Chapter 54 Key Terms

Question 1

actual evapotranspiration

Answer 1

The amount of water annually transpired by plants and evaporated from a landscape, usually measured in millimeters.

Question 2

biogeochemical cycle

Answer 2

Any of the various nutrient circuits, which involve both biotic and abiotic components of ecosystems.

Question 3

biological magnification

Answer 3

A trophic process in which retained substances become more concentrated with each link in the food chain.

Question 4

critical load

Answer 4

The amount of added nutrient, usually nitrogen or phosphorus, that can be absorbed by plants without damaging ecosystem integrity.

Question 5

decomposer

Answer 5

Any of the saprotrophic fungi and bacteria that absorb nutrients from nonliving organic material such as corpses, fallen plant material, and the wastes of living organisms, and convert them into inorganic forms.

Question 6

detritivore

Answer 6

A consumer that derives its energy from nonliving organic material; a decomposer.

Question 7

detritus

Answer 7

Dead organic matter.

Question 8

ecosystem

Answer 8

All the organisms in a given area as well as the abiotic factors with which they interact; a community and its physical environment.

Question 9

eutrophication

Answer 9

A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae. Cultural eutrophication refers to situations where the nutrients added to the water body originate mainly from human sources, such as agricultural drainage or sewage.

Question 10

greenhouse effect

Answer 10

The warming of planet Earth due to the atmospheric accumulation of carbon dioxide, which absorbs infrared radiation and slows its escape from the irradiated Earth.

Question 11

green-world hypothesis

Answer 11

The conjecture that terrestrial herbivores consume relatively little plant biomass because they are held in check by a variety of factors, including predators, parasites, and disease.

Question 12

gross primary production (GPP)

Answer 12

The total primary production of an ecosystem.

Question 13

limiting nutrient

Answer 13

An element that must be added for production to increase in a particular area.

Question 14

net primary production (NPP)

Answer 14

The gross primary production of an ecosystem minus the energy used by the producers for respiration.

Question 15

primary consumer

Answer 15

An herbivore; an organism in the trophic level of an ecosystem that eats plants or algae.

Question 16

primary producer

Answer 16

An autotroph, usually a photosynthetic organism. Collectively, autotrophs make up the trophic level of an ecosystem that ultimately supports all other levels.

Question 17

primary production

Answer 17

The amount of light energy converted to chemical energy (organic compounds) by autotrophs in an ecosystem during a given time period.

Question 18

production efficiency

Answer 18

The fraction of food energy that is not used for respiration.

Question 19

secondary consumer

Answer 19

A member of the trophic level of an ecosystem consisting of carnivores that eat herbivores.

Question 20

secondary production

Answer 20

The amount of chemical energy in consumers’ food that is converted to their own new biomass during a given time period.

Question 21

tertiary consumer

Answer 21

A member of the trophic level of an ecosystem consisting of carnivores that eat mainly other carnivores.

Question 22

trophic efficiency

Answer 22

The percentage of production transferred from one trophic level to the next.

Question 23

turnover time

Answer 23

The time required to replace the standing crop of a population or group of populations (for example, of phytoplankton), calculated as the ratio of standing crop to production.