Chapter 21

Question 1

Hydrologic cycle

Answer 1

the movement of water through ecosystems and atmosphere; includes evaporation, transpiration, and precipitation.

Question 2

On a global scale, precipitation ________ evaporation in terrestrial ecosystems; evaporation _______ precipitation in aquatic systems.

Answer 2

exceeds; exceeds

Question 3

In some oxygen-poor habitats (e.g., swamps), _________ is used for respiration instead of oxygen.

Answer 3

carbon

Question 4

Decomposing peat releases

Answer 4

releases methane gas, which exacerbates the problems of excessive greenhouse gases and global warming.

Question 5

Nitrogen fixation

Answer 5

the process of converting atmospheric nitrogen (N2) into forms producers can use, including ammonia (NH3) which is rapidly converted into ammonium (NH4+), and nitrate (NO3–).

Question 6

Nitrification

Answer 6

the final process in the nitrogen cycle, which converts ammonium to nitrite, and then from nitrite to nitrate:
NH4+ —-> NO2–  NO3–

Question 7

Mineralization

Answer 7

the process of breaking down organic compounds into inorganic compounds.

Question 8

Denitrification

Answer 8

the process of converting nitrates into nitrogen gas: NO3– –> NO2– —> NO (nitric oxide)

Question 9

Animals eliminate excess phosphorus by

Answer 9

excreting urine with PO43– or other phosphorus compounds that are converted to PO43– ions by phosphatizing bacteria.

Question 10

Eutrophication

Answer 10

an increase in productivity of aquatic ecosystems.

Question 11

Cultural eutrophication

Answer 11

an increase in the productivity of aquatic

ecosystems caused by human activities.

Question 12

watershed

Answer 12

Ecologists often measure rates of nutrient regeneration in a watershed, which is an area of land draining into a single stream or river.