1.1.4 and 2.5.4 Thermodynamics
nutrient cycles
Two basic processes must occur in an ecosystem:
1.
A cycling of chemical elements.
2.
Flow of energy.
Energy flows
through
systems while materials circulate
around
systems.
Cycling of Chemical Elements
TRANSFERS:
normally flow through a system and involve a
change in location.
TRANSFORMATIONS:
lead to an interaction within a system
in the formation of a new end product, or involve a change of
state.
Water “hydrologic” Cycle
Precipitation
Precipitation
to ocean
Evaporation
Evaporation
From
ocean
Surface runoff
(rapid)
Ocean storage
Condensation
Transpiration
Rain clouds
Infiltration and
percolation
Transpiration
from plants
Groundwater movement (slow)
Groundwater movement (slow)
Runoff
Runoff
Surface runoff (rapid)
Surface runoff (rapid)
Precipitation
Terrestrial carbon Cycle
photosynthesis
aerobic
respiration
Terrestrial
rocks
Soil water
(dissolved
carbon)
Land food webs
producers, consumers,
decomposers, detritivores
Atmosphere
(mainly carbon dioxide)
Peat,
fossil fuels
combustion of
wood (for clearing
land; or for fuel
sedimentation
volcanic
action
death, burial, compaction
over geologic time
leaching
runoff
weathering
nitrogen Cycle
NO
3
–
in soil
Nitrogen
Fixation
by industry
for
agriculture
Fertilizers
Food Webs On
Land
NH
3
,
NH
4
+
in soil
1. Nitrification
bacteria convert
NH
4
+
to
nitrate
(NO
2
–
)
loss by
leaching
uptake by
autotrophs
excretion,
death,
decomposition
uptake by
autotrophs
Nitrogen Fixation
bacteria convert to
ammonia (NH
3
+
) ; this
dissolves to form
ammonium (NH
4
+
)
loss by
leaching
Ammonification
bacteria, fungi convert
the residues to NH
3
,
this dissolves to form
NH
4
+
2. Nitrification
bacteria convert NO
2
-
to
nitrate (NO
3
-
)
Denitrification
by bacteria
Nitrogenous Wastes,
Remains In Soil
Gaseous Nitrogen (N
2
)
In Atmosphere
NO
2
–
in soil
© 2004 Brooks/Cole
–
Thomson Learning
Phosphorous Cycle
GUANO
FERTILIZER
ROCKS
LAND
FOOD
WEBS
DISSOLVED IN
OCEAN
WATER
MARINE
FOOD
WEBS
MARINE SEDIMENTS
weathering
agriculture
uptake by
autotrophs
death,
decomposition
sedimentation
settling
out
weathering
weathering
DISSOLVED IN
SOIL WATER,
LAKES, RIVERS
uptake by
autotrophs
death,
decomposition
uplifting
over
geologic
time
uplifting
over
geologic
time
mining
mining
excretion
excretion
sulfur Cycle
Hydrogen sulfide
(H
2
S)
+
Water (H
2
O)
Sulfur dioxide (SO
2
)
and
Sulfur trioxide (SO
3
)
Dimethyl
(DMS)
Industries
Sulfuric acid
(H
2
SO
4
)
Oceans
+
Ammonia (NH
2
)
+
Oxygen (O
2
)
Ammonium sulfate
[(NH
4
)
2
SO
4
]
Animals
Plants
Sulfate salts
(SO
4
2
-
)
Hydrogen sulfide
(H
2
S)
Decaying
organisms
Sulfur
(S)
Fog and precipitation
(rain, snow)
Aerobic conditions
in soil and water
Anaerobic
conditions in
soil and water
Volcanoes
and
hot springs
Atmosphere
Flow of Energy
Thermodynamics
is the study of the energy transformations
that occur in a system.
•
It is the study of the flow of energy through nature.
•
Within a system energy cannot be re
-
used.
1
st
Law of Thermodynamics
•
States that energy can be transferred and transformed, but it CANNOT be
created nor destroyed.
•
Law of Conservation of Energy.
•
Energy of the universe is constant.
Thermal equilibrium = inputs equal outputs over a long period of time.
2
nd
Law of Thermodynamics
•
States that every transformation results in a reduction of the FREE ENERGY
(useable energy).
•
Energy transfers and transformations increase ENTROPY (disorder, randomness
or chaos).
•
Law of Entropy.
•
Energy always tends to go from a more usable (higher quality) form to a less
usable (lower quality) form.
•
You can’t get something for nothing
•
No such thing as a free lunch
•
Any conversion is less than 100% efficient and therefore some energy is lost
or wasted.
•
Usually this energy is lost in the form of
HEAT
(= random energy of
molecular movement
). We usually summarize it as respiration.
Solar
energy
Waste
heat
Chemical
energy
(photosynthesis)
Waste
heat
Waste
heat
Waste
heat
Chemical
energy
(food)
Mechanical
energy
(moving,
thinking,
living)
Only 25% of chemical “E” stored in gasoline is transformed in to motion
of the car and 75% is lost as heat!!
Without adding energy to a system, the system will break down .
Heat
Heat
Heat
Heat
Heat
10
100
1,000
10,000
Usable energy
available at
each tropic level
(in kilocalories)
Producers
(phytoplankton)
Primary
consumers
(zooplankton)
Secondary
consumers
(perch)
Tertiary
consumers
(human)
Decomposers
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