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

Precipitationto ocean

Evaporation

EvaporationFromocean

Surface runoff(rapid)

Ocean storage

Condensation

Transpiration

Rain clouds

Infiltration andpercolation

Transpirationfrom plants

Groundwater movement (slow)

Groundwater movement (slow)

RunoffRunoff

Surface runoff (rapid)Surface runoff (rapid)

Precipitation

Terrestrial carbon Cycle

photosynthesis

aerobic respiration

Terrestrialrocks

Soil water(dissolved carbon)

Land food websproducers, 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

NO3 –

in soil

Nitrogen Fixation

by industry for

agriculture

Fertilizers

Food Webs On Land

NH3, NH4

+

in soil1. Nitrificationbacteria convert

NH4+ to nitrate

(NO2–)

loss by leaching

uptake by autotroph

s

excretion, death,

decomposition

uptake by autotroph

s

Nitrogen Fixationbacteria convert to

ammonia (NH3+) ; this

dissolves to form

ammonium (NH4+)

loss by leaching

Ammonificationbacteria, fungi convert

the residues to NH3 ,

this dissolves to form

NH4+

2. Nitrification

bacteria convert NO2-

to nitrate (NO3-)

Denitrificationby bacteria

Nitrogenous Wastes, Remains In Soil

Gaseous Nitrogen

(N2)

In Atmosphere

NO2 –

in soil

© 2004 Brooks/Cole – Thomson Learning

Phosphorous Cycle

GUANO

FERTILIZER

ROCKS

LAND FOO

D WEB

S

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

weathering

agriculture

uptake by autotroph

s

death, decompositio

nsedimentati

on

settling out

weathering

weathering DISSOLVED IN SOIL WATER,

LAKES, RIVERS

uptake by autotroph

s

death, decompositio

n

uplifting over

geologic time

uplifting over

geologic time

miningmining

excretion

excretion

sulfur Cycle

Hydrogen sulfide(H2S)

+Water (H2O)

Sulfur dioxide (SO2)and

Sulfur trioxide (SO3)

Dimethyl(DMS) Industries

Sulfuric acid(H2SO4)

Oceans

+Ammonia (NH2)

+Oxygen (O2)

Ammonium sulfate[(NH4)2SO4]

Animals

Plants

Sulfate salts(SO4

2-)

Hydrogen sulfide(H2S)

Decayingorganisms

Sulfur(S)

Fog and precipitation(rain, snow)

Aerobic conditionsin soil and water

Anaerobicconditions in

soil and water

Volcanoesand

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.

1st 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.

2nd 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

Second Law of Thermodynamics

•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.

Solarenergy

Wasteheat

Chemicalenergy

(photosynthesis)

Wasteheat

Wasteheat

Wasteheat

Chemicalenergy(food)

Mechanicalenergy(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

10,000Usable energy

available ateach tropic level(in kilocalories)

Producers(phytoplankton)

Primaryconsumers

(zooplankton)

Secondaryconsumers

(perch)

Tertiaryconsumers(human)

Decomposers