10/2/2013

Nitrogen Cycle Questions



60. The main reservoir of N is in the air, which is about ______________ percent nitrogen gas.

61. Plants cannot assimilate nitrogen gas from the atmosphere. (true or false)

62. To be assimilated by higer plants, nitrogen must be present as a __________or __________ions.

63. A number of bacteria and certain blue green algae can convert nitrogen gas to the ammonium form, a process called nitrogen _________.

64. The bacteria have mutualistic relationship with the ___________ family of plants.

65. Once fixed, nitrogen may be passed down food chains, excreted as ________________, and recycle as the mineral nutrient called __________.

66. Nitrogen eventually  returns back to the atmosphere because certain bacteria convert the nitrate and ammonia compounds back to ___________.

Write a one paragraph essay explaining how earthworms cycle nitrogen back into the ecosystem.