52. Ecosystems

Explain why decomposition rates in a field in Nebraska would differ from the decomposition rates in a field in the Amazon. How do decomposers regulate nutrient availability in ecosystems?

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.

The web of life refers to the

a. Evolutionary relationships among living organisms

b. Connections between species in an ecosystem

c. Complicated nature of genetic variability

d. Flow of information from parent to child

e. Predatory effect of humans on the rest of the natural world

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

Why are the open oceans nutrient poor? Why are coastal areas and intertidal habitats relatively nutrient rich?

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.

Explain why it is more energy efficient (in terms of the amount of total NPP required) to eat a pound of tofu (bean curd) than a pound of hamburger.

For which chemicals are biogeochemical cycles global? Explain.

Most of the nutrients available for plant growth in an ecosystem are

a. Deposited in rain

b. Made available through the recycling of decomposers

c. Maintained within that ecosystem over time

d. B and C are correct

e. A, B, and C are correct

Use Figures 34.5C and 34.18 to predict how global warming (rapid increase in Earth's average temperature; see Module 7.14) might affect the water cycle.

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Aquatic biomes differ in levels of light, nutrients, oxygen, and water movement. These abiotic factors influence the productivity and diversity of freshwater ecosystems.

a. Productivity, roughly defined as photosynthetic output, is high in estuaries, coral reefs, and shallow ponds. Describe the abiotic factors that contribute to high productivity in these ecosystems.

b. How does extra input of nitrogen and phosphorus (for instance, by fertilizer runoff) affect the productivity of lakes and ponds? Is this nutrient input beneficial for the ecosystem? Explain.

In a model of the carbon cycle, how would you label an arrow from the atmosphere to plants?

a. cellular respiration

b. photosynthesis

c. decomposition

d. consumption

Researchers use models like the business-as-usual model to examine the possible effects of climate change on both terrestrial and aquatic ecosystems. These models are not predictions of our future, but instead allow us to make decisions now to avoid future problems. Provide examples of how society should change to reduce the impact of climate change on our oceans.

Which of the following organisms is correctly paired with a trophic level?

a. cyanobacterium—secondary consumer

b. grasshopper—primary consumer

c. zooplankton—primary producer

d. grass—decomposer