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Biogeochemical
Cycles
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Bio means…
– life
Geo means…
– Of earth: parts of earth are
• Land, air, water
Chemical means…
– Molecules and/or compounds
Cycle means…
– Repeatedly
• Cycling of materials between the environment and
organisms
• Chemical and biological processes
• Examples
– Water cycle
– Nitrogen cycle
– Phosphorus cycle
– Carbon cycle
Plants obtain nitrogen
from nitrogen-fixing
bacteria and pass it to
other organisms through
the food chain
Cycles of Matter
• No definite beginning or end like food chain
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(remember, energy flow is
unidirectional)…matter is recycled
Does not use up matter…transforms it
Biogeochemical process
– Pass same molecule/compound/element through
biosphere over and over
• Organism to organism
• First Part of biosphere (air, land, water)
• Second Part of biosphere (air, land, water)
Biogeomchemical cycles
• Carbon-oxygen
• Phosphorus
• Water
• Nitrogen
• Water Cycle
• Evaporation: water (in oceans, rivers, lakes) turns to water vapor and
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rises
Transpiration: water evaporates through the stomata of a plant’s leaves
and becomes water vapor
– Adhesion and cohesion enable water molecules to move from roots to
leaves
– Stomata: tiny openings in the leaves of plants
Condensation: water vapor cools down and condenses in atmosphere to
make CLOUDS
Precipitation: water returns to surface as rain, snow, ice
Run-off: water that moves from mountains and hills to rivers and stream
and then eventually to ocean
Seepage: water that seeps into the soil and is either taken up by plant
roots or becomes part of ground water
Ground water: Water that exists beneath the earth's surface in
underground streams and aquifers that eventually becomes part of the
ocean
Water Cycle
Water Cycle Impact
• Deforestation
– Freshwater returns to atmosphere by
TRANSPIRATION from tropical forests
– Cut down tropical forest=reduce water vapor in
air=changes in precipitation patterns and effects
ecosystems
• Irrigation and household water use
– Draws water up from aquifers and rivers
– If rate at which H2O is used is FASTER than the
water cycle can replace it, rivers and aquifers may
run dry (effects ecosystems)
Carbon-oxygen cycle
• Carbon is the main component of all living
things
• Carbon is found in glucose, which is the
fuel for LIFE!
• What other things do we fnd carbon in?
Carbon cycle
Carbon
released as:
Carbon is taken
in by
• Carbon dioxide
– Animals and humans release
CO2 by cellular respiration
– Volcanic eruptions
– Burning of fossil fuels (oils)
• Methane (CH4)
– Grasses and animals release
• Bicarbonate ions
– Found in rock and released
during erosion
• Plants
• When light is
present, plants use
photosynthesis to
make CO2 and
H2O into glucose
and oxygen
Carbon Cycle
Carbon cycle impacts
• Atmospheric CO2 levels have steadily risen (more
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industrialized)
Burning of wood and fossil fuels release CO2 into atm
Deforestation affects carbon cycle
– Def: clearing of forests for lumber, agriculture, etc.
– Eliminates plants that absorb excess CO2 from the air
– “Slash and burn” removes plants and adds CO2 to air
• Greenhouse effect
– When atmospheric gases trap heat close to Earth’s surface
– Makes Earth “liveable”…not a bad thing as long as it is controlled
• Global warming (theory)
– Theory that there is an overall rise in global temperatures b/c of
increase in greenhouse gasses (CO2)
– NOT proven
Nitrogen cycle
• Where is nitrogen found in living things?
• Proteins, nucleic acids, and more!
• Do you think nitrogen is important?
Nitrogen cycleAtmospheric nitrogen (N2) makes up nearly
78% of atmosphere
Organisms can not use it in that form.
Lightning and bacteria convert nitrogen into
usable forms.
Terms to know…
• Fixation
– When N2 gas is made into a useable form (NH4) ammonia
• Nitrification
– Conversion of ammonia (NH4) into nitrates (NO3-) and
nitrites (NO2-)
• Assimilation
– when plants take up nitrates and nitrites and incorporate
into their tissue as amino acids which become proteins
• Ammonification/Mineralization
– When plants and animals die and decomposers convert
amino acids back into ammonia (NH4) and return to soil
Nitrogen cycle: Forms of Nitrogen
• Nitrogen gas N2
– Nitrogen in atmosphere and nitrogen in decaying organisms
needs to be converted
– Nitrogen-fixation by bacteria on roots of legumes;
Nitrogen GAS  Ammonia (sometimes nitrates)
• Ammonium (NH4+ )Ammonia NH3
– Nitrification by bacteria in soil; AMMONIA  Nitrates
and nitrites
• Nitrates NO3- and Nitrites NO2-
– When oxygen is low in terrestrial and marine environments
bacteria convert Nitrogen compounds back into Nitrogen gas
N2
• Denitrification when nitrogen containing compounds
(Ammonia and nitrates/ites)  nitrogen gas by
denitrifying bacteria in soil
Nitrogen Cycle
Nitrogen Cycle Impacts
• Humans move large amounts of nitrogen into air or water
– Sewage treatments, fertilizers
• Lots of Nitrogen in water (and phosphorus) enables algae to
grow rapidly on the surface…eutrophication
– Definition: excess nutrients in water causes increase in algae (plant)
growth which leads to increase in bacterial growth
– As algae dies, bacteria that consumes them use up so much available
oxygen in the water that there isn't enough for the other marine
organisms
• Lots of Nitrogen (and sulfur) in Air
– Smokestacks and car exhaust pipes release nitrogen dioxide
– NO2 reacts with oxygen to make O3 (ozone) in low levels of the
atmosphere….this is very bad for living organisms
– These nitrogen and sulfur containing compounds mix with water in the
air to make NITRIC ACID and SULFURIC ACID
– These acids evaporate, condense and come down as ACID
PRECIAPTATION (acid rain)
– Acid Rain causes damage to soils and aquatic ecosystems
Do NOT copy word-for-word!!!
-Fertilizers used in farming cause run-off
into nearby water=increase in nutrient
levels=phytoplankton to grow and
reproduce rapidly=algal blooms
-This bloom of algae disrupts normal
ecosystem & increases bacteria…bacteria
use up all the oxygen in the water and
there is none left for other marine
life…this causes death of many aquatic
organisms that need the oxygen
-Blooms also block sunlight penetrating
the surface and photosynthetic marine
plants can’t get sunlight
-Blooms also produce toxins that are
harmful to higher forms of life
-Cause problems along the food chain and
affect any animal that feeds on them.
Phosphorus cycle
• Where do we find phosphorus?
• Part of DNA, cell membranes, ATP and
ADP, activates and inactivates enzymes
• Do you think phosphorus is important?
Phosphorus Cycle
• NO phosphorus in the atmosphere
– Only cycles in soil and land
• Found as Phosphorus (P) or Phosphate
(PO4-)
• Primarily found in the form of mineral
apatite
– found in rocks and phosphorus minerals
Four Phase of Phosphorus Cycle
(Terrestrial)
• Weathering
– Weathering away of phosphate rocks leached phosphate into
soil
• Plant Uptake
– Plants take up P from soil and incorporate into tissues and
the animals eat the plants and ASSIMILATE phosphorus
into their tissue
• Decomposer release
– Plants and animals die, decomposer break down tissue and
release phosphorus back into soil
• Animal exrements
– Containphosphorus and return to soil
Four Phase of Phosphorus Cycle
(Aquatic)
• Weathering
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– Weathering away of phosphate rocks and soils leach phosphate into rivers and
streams
Aquatic plant and Phytoplankton Uptake
– Take up P in water and incorporate into tissues and the marine vertebrates and
invertebrates eat the plants/plankton and ASSIMILATE phosphorus into their
tissue
Decomposer release
– Aquatic plants and animals die, decomposer break down organic phosphate in
tissue and release inorganic phosphate back into water
Animal excrement
– Contain phosphorus and return to water
Phosphate Loss
– Phosphate lost to marine sediment which is eventually converted into
pphosphate0containing rock by geological processes
Pollution and the Environment
• Pollution: addition of substances to the
environment that result in a NEGATIVE effect
• Biological Magnification
– Animals take in water and nutrients and sometimes
pollutants w/them
– While energy decreases as it moves up the food chain,
toxins increase in potency.
– PCBs
• Disposed in industrial wastes and Soluble in lipids of
dichlor-diphenyltrichlorethylene
C14H9Cl5
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animals
Concentration of PCBs increases in organisms tissues
increase as you move up trophic levels
– DDTs
• Chemical used to control mosquitoes and crop pests
• Soluble in fatty tissue
• Birds had high levels of DDT in their tissue and in egg
shells, which causes shells to be brittle and young birds
cannot survive
Damage to Ozone
• Ozone: gas in atmosphere (O3)
• Ozone absorbs UV radiation from the sun (protects organisms on
earth from harmful rays)
• Chlorofluorocarbons (CFCs) is a chemical released from aerosol
cans, refrigerator units and certain manufacturing processes
– Chlorine from CFCs pull off an oxygen from a molecule of O3,
making chlorine monoxide, ClO and ozone into regular O2
– ClO binds with another ClO making chlorine peroxide (Cl2 O2)
– There’s one less molecule of O3 in the atmosphere to protect
organisms from harmful UV radiation
– Sun also breaks the chlorine peroxide (Cl2 O2) into chlorine
atoms and another O2 molecule and the cycle continues with
more carbons interacting with ozone molecules
– “Holes in the Ozone”
Biodiversity
• Definition: # of species in an ecosystem;
the variety of ecosystems; the variety of
individuals in a species
• Why is biodiversity important?
– Species in ecosystem are interconnected and
depend on each other
– If one species disappears, many others
affected
– Humans depend on biodiversity as well (food,
shelter, clothing, medicine)
Threats to Biodiversity
• Habitat destruction
– Pollution, deforestation, desertification,
urbanization
• Introduced Species
• Over Exploitation of resources
Conservation Biology
• Def: application of biology to counteract the threats to biodiversity
– Focus on hot spots
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Small geographic areas with high conc. of species
Cover less than 1.5% of earth’s surface
Hotspots of extinction
Contain 1/3 of all plants and vertebrates
– Understand Organism’s habitats
• Helps maintain org. habitat or create new habitats
• Biologists can protect key habitat factors of species
– Balance demand for resources
• Save species or meet economic and social needs of people
• Save a forest to protect and owl but put many loggers out of work?
– Planning for a Sustainable future
• Ways nations protect environment for future:
• Zoned reserves-areas of land that are relatively undisturbed by humans
– Encourage long term ecosystem conservations
• Buffer zones-areas that surround “zoned” reserve; these buffers are minimally
impacted by people...no major envir. disturbances
– Ex. Costa Rica- 8 zoned reserves
• Sustainable development- developing ways to use natural resources so that the
can they are not depleted for future generations
– renew themselves and be available to the future…
– Ex. Forest corridor between farmlands
SUSTAINABILITY!!!
• Strategy for using natural resources
without depleting them
• Using natural resources to provide for
human needs without causing long-term
environmental harm
• Ex. Water restrictions
• Ex. Going green