2 ecosystem
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8/6/2019 2 Ecosystem
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Environmental
Chemistry
Is the study of the sources,
reactions, transport, effects andfates of chemical species in the
water, soil, air and organism in
the environment
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What is environmental chemistry?
"What is environmental chemistry? This question is a littledifficult to answer because environmental Chemistryencompasses many different topics. It may involve a study
of Freon reactions in the stratosphere or an analysis of toxic deposits in ocean sediments. It also covers thechemistry and biochemistry of volatile and solubleorganometallic compounds biosynthesized by anaerobic
bacteria. Environmental chemistry is the study of
the sources, reactions, transport, effects, andfates of chemical species in water, soil, and airenvironments."
- Stanley E. Manahan. 1991. Environmental Chemistry,Fifth edition.
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What does an environmental chemist do?
Environmental
Chemist
Prevent
Environmental
deterioration
Environmental
Clean-up
Environmental
Research Environmental
Regulation
Environmental
Measurement
& Monitoring
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Ecology
A study of interactions of organisms with
each other and with physical environment(both biotic and abiotic).
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Examples of interactions
competitions among plants for light
tree and animal disperser
growth of a crop and soil fertility
forests as a sink for atmospheric carbon
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Ecosystem:
³a spatially explicit unit of the Earththat includes all of the organisms,
along with all the components of the
abiotic environment within its
boundaries.´
Gene Likens
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Ecosystem
the environment within which
interactions take place, subject to
influences both internal and external,with inputs and outputs OF ABIOTIC
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Study of ecosystem includes living community
plus physical environment.
a. Living (biotic) components : habitats and
niches.b. Nonliving (abiotic) components: soil, water,
light, inorganic nutrients, and weather
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Habitat = organism's place of residence,
where it can be found, such as under a log.
Niche = profession or role of that organism
in the community, factors limiting its life,
and how it acquires food
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Producers = autotrophic photosynthetic
organisms.a. In terrestrial ecosystems, producers are
predominantly green plants.
b. In freshwater and marine ecosystems,dominant producers are algae.
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C onsumers are heterotrophic organisms
that eat preformed food.a. Herbivores feed directly on green plants;
are primary consumers.
b. Carnivores feed on other animals and are
secondary or tertiary consumers.
c. Omnivores feed on both plants and
animals; for example, humans eat both
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d. Decomposers are organisms of decay.i. Mostly are bacteria and fungi.
ii. Break down detritus, nonliving
organic matter, into inorganic matter.
iii. Small soil organisms are critical in
helping bacteria and fungi shred leaf
litter and form rich soil.
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Energy Flow and Chemical Cycling
Energy flow in ecosystems based on two
laws of thermodynamics:
(a) First law states energy cannot becreated or destroyed.
(b) Second law asserts that when energy is
transformed from one form to another, someusable energy is lost as heat.
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The Food Chain
Figure : A Pond Ecosystem. Each of the roles of producer, consumer, and
decomposer is filled by a number of different organisms in a pond
ecosystem.
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A Food Pyramid in the Temperate Rain Forest Biome
Segments of Pyramid Show Relative Biomass at Each Trophic Level
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marine environmentmarine environment::
open ocean ± low primary productivity, often limiting N, P, Fe resulting in
low heterotrophic activity
inshore ± nutrient rich resulting in greater productivity
deep sea habitatsdeep sea habitats::
about 75% of ocean water is at depths of greater than 1000 m
mostly dark, cold (2-3ºC), high hydrostatic pressure, very low nutrient
input (marine snow)low microbial activity; inhabitants are psychrotolerant or psychrophilic,
barotolerant or barophilic
sort of a cold, wet desert
..... and then we have hydrothermal vents, analogous to oases in
deserts
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hydrothermal venthydrothermal vent
communitiescommunities:
driven by geothermal energy
microbe-animal symbioses
�free-living microorganisms
include S-oxidizing
chemolithotrophs (Thiot hrix,Beggi atoa, Thiobacillus), may
also be H2-, Fe2+-, Mn2+-
oxidizers, methanotrophs,
nitrifiers
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tube worms: can be 2 m+ long
� lack mouth, gut, anus
� possess trophosome, spongy tissue packed with S granules and S-oxidizing
bacteria� bacteria grow on H2S, thiosulfate and CO2
� tube worm traps O2, H2S in blood and delivers to bacteria
� dead bacteria, products of bacterial metabolism support tube worm
S A9a
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³black smoker´
³snowblower´: tufts of bacterial biomass blown out
of a vent into overlying water
S A9bbacteria (green) & archaea (red) from
black smoker chimney material
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the habitats we¶re used to: the hydrothermal vent habitat:
plant
(phototrophic
& autotrophic)
lightlight CO2
carbonenergy
animal
(organotrophic &heterotrophic)
carbon
& energy
cow
S-oxidizing bacterium
(chemolithotrophic &
autotrophic)
tube worm
(organotrophic &heterotrophic)
HH22SS CO2
energy carbon
carbon& energy
� driven by sunlight � driven by geothermal energy
S A9d
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Food Chains Become Food Webs
Food chain = simply "who eats what".
Food web = weaves together many food
chains to form a complicated networkof feeding relationships.
Many animals eat more than one thing, and
each link in each chain is important andintegral to the entire system.
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Populations Form a Pyramid
Trophic structure of an ecosystem forms anecological pyramid.
Base of pyramid represents producer trophiclevel, apex is highest level consumer or the top
predator. Pyramid of numbers is based on number of
organisms at each trophic level.
Pyramid of biomass is calculated by multiplyingthe average weight for organisms times thenumber of organisms at each trophic level.
Pyramid of energy calculates amounts of energyavailable at each successive trophic level.
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The food energy pyramid always shows a
decrease moving up trophic levels because: i. Only a certain amount of food is captured and
eaten by organisms on the next trophic level.
ii. Some of food that is eaten cannot be digested and
exits digestive tract as undigested waste. iii. Only a portion of digested food becomes part of
the organism's body; rest is used as source of energy.
iv. Substantial portion of food energy goes to build up
temporary ATP in mitochondria; ATP energy is thenused to synthesize proteins, lipids, carbohydrates,and fuel contraction of muscles, nerve conduction,etc.
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Only about 10% of energy available at a
particular trophic level is incorporated into
tissues at the next level. Example: a larger
population can be sustained by eating grain
than by eating grain-fed animals since 100kg of grain would result in 10 human kgs but
if fed to cattle, the result is 1 human kg.
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Although sometimes usedinterchangeably with 'bioaccumulation,'an important distinction is drawnbetween the two.
Bioaccumulation occurs w it hin a
trophic level, and is the increase inconcentration of a substance in anindividuals' tissues due to uptake fromfood and sediments in an aquatic milieu.
Bioconcentration is defined asoccurring when uptake from the water isgreater than excretion.
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Barry Commoner
One of Commoner's lasting legacies is his four laws of ecology,as written in The C losing C ircle in 1971. The four laws are:
1. Everything is Connected to Everything Else.
There is one ecosphere for all living organisms and whataffects one, affects all.
2. Everything Must Go Somewhere. There is no "waste" in nature and there is no ³away´ to which
things can be thrown.
3. Nature Knows Best.
Humankind has fashioned technology to improve upon nature,but such change in a natural system is, says Commoner, ³likelyto be detrimental to that system.´
4. There Is No Such Thing as a Free Lunch.
In nature, both sides of the equation must balance, for everygain there is a cost, and all debts are eventually paid.
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