bulldozer to regrade a strip mine }} \\ {\text { (C) reconfiguring the channel of a river }} \\ {\text { (D) adding seeds of a chromium-accumulating plant to soil }} \\ {\text { contaminated by chromium }}\end{array}\end{equation}

DRAW IT (a) Draw a simplified global water cycle showing ocean, land, atmosphere, and runoff from the land to the ocean. Label your drawing with these annual water fluxes: \begin{equation} \begin{array}{l}{\text { ocean evaporation, } 425 \mathrm{km}^{3}} \\ {\text { ocean evaporation that returns to the ocean as precipitation, }} \\ {385 \mathrm{km}^{3}}\\\\{\text { ocean evaporation that falls as precipitation on land, } 40 \mathrm{km}^{3}} \\ {\text { evapotranspiration from plants and soil that falls as precipi- }} \\ {\text { tation on land, } 70 \mathrm{km}^{3}}\\\ {\text { runoff to the oceans, } 40 \mathrm{km}^{3}}\end{array} \end{equation} (b) What is the ratio of ocean evaporation that falls as precipitation on land compared with runoff from land to the oceans? (c) How would this ratio change during an ice age, and why?

EVOLUTION CONNECTION Some biologists have suggested that ecosystems are emergent, "living" systems capable of evolving. One manifestation of this idea is environmentalist James Lovelock's Gaia hypothesis, which views Earth itself as a living, homeostatic entity \(-\) a kind of superorganism. Are ecosystems capable of evolving? If so, would this be a form of Darwinian evolution? Why or why not? Explain.

WRITE ABOUT A THEME: ENERGY AND MATTER Decomposition typically occurs quickly in moist tropical forests. However, waterlogging in the soil of some moist tropical forests results over time in a buildup of organic matter called "peat." In a short essay \((100-150\) words), discuss the relationship of net primary production, net ecosystem production, and decomposition for such an ecosystem. Are NPP and NEP likely to be positive? What do you think would happen to NEP if a landowner drained the water from a tropical peatland, exposing the organic matter to air?

SYNTHESIZE YOUR KNOWLEDGE This dung beetle (genus Scarabaeus) is burying a ball of dung it has collected from a large mammalian herbivore in Kenya. Explain why this process is important for the cycling of nutrients and for primary production.