Download Nitrogen Fixation

The Biogeochemical
Cycles
The Cycling of Chemical
Elements
in Ecosystems
• Nutrient cycling involves both the biotic
and abiotic portions of an ecosystem.
• These are called the biogeochemical
cycles.
Biological and geologic processes move
nutrients between organic and inorganic
compartments
• There are four main reservoirs of elements and
processes that transfer elements between
reservoirs.
– Reservoirs are defined by two characteristics, whether it
contains organic or inorganic materials, and whether or
not the materials are directly usable by organisms.
The Water Cycle: more of a physical process
than a chemical one.
Inorganic material not available
to organisms would be found in
A. The atmosphere
B. Fossil fuels
C. Detritus
D. Minerals or rocks
What is the term used to
describe water returning to the
atmosphere by plants?
A. excretion
B. evaporation
C. transpiration
D. vaporization
The Carbon Cycle
• Two natural processes help to cycle carbon
through the ecosystem.
– Photosynthesis; autotrophs take in CO2 and
produce organic compounds available then for
consumers.
– Cellular Respiration; both autotrophs and
heterotrophs use cellular respiration to convert
energy rich organic compounds into ATP to
power cellular functions.
The Carbon Cycle
The Carbon Cycle
Visual
Two sources of carbon dioxide
released into the atmosphere in
the carbon cycle are
A. Photosynthesis and decomposition
B. Cellular respiration and
photosynthesis
C. Combustion and transpiration
D. Cellular respiration and combustion
The Nitrogen Cycle
• Nitrogen enters ecosystems through two
natural pathways.
– Atmospheric deposition, where usable nitrogen is
added to the soil by rain.
– Nitrogen fixation, where certain bacteria convert
N2 to minerals that can eventually be used by
plants to produce nitrogenous organic
compounds.
• The direct product of Nitrogen Fixation is ammonia,
•
which picks up H+ and becomes an ion, ammonium
in the soil.
Some bacteria break down detritus and animal
waste producing ammonium through
Ammonification
• Certain bacteria convert ammonium into nitrate, a
process called Nitrification.
• Nitrate can be used by plants.
• Some bacteria take oxygen from the nitrate and
release N2 back into the atmosphere called
Denitrification.
PROCESS
WHAT IS NEEDED
(Reactants)
NITROGEN
FIXATION
Nitrogen Gas (N2)
Usable nitrogen:
Nitrates (NO3-)
made in roots of
legumes and
Ammonium (NH4+)
and in the soil.
Nitrogen fixing
bacteria in soil and
in legume roots.
AMMONIFICATION
Detritus and waste
Ammonia
Decomposers
(Bacteria and
Fungus)
NITRIFICATION
Ammonium
Nitrites (NO2-) &
NO3-
Nitrifying Bacteria
ASSIMILATION
Nitrates
Any nitrogen based Chemical reactions
compound needed
in the organism.
by plants and
animals. Nitrogen is
used to make amino
acids.
Excess nitrates
Nitrogen Gas
DENITRIFICATION
WHAT IS
PRODUCED
(Products)
WHAT DOES THE
WORK?
Denitrifying Bacteria
The Nitrogen Cycle
Visual
Two components of the
nitrogen cycle that produce
ammonia are
A. Nitrification and denitrification
B. Nitrogen fixation and nitrification
C. Nitrogen fixation and ammonification
D. Ammonification and denitrification
Animals obtain nitrogen
A. Through a mutualistic relationship
with bacteria
B. From the proteins and nucleic acids in
what they eat
C. By absorbing nitrates and ammonia
from the soil
D. By absorbing nitrogen gas from the
atmosphere
Chapter 18
Phosphorus Cycle
• In the phosphorus
cycle, phosphorus
moves from
phosphate
deposited in rock,
to the soil, to living
organisms, and
finally to the
ocean.
Decomposition rates largely determine the
rates of nutrient cycling
• The rate at which nutrients cycle in an ecosystem
depends on the rate of decomposition.
– Decomposition can take up to 50 years in the tundra,
while in the tropical forest, it occurs much faster.
• Quantities of nutrients in the soil of different
ecosystems also varies, depending on the rate of
absorption by the plants.
Nutrient cycling is strongly regulated by
vegetation
• In a terrestrial ecosystem most of the mineral
nutrients cycle within the ecosystem.
• In addition to the natural ways, nitrogen-
containing fertilizer contributes to the total
amount of nitrogen materials in ecosystems.
The End