6.3.1 Nitrogen cycle

Which nitrogen cycle process is occurring when plant roots absorb ammonium ions and nitrate ions for use in making molecules such as DNA, amino acids, and proteins?

• nitrogen fixation

• nitrification

• denitrification

• ammonification

• assimilation

Which nitrogen cycle process is occurring when bacteria convert ammonium to nitrite and then into nitrate?

• nitrogen fixation

• nitrification

• denitrification

• ammonification

• assimilation

Which nitrogen cycle process is occurring when nitrogen in plant or animal protein is converted to ammonium?

• nitrogen fixation

• nitrification

• denitrification

• ammonification

• assimilation

Which of these nitrogen molecules would be present in the atmosphere?

• NH₃

• NH₄⁺

• NO₃^-

• N₂

Which of these nitrogen cycle processes converts atmospheric nitrogen to a soil form of nitrogen that is usable by plants?

• nitrogen fixation

• nitrification

• denitrification

• ammonification

• assimilation

When deciduous trees shed their leaves, specialized soil bacterial will consume the leaf material for energy and, in the process, will return some of the leaf nitrogen to the soil. What nitrogen cycle process is taking place?

• nitrogen fixation

• nitrification

• denitrification

• ammonification

• assimilation

According to this diagram, plants use nitrogen to make _________________________

• carbohydrates

• cellulose

• proteins

• unsaturated fats

What converts nitrogen gas into a usable form for plants and animals?

• bacteria

• rain

• fungi

• car exhaust

The process in which nitrogen circulates and is recycled is called

• The nitrogen cycle

• The carbon cycle

• The water cycle

• The phosphorus cycle

Organisms that need nitrogen to survive.

• only plants

• only animals

• only bacteria

• all living things