Biogeochemical Cycles

Animals and plants need ____________ to build proteins and nucleic acids.

Animals get the nitrogen they need by ____________ plants and other animals.

____________ does not cycle through the atmosphere, only on land and through plants and animals.

Plants need CO₂ to carry out the process of ____________.

Water is said to be a ____________ molecule because of the slightly negative charge of its oxygen atom and the slightly positive charges of its hydrogen atoms.

Which statement correctly describes how nitrogen in the soil returns to the atmosphere?

• A.  Soil bacteria convert nitrates into nitrogen gas.

• B.  Decomposers directly convert ammonium into nitrogen gas.

• C.  Plants assimilate nitrites and convert them into nitrogen gas.

• D.  Nitrogen-fixing bacteria in plant roots convert nitrates into nitrogen gas.

The production of ammonia by bacteria during the decay of nitrogen-containing urea describes which stage of the nitrogen cycle?

• A.  Assimilation

• B.  Nitrification

• C.  Ammonification

• D.  Denitrification

Nitrogen gas is transformed into usable compounds by

• A.  Decomposers

• B.  Nitrifying bacteria

• C.  Denitrifying bacteria

• D. Nitrogen-fixing bacteria

Which of the following statements is inaccurate with regard to carbon?

• A.  All organisms on Earth are carbon-based life forms.

• B.  Carbon dioxide is a naturally-occurring greenhouse gas.

• C.  Carbon does not cycle through the atmosphere.

• D.  Deforestation contributes to increased carbon dioxide levels.

Which of the following is a carbon sink?

• A.  Rocks and soil

• B.  The ocean

• C.  Living organisms

• D.  All of the above