Biogeochemical Cycles (Nitrogen Cycle) Flashcards
It refers to the
transference and
conversion of nitrogen
across many forms.
Both organisms and
natural processes (like
lightning) play a role in
the _____.
nitrogen cycle
Steps of the Nitrogen Cycle
_____
atmospheric to usable nitrogen
______
ammonia/ammonium to
nitrite/nitrates (by bacteria)
______
nitrogen releases as ammonia
after decomposition
______
nitrogen returns to the
atmosphere
Nitrogen Fixation
Nitrification
Ammonification
Denitrification
______ is the process of converting atmospheric nitrogen (N2) into ammonia (NH3) or other nitrogeneous compounds.
Nitrogen fixation
The _____ operates
through five major locations
where nitrogen is stored or
cycled:
1) Atmosphere
2) Terrestrial Biosphere
3) Aquatic Ecosystem
4) Living Organisms
5) Earth’s Crust
nitrogen cycle
The Nitrogen Cycle
_____
Role: The atmosphere is the largest
reservoir of nitrogen, containing about
78% nitrogen gas (N2). However, this
form of nitrogen is largely inert and
cannot be directly used by most living
organisms.
Significance: Nitrogen must be fixed
into a biologically usable form (like
ammonia or nitrates) through processes
like nitrogen fixation before it can enter
the terrestrial and aquatic ecosystems.
A. Atmosphere
The Nitrogen Cycle
_____
Role: Soil contains nitrogen in various
forms, such as ammonium (NH4+), nitrate
(NO3−), and organic nitrogen compounds.
Plants absorb these forms of nitrogen to
build proteins, nucleic acids, and other
molecules essential for life.
Significance: This is where nitrogen is
incorporated into the food chain,
supporting plant growth and,
subsequently, the herbivores and
carnivores that consume them.
B. Terrestrial Atmosphere
The Nitrogen Cycle
_____
Role: Nitrogen is cycled through aquatic
systems via runoff, leaching, and
atmospheric deposition. It is present in
dissolved forms like ammonium, nitrite,
and nitrate, which are used by aquatic
plants and algae.
Significance: Aquatic ecosystems are
critical in the global nitrogen cycle,
particularly in regions where nitrogen
runoff can cause eutrophication, leading to
algal blooms and oxygen depletion.
C. Aquatic Ecosystem
_____ is the process by which a body of water becomes overly enriched with nutrients, particularly
nitrogen and phosphorus, leading to excessive growth of algae and other aquatic plants.
Eutrophication
The Nitrogen Cycle
___
Role: Nitrogen is stored in the bodies of
living organisms as part of proteins, nucleic
acids, and other organic compounds. It
moves through the food web as organisms
consume plants and other animals.
Significance: The assimilation and
decomposition of nitrogen in living organisms
are crucial for recycling nitrogen back into the
soil and atmosphere.
D. Living Organisms (Plants,
Animals, and Microbes)
The Nitrogen Cycle
_____
Role: Nitrogen is also stored in the Earth’s
crust in the form of organic matter trapped in
sediments and rocks. Over geological time,
these can be released back into the
environment through weathering, volcanic
activity, and other geological processes.
Significance: Although nitrogen in the
Earth’s crust is less actively cycled than in
other locations, it represents a long-term
storage that can contribute to the nitrogen
cycle over extended periods.
E. Earth’s Crust
Role: Nitrogen is also stored in the Earth’s
crust in the form of organic matter trapped in
sediments and rocks. Over geological time,
these can be released back into the
environment through weathering, volcanic
activity, and other geological processes.
Significance: Although nitrogen in the
Earth’s crust is less actively cycled than in
other locations, it represents a long-term
storage that can contribute to the nitrogen
cycle over extended periods.
______ transfer elements and
compounds between the four spheres.
The biogeochemical cycles
____ are
important biogeochemical processes that describe
how the substance is transported through each
sphere.
Water, carbon, and the nitrogen cycle
The movement of
water from the ocean
to the atmosphere to
land and back to the
ocean is called the
water or ______.
hydrologic
cycle
