Transcript Biochemical Cycles

Biogeochemical cycles
Water, Carbon, Nitrogen
THE WATER CYCLE (hydrologic)
• Water moves between the ocean
atmosphere, and land. Water molecules
enter the atmosphere as water vapor, a
gas that forms from bodies of water.
• The process of water changing from liquid
to atmospheric gas is called evaporation.
Evaporation is the stage
where water travels from
the Earth’s surface to the
atmosphere.
Water molecules are
heated up by the sun,
and water is changed
from a liquid form to a
gas form.
Evaporation can be seen in
your life every day. Have you
ever watched a kettle boil? The
steam you see going in to the
air is an example of
evaporation!
• It can also enter the atmosphere from the
leaves of plants in a process called
transpiration.
• As warm moist air rises, it starts to cool.
Eventually, the water vapor forms tiny
droplets that form clouds. This is known
as condensation.
• DROP SIZE AND CLOUD APPEARANCE The
smaller the drops in a cloud the brighter the tops
appear (and the darker the bases). Smaller droplets
scatter more sunlight, while large drops allow more
sunlight to pass through.
• This explains why the heavily raining part of a
shower cloud or thunderstorm is usually brighter
than just the cloudy part. The cloud droplets have
combined into large raindrops, which allow more
sunlight to pass through them.
• When the droplets become large enough,
the water returns to the Earth’s surface in
the form of precipitation–rain, snow,
sleet, or hail.
• On land, much of the precipitation runs
along the surface of the ground until it
enters a river or stream that carries the
runoff back to an ocean or lake.
• Rain seeps into the soil, some of it deeply
enough to become ground water. Water
in the soil enters plants through roots, and
the water cycle begins again.
THE WATER CYCLE:
What about the Carbon Cycle?
Carbon is continually
recycled between
inorganic and organic
forms.
THE CARBON CYCLE:
Inorganic carbon exists as a gas in the
atmosphere, and is dissolved in the ocean
water.
Fixing
Carbon, nitrogen and phosphorus is
fixed when these elements are joined to
atoms of other elements.
This makes them useful for living
organisms, which can use the fixed
elements in organic compounds.
• During the carbon cycle, inorganic carbon
in the form of carbon dioxide (CO2) is
converted to an organic form through
photosynthesis. This is called fixing
carbon. Plants and algae can fix carbon
through photosynthesis.
• Organic carbon is changed to inorganic
carbon once again through metabolism
(cellular respiration).
• Fossil fuels are a form of stored organic
carbon. When fossil fuels are burned
through combustion (through human
activities), CO2 is produced, which may then
reenter the atmosphere.
• CO2 is a greenhouse gas. An increase in
greenhouse gases is causing global
warming.
The Carbon Cycle
The Nitrogen Cycle
Nitrogen is continually recycled between inorganic and organic forms.
• All organisms require nitrogen to make
proteins.
• Nitrogen exists in the atmosphere as
inorganic N2.
• Inorganic nitrogen can be converted to an
organic form that can be used by
plants
& algae.
• N2 can be fixed by lightning.
• and soil bacteria (such as those in
root nodules of plants).
• This is called fixing nitrogen,
as atmospheric nitrogen is
chemically joined or fixed to
other atoms.
• [Inorganic nitrogen is converted to organic
forms such as: ammonia (NH3), nitrate
ions (NO3-),and nitrite ions (NO2-) through
the action of bacteria.
• Farming adds organic nitrogen in the soil in
the form of fertilizer.
• Decomposers return nitrogen to the soil (in
the form of ammonia), bacteria
• while other bacteria convert it to back to
nitrogen gas (N2) in a process called
Denitrification.
• Nitrogen is continually recycled
between inorganic and organic forms.