Ecosystems and Restoration Ecology

Explain why it is too narrow to define the biodiversity crisis as simply a loss of species.

Identify the four main threats to biodiversity and explain how each damages diversity.

The discipline that applies ecological principles to returning degraded ecosystems to a more natural state is known as

(A) restoration ecology.

(B) thermodynamics.

(C) eutrophication.

(D) biogeochemistry.

Imagine two populations of a fish species, one in the Mediterranean Sea and one in the Caribbean Sea. Now imagine two scenarios: (1) The populations breed separately, and (2) adults of both populations migrate yearly to the North Atlantic to interbreed. Which scenario would result in a greater loss of genetic diversity if the Mediterranean population were harvested to extinction? Explain your answer.

Nitrifying bacteria participate in the nitrogen cycle mainly by

(A) converting nitrogen gas to ammonia.

(B) releasing ammonium from organic compounds, thus

returning it to the soil.

(C) converting ammonium to nitrate, which plants absorb.

(D) incorporating nitrogen into amino acids and organic

compounds.

Which of the following has the greatest effect on the rate of chemical cycling in an ecosystem?

(A) the rate of decomposition in the ecosystem

(B) the production efficiency of the ecosystem’s consumers

(C) the trophic efficiency of the ecosystem

(D) the location of the nutrient reservoirs in the ecosystem

The Hubbard Brook watershed deforestation experiment yielded all of the following results except which of the following?

(A) Most minerals were recycled within a forest ecosystem.

(B) Calcium levels remained high in the soil of deforested areas.

(C) Deforestation increased water runoff.

(D) The nitrate concentration in waters draining the deforested area became dangerously high.

Which of the following would be considered an example of bioremediation?

(A) adding nitrogen-fixing microorganisms to a degraded ecosystem to increase nitrogen availability

(B) using a bulldozer to regrade a strip mine

(C) reconfiguring the channel of a river

(D) adding seeds of a chromium-accumulating plant to soil contaminated by chromium

If you applied a fungicide to a cornfield, what would you expect to happen to the rate of decomposition and net ecosystem production (NEP)?

(A) Both decomposition rate and NEP would decrease.

(B) Neither would change.

(C) Decomposition rate would increase and NEP would decrease.

(D) Decomposition rate would decrease and NEP would increase.

(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: 

• ocean evaporation, 425 km3 
• ocean evaporation that returns to the ocean as precipitation, 385 km3
• ocean evaporation that falls as precipitation on land, 40 km3
• evapotranspiration from plants and soil that falls as precipitation on land, 70 km3 
• runoff to the oceans, 40 km3 

(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?

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.

Using two neighboring ponds in a forest as your study site, design a controlled experiment to measure the effect of falling leaves on net primary production in a pond.

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?

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.

Why is the transfer of energy in an ecosystem referred to as energy flow, not energy cycling?

You are studying nitrogen cycling on the Serengeti Plain in Africa. During your experiment, a herd of migrating wildebeests grazes through your study plot. What would you need to know to measure their effect on nitrogen balance in the plot?

Use the second law of thermodynamics to explain why an ecosystem’s energy supply must be continually replenished.

Why is only a small portion of the solar energy that strikes Earth’s atmosphere stored by primary producers?

How can ecologists experimentally determine the factor that limits primary production in an ecosystem?

Suppose a forest was heavily burned by a wildfire. Predict how the NEP of this forest would change over time.

Explain how nitrogen and phosphorus, the nutrients that most often limit primary production, are necessary for the Calvin cycle to function in photosynthesis (see Concept 10.3).

What percentage of the solar energy that reaches the marsh is incorporated into gross primary production? Into net primary production?

How much energy is lost by primary producers as respiration in this ecosystem? How much is lost as respiration by the insect population?

If all of the detritus leaving the marsh is plant material, what percentage of all net primary production leaves the marsh as detritus each year?

If an insect that eats plant seeds containing 100 J of energy uses 30 J of that energy for respiration and excretes 50 J in its feces, what is the insect’s net secondary production? What is its production efficiency?

Tobacco leaves contain nicotine, a poisonous compound that is energetically expensive for the plant to make. What advantage might the plant gain by using some of its resources to produce nicotine?

Detritivores are consumers that obtain their energy from detritus. How many joules of energy are potentially available to detritivores in the ecosystem represented in Figure 55.10?

Why is nutrient availability in a tropical rain forest particularly vulnerable to logging?

For each of the four biogeochemical cycles in Figure 55.14, draw a simple diagram that shows one possible path for an atom of that chemical from abiotic to biotic reservoirs and back.

Why does deforestation of a watershed increase the concentration of nitrates in streams draining the watershed?

Identify the main goal of restoration ecology.

In what way is the Kissimmee River project a more complete ecological restoration than the Maungatautari project (see Figure 55.17)?

Which of the following organisms is incorrectly paired with its trophic level?

(A) cyanobacterium—primary producer

(B) grasshopper—primary consumer

(C) zooplankton—primary producer

(D) fungus—detritivore

Which of these ecosystems has the lowest net primary production per square meter?

(A) a salt marsh

(B) an open ocean

(C) a coral reef

(D) a tropical rain forest