Second Law of Thermodynamics (Law of Energy Degradation)


Oct 27, 2013 (4 years and 6 months ago)


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


(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
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

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

Food Web


complex, interlocking series of food chains


hydrologic (water

hydrogen & oxygen).

gaseous (carbon, oxygen, nitrogen),

sedimentary (phosphorus, sulfu
r, etc.)



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

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



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



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.



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

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

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
(location where an organism lives &


habitat & niche are analogous to address & occupation/life

Competitive Exclusion Principle


no 2 species in the same ecosystem can occupy exactly

the same ecological niche indefinitely

The number of “niche
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

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

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

An example of the above is the
prey relationship

Ecosystems have


ability of a living system to withstand or recover from

externally imposed changes or stresse

inertia stability (persistence)


ability of a living system to resist being disturbed

or altered

resilience stability


ability of a living system to restore its structure & function

to an original condition following a natural or
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


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


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
whether the levels of one or more limiting factors go above or below the levels required by the

In response to changing conditions or stress, organisms can:

1) migrate (move)

2) undergo readaptation (change)

3) become extinct (die)

Threshold E


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

concentration is attained



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

2) diversity

3) resilience

4) adaptability

5) limits