Page 149 - Environment: The Science Behind the Stories

• Ecological processes naturally provide services that we specialized bacteria or lightning before plants can use it.
depend on for everyday living. (pp. 134–135) (pp. 141, 144)
• Phosphorus is most abundant in sedimentary rock, with
Compare and contrast how water, carbon, nitrogen, substantial amounts in soil and the oceans. Phosphorus has
and phosphorous cycle through the environment
no appreciable atmospheric reservoir. It is a key nutrient
• A source is a reservoir that contributes more of a material for plant growth. (p. 145)
than it receives, and a sink is one that receives more than it
provides. (p. 135)
Explain how human impact is affecting biogeochemi-
• Water moves widely through the environment in the water cal cycles
cycle. (pp. 138–139)
• People are affecting Earth’s biogeochemical cycles by
• Most carbon is contained in sedimentary rock. Substantial shifting carbon from fossil fuel reservoirs into the atmos-
amounts also occur in the oceans and in soil. Carbon flux phere, shifting nitrogen from the atmosphere to the planet’s
between organisms and the atmosphere occurs via photo- surface, and depleting groundwater supplies, among other
synthesis and respiration. (pp. 139–141) impacts. (pp. 139–146)
• Nitrogen is a vital nutrient for plant growth. Most • Policy can help us address problems with nutrient pollu-
nitrogen is in the atmosphere, so it must be “fixed” by tion. (p. 146)

Testing Your Comprehension

1. What is the difference between a positive and a negative 7. What is the difference between evaporation and transpira-
feedback loop? Explain what happens when a system is tion? Give examples of how the water cycle interacts with
in dynamic equilibrium. the carbon, phosphorus, and nitrogen cycles.
2. List four ways in which humans have altered the water 8. Give a brief overview of the carbon cycle. Include the
cycle. What are the major concerns for the future? source of carbon that enters ecosystems, how it moves
3. What is the difference between an ecosystem and a through ecosystems, what it is used for, and where it is
community? ultimately deposited. What part of this cycle is believed
to contribute to global warming?
4. Describe the typical movement of energy through an eco-
system. Now describe the typical movement of matter 9. Distinguish the function performed by nitrogen-fixing
through an ecosystem. bacteria from that performed by denitrifying bacteria.
5. Explain net primary productivity. Name one ecosystem 10. How has human activity altered the carbon cycle? The
with high net primary productivity and one with low net phosphorus cycle? The nitrogen cycle? What environ-
primary productivity. mental problems have arisen from these changes?
6. Why are patches in a landscape mosaic often important
to people who are interested in conserving populations of
rare animals?

Seeking Solutions

1. Once vegetation is cleared from a riverbank, water begins 3. For a conservation biologist interested in sustaining pop-
to erode the bank away. This erosion may dislodge more ulations of the organisms below, why would it be helpful
vegetation. Would you expect this to result in a feed- to take a landscape ecology perspective? Explain your
back process? If so, which type—negative or positive? answer in each case.
Explain your answer. How might we halt or reverse this • A forest-breeding warbler that suffers poor nesting
process? success in small, fragmented forest patches
2. Consider the ecosystem(s) that surround(s) your campus. • A bighorn sheep that must move seasonally between
Describe one way in which energy flows through and mat- mountains and lowlands
ter is recycled. Now pick one type of nutrient, and briefly
describe how it moves through your ecosystem(s). Does the • A toad that lives in upland areas but travels cross-
148 landscape contain patches? Can you describe any ecotones? country to breed in localized pools each spring

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