Natural Cycles

Which of the following is NOT one of the elements most abundant in living things?

• carbon

• helium

• oxygen

• nitrogen

A pollutant released into the atmosphere is ________.

• an emission

• a nodule

• acid precipitation

• photochemical smog

Releasing nitrogen from the soil back into the atmosphere is called __________.

• nitrogen fixation

• cellular respiration

• denitrification

• photosynthesis

Converting nitrogen in the atmosphere into a form that can be used by plants is called __________.

• nitrogen fixation

• cellular respiration

• denitrification

• photosynthesis

Which of the following hosts nitrogen-fixing bacteria in nodules on its roots?

• a decomposer

• a consumer

• an emission

• a legume

The process in cells by which oxygen and glucose are used to produce energy and carbon dioxide is called __________.

• nitrogen fixation

• cellular respiration

• denitrification

• photosynthesis

Which process describes how plants make sugar from sunlight, water, and carbon dioxide?

• nitrogen fixation

• cellular respiration

• denitrification

• photosynthesis

Air pollution can be caused by burning too many __________ .

• emissions

• fossil fuels

• nodules

• legumes

When precipitation gathers into a body of water, it is called __________.

• runoff

• collection

• acid precipitation

• photochemical smog

The precipitation that flows over the surface of soil is _________.

• runoff

• photochemical smog

• biogeochemical cycle

• nodule