1.1.4 and 2.5.4 Thermodynaics and Nurtient Cycling

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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