Chapter 54

Question 1

ecosystem

Answer 1

A system that includes all living organisms (biotic factors) in an area as well as its physical environment (abiotic factors) functioning together as a unit.

Question 2

soil organic matter

Answer 2

biological material in the process of decaying or decomposing, such as humus.

Question 3

humus

Answer 3

A dark-brown or black organic substance made up of decayed plant or animal matter. Humus provides nutrients for plants and increases the ability of soil to retain water.

Question 4

net primary productivity (NPP)

Answer 4

The rate at which an ecosystem accumulates energy or biomass, excluding the energy it uses for the process of respiration. This typically corresponds to the rate of photosynthesis, minus respiration by the photosynthesizers.

Question 5

pyramid of productivity

Answer 5

A graphical representation in the shape of a pyramid showing the distribution of productivity or flow of energy through the trophic levels.

Question 6

global carbon cycle

Answer 6

the circulation of carbon atoms in the biosphere as a result of photosynthetic conversion of carbon dioxide into complex organic compounds by plants, which are consumed by other organisms: the carbon returns to the atmosphere in the form of carbon dioxide

Question 7

gross primary productivity

Answer 7

the rate at which photosynthesis or chemosynthesis occurs.

Question 8

greenhouse gas

Answer 8

any of various gaseous compounds (such as carbon dioxide) that absorb infrared radiation, trap heat in the atmosphere, and contribute to the greenhouse effect.

Question 9

gross photosynthetic efficiency

Answer 9

refers to the amount of light energy plants and algae that are able to convert into chemical energy through photosynthesis.

Question 10

global nitrogen cycle

Answer 10

nitrogen is converted into various chemical forms as it circulates among the atmosphere and terrestrial and marine ecosystems. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.

Question 11

decomposer food chain

Answer 11

an ecological network of detritus, decomposers that eat detritus, and predators and parasites of the decomposer

Question 12

global water cycle

Answer 12

the movement of water among terrestrial ecosystems, the ocean and the atmosphere

Question 13

groundwater

Answer 13

any water below the land surface

Question 14

nitrogen fixation

Answer 14

the incorporation of atmospheric nitrogen into forms such as ammonia or nitrate which can be used to make organic compounds, occurs in bacteria

Question 15

biomass

Answer 15

the total mass of all organisms in a given population or geological area

Question 16

global warming

Answer 16

a sustained increase in Earth’s average surface temperature

Question 17

detritus

Answer 17

dead decaying organic matter

Question 18

biogeochemical cycles

Answer 18

the pattern of circulation of an element or molecule among living organisms and the environment

Question 19

primary decomposer

Answer 19

a decomposer that consumes detritus from plants

Question 20

reservoirs

Answer 20

areas or compartments where elements are stored for a period of time