Transcript WATER CYCLE = The process by which water is circulated

Biogeochemical
Cycles
WATER CYCLE
• Also called the
Hydrologic Cycle
• Water is
circulated through
the global
ecosystem.
• Fresh water
evaporates and
condenses back
to earth.
OVERVIEW
Water evaporates into the
atmosphere, condenses, and
falls to earth as rain, snow, or
sleet. The water then flows
to the oceans to begin the
cycle again. Energy to keep
the cycle moving comes from
the sun.
KEY PROCESSES OF
THE WATER CYCLE
Evaporation
Transpiration
Condensation
 Precipitation
EVAPORATION
*Occurs when solar
energy causes water from oceans,
fresh water bodies, land, and
plants to move from the earth to
the atmosphere
* All impurities dissolved in water
are left behind; water vapor is pure
water
Transpiration
•The
evaporation
of water
from leaves
CONDENSATION
* The process by which a gas
becomes a liquid
* Clouds form from the
condensation of water vapor
PRECIPITATION
* The process by which
water falls from clouds
as rain, snow, sleet, and
hail.
OTHER STUFF ABOUT
WATER
* Water flows over the land as runoff
or soaks deep into the soil and rock
underground becoming groundwater.
* An aquifer is an underground
reservoir of fresh water trapped
by rocks.
Planet earth’s water system is a closed system.
Water molecules are used over and over again.
No new water molecules leave or enter the water
system.
BIG IDEA:
The water we drink
connects us with living
organisms from our
distant past.
This same water will
be used by organisms
in the future.
Critical Thinking
“Water, water everywhere, but not a
drop to drink!”
Water covers 75% of planet earth.
The water cycle is a closed system
that returns water repeatedly to our
planet. So, water is a renewable
resource. If this is true, why is it
important to conserve water?
The Carbon Cycle
• Basic constituent of all organic
compounds (Life !)
• 760 billion tons in the atmosphere.
• 0.035% of the atmospheric elements.
Forms of Carbon
• Atmosphere = CO2
• Living and decaying matter
= proteins and carbohydrates
• Oceans = salts
• Rocks = carbonate solids
• Fossil fuels =
Petroleum, hydrocarbons, and coal
Atmospheric Carbon
Sources
Carbon enters the atmosphere in
many ways:
• Cellular Respiration
• The decay of plant and animal
matter
• The evaporation of the ocean
waters
• Volcanic activity
• The burning of fossil fuels
Terrestrial Carbon
• Assimilation through
photosynthesis by
autotrophs
• Ocean reservoirs (“sink”)
• The weathering of rocks
• Organic matter which
becomes fossil fuels.
CARBON CYCLE
Carbon Cycle
The Carbon Balance
• The net result of all of these
interactions in that the
amount of carbon in the
atmosphere remains
constant even though
carbon atoms constantly
leave and enter the
atmosphere as they cycle.
Upsetting the Balance
• Burning of fossil fuels (6 billion
tons per year)
• Deforestation (1 billion tons per
year)
The concentration of carbon in
our atmosphere has increased
25% in the last century alone!
Critical Thinking
The increase in carbon dioxide in the atmosphere
has precipitated what scientists now call “The
Greenhouse Effect”. The CO2 molecules trap the
suns energy and heat as it is reflected from the
planet back towards the atmosphere. As global
temperatures continue to rise, the concern is not
with the fact that we have a greenhouse effect, but
whether human activities are leading to an
enhancement of the greenhouse effect by the
emission of greenhouse gases through fossil fuel
combustion and deforestation. Create a graph to
show how human activities could make the
temperature on our planet rise regardless of natural
temperature cycles over long periods of time on the
planet. (Hint: Think slope of the temperature line.)
NITROGEN CYCLE
• Overview
– Needed by organisms to
make proteins
– Makes up 80% of our
atmosphere
– Nitrogen (N2 ) can not be
used by organisms and
must be “fixed”
NITROGEN CYCLE
STEPS OF THE
NITROGEN CYCLE
•Nitrogen Fixation
•Nitrogen Reservoirs
•Nitrogen Release
NITROGEN FIXATION
Nitrogen-fixing bacteria
are found in soil, water,
and the roots of some
plants.
Nitrogen fixation:
process by which
bacteria converts
gaseous nitrogen (N2) into
ammonia (NH3).
NITRIFICATION
bacteria take
ammonia (NH3)
and convert it
into nitrites
(NO2 ) and
nitrates (NO3 )
NITROGEN RESERVOIRS
Plants take in
nitrates from the
soil.
Animals can
obtain nitrogen
by eating plants.
NITROGEN RELEASE
Returned to the soil by:
•Animal waste
•Decomposition of
organisms
•Ammonification=
the decomposition of
organic nitrogen to
ammonia
NITROGEN RELEASE
Returned to the atmosphere by:
Denitrification: process
by which bacteria convert
nitrate (NO3 ) back to
gaseous nitrogen (N2).
Critical Thinking
Farmers add fertilizer to their crops
to increase their yield. Extra
fertilizer often is carried in
irrigation waters to rivers, streams,
ponds, and lakes nearby. What are
some of the possible outcomes for
a lake ecosystem that receives the
fertilizer runoff?