Second Law of Thermodynamics (Law of Energy Degradation)

thoughtgreenpepperMechanics

Oct 27, 2013 (3 years and 9 months ago)

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Second Law of Thermodynamics (Law of Energy Degradation)


-

in all conversions of heat energy to work, some of the energy is degraded to a


more dispersed & less useful form (usually heat); no conversion is 100%


-

heat always flows spontaneously fro
m hot to cold


-

any system & its surroundings as a whole spontaneously tend toward increasing


randomness or disorder (entropy = measure of disorder or randomness)


Food Chain

-

sequence of transfers of energy in the form of food from organisms in on
e


trophic

(feeding) level to organisms in another, when one eats or decomposes another

-

only ~10% of the high quality chemical energy available at one trophic level
can be
transferred to the next; this is known as the
10% Rule

& is due to the 2nd Law o
f
Thermodynamics which states that in all conversions of heat energy to work, some of the
energy is degraded to a more dispersed & less useful form. So, the shorter the food chain,
the less loss of usable energy &, in addition, the
biomass

(total combined
weight of any
group of organisms) decreases at higher trophic levels


Food Web

-

complex, interlocking series of food chains


B
iogeochemical
C
ycles


hydrologic (water
-

hydrogen & oxygen).

gaseous (carbon, oxygen, nitrogen),

sedimentary (phosphorus, sulfu
r, etc.)


Hydrologic

-

water comes down to the Earth via precipitation. It then either enters the ground to
become groundwater or stays on the surface to become surface water. Either way it eventually
enters the oceans & lakes to be returned to the atmosp
here via evaporation. Some of the water is
taken up by the plants, which in turn return

the water through the process of transpiration


Carbon
-
Oxygen

-

carbon enters the atmosphere by respiration, volcanic eruptions, burning of
fossil fuels, etc. Plants
use sunlight & incorporate the CO
2

via photosynthesis into organic
molecules which are used as food by animals


Nitrogen

-

is found in the bodies of organisms as dissolved gas & dissolved organic matter.It is
bound with free oxygen or hydrogen into usable

chemical forms by specialized organisms. It
enters the ocean through rivers & precipitation. After being assimilated by plants, the nitrogen is
recycled when animals eat them & excrete ammonium & urea


Phosphorus

-

is weathered from rock, washed into the
rivers & ends up in the ocean. Plants
absorb it & when they are eaten it gets passed to the animals. Eventually it returns to the soil as
waste & decay products.


Sulfur

-

enters the atmosphere from natural sources ; returns to the Earth via precipitation

where
it is taken up by plants & passed to the animals. Eventually it returns to the soil as waste & decay
products



Ecosystems are dynamic & not static systems; they are constantly changing


Ecological Niche

-

a species total structural & functional rol
e in an ecosystem


-

what a particular species does in the ecosystem & how it responds to &




modifies its biotic & abiotic environment


-

do not confuse with
habitat
(location where an organism lives &
grows)


-

habitat & niche are analogous to address & occupation/life
-
style


Competitive Exclusion Principle

-

no 2 species in the same ecosystem can occupy exactly


the same ecological niche indefinitely


The number of “niche
-
spac
es” available for a species in a particular ecosystem determines its
carrying capacity

-

maximum number of individuals of each species that can live in a particular
ecosystem


Ecological Succession

-

repeated replacement of one kind of natural community of


organisms with a different natural community over time


Primary Succession

-

ecological succession that begins on area that has never been

occupied by a community of organisms


Secondary Succession

-

ecological succession that begins on area that had be
en occupied

by a community of organisms


Biotic Potential

-

capacity of a species for reproducing itself (due to reproductive rate,

defense mechanisms, migration, etc.)


Environmental Resistance

-

combination of all factors that limit the survival of a s
pecies’

members (lack of food, water, habitat, predators, disease, etc.)


An example of the above is the
predator
-
prey relationship


Ecosystems have
Stability

-

ability of a living system to withstand or recover from

externally imposed changes or stresse
s



a)
inertia stability (persistence)

-

ability of a living system to resist being disturbed


or altered



b)
resilience stability

-

ability of a living system to restore its structure & function


to an original condition following a natural or
human
-
induced stress, provided the

outside disturbance is not too drastic

Species Diversity

-

number of different species & their abundance in a given area; it affects


the inertia stability. high species diversity tends to increase long
-
term persistence
.

It

has more ways of responding to most environmental stresses.

(Exceptions: coastal salt marshes with low species diversity have high persistence;


rocky intertidal seashores with high species diversity have low persistence)


Range of Toleran
ce

-

range or span of conditions that must be maintained for an organism

to stay alive & grow, develop & function normally


Limiting Factor Principle or Law of Tolerance


-

the existence growth, abundance or distribution of an organism can be determined b
y
whether the levels of one or more limiting factors go above or below the levels required by the
organism


In response to changing conditions or stress, organisms can:

1) migrate (move)

2) undergo readaptation (change)

3) become extinct (die)


Threshold E
ffect

-

phenomenon in which no effect is observed until a certain level or

concentration is attained


Speciation

-

splitting of a single species into two different species. It normally occurs when

a species’ population is distributed over many environmen
ts. It is a slow process &

normally requires 1000 generations


Biological Magnification

-

buildup in concentration of a substance in successively higher

trophic levels of the food chain or web


In dealing with ecosystems, we must remember:

1) interdepen
dence

2) diversity

3) resilience

4) adaptability

5) limits