BIOGEOCHEMICAL CYCLES:
 The RECYCLING of MATERIALS through living
organisms and the physical environment.
BIOCHEMIST:
Scientists who study how LIFE WORKS at
a CHEMICAL level.
The work of biochemists has led to the
understanding that LIVING ORGANISMS are
composed of some of the SAME elements
that are found in air, water, and soil.
Although there are 92 elements known to
occur naturally on Earth, fewer than 20
elements are presently known to occur in the
tissues of living things.
For example, only 6 elements make up 99.2
% of human tissue . . . And pumpkin tissue!!!
Look at the table on the following slide to
see a comparison between the elements in
the EARTH’s CRUST, a HUMAN, and a
PUMPKIN!
CONCLUSIONS:
So . . . .you don’t really need to dress up like
a pumpkin!!!
•And when you say you feel like dirt, you kind
of are like dirt!

Oh yeah, and also . . .
THE FOUR ELEMENTS that make up the
MAJORITY of LIVING TISSUES are:
•OXYGEN
•CARBON
•HYDROGEN
•NITROGEN
THE CYCLING PROCESS
The 4 elements --O, C, N, and H –are cycled
constantly between 2 parts of nature:
 LIVING ORGANISMS
 PHYSICAL ENVIRONMENT
The cycling of these elements is
dependent on two types of processes in
order to work:
•BIOLOGICAL PROCESSES
•GEOLOGICAL PROCESSES
BIOLOGICAL PROCESSES
The cycling of these elements requires
LIVING ORGANISMS, which make up the
BIOSPHERE of Earth.
What are some examples of BIOLOGICAL
PROCESSES?
•Respiration
•Photosynthesis
•Decomposition
•Assimilation
•Excretion
GEOLOGICAL PROCESSES
The cycling of these elements require the
PHYSICAL ENVIRONMENT, which INCLUDES:
 AIR –ATMOSPHERE
 LAND –GEOSPHERE
 WATER -HYDROSPHERE
What are some examples of GEOLOGICAL
PROCESSES? •FOSSILIZATION
•EROSION
•COMBUSTION/BURNING
•WEATHERING
•SEDIMENTATION
3 TYPES OF CYCLES
CARBON
CYCLE
NITROGEN CYCLE
OXYGEN CYCLE
THE CARBON CYCLE P. 62-65
DEFINITION: The cycling of carbon through the
atmosphere, the physical environment, and
ecosystems.
CARBON AND THE BIOSPHERE
HOW IMPORTANT IS CARBON for LIFE?
 Carbon is the ELEMENT that is the
BACKBONE for ALL LIFE on Earth. In other
words, we are CARBON-BASED life forms.
HOW DOES CARBON MOVE THROUGH LIVING
ORGANISMS?
The two main PROCESSES that help
cycle CARBON through the BIOSPHERE
are:
•PHOTOSYNTHESIS
•CELLULAR RESPIRATION
WHERE IS CARBON STORED IN THE NON
LIVING PHYSICAL ENVIRONMENT?
2 TYPES OF CARBON STORAGE:
1) Organic Reservoirs: Carbon that has been
stored as the result of decomposition of
living organisms. PEAT, COAL, OIL and
NATURAL GAS
2) INORGANIC RESERVOIRS:
•AIR –0.03 % of air is carbon
•OCEANS –both dissolved (CO2 gas) and in
shells (CaCO3 –calcium carbonate)
•LAND –in sedimentary rocks, which can be
released during volcanic eruptions
NITROGEN CYCLE P. 66-67
DEFINITION: The movement of nitrogen
through the atmosphere, physical
environment and ecosystems.
SIMPLIFIED NITROGEN CYCLE
WHAT IS NITROGEN USED FOR IN LIVING
ORGANISMS?
Nitrogen is used to make DNA and PROTEINS.
DNA is the GENETIC MATERIAL found in every
living cell.
Most nitrogen on Earth is found in the air.
•The air is 79% NITROGEN.
•This atmospheric nitrogen is in the form N2, a
gas.
Although nitrogen is plentiful in the air, it is
UNUSABLE to most living organisms (we cannot
simply “breathe in” nitrogen).
HOW DO LIVING ORGANISMS GET NITROGEN?
Plants and animals cannot use N2 gas.
We can use nitrogen in TWO FORMS:
•AMMONIA, NH3
•NITRATES, NO3WHAT ARE THE KEY NITROGEN CYCLE PROCESSES?
NITROGEN FIXATION
DENITRIFICATION
NITROGEN FIXATION
Also known as NITRIFICATION
Gaseous nitrogen, N2, is converted to
usable forms in TWO WAYS:
•By LIGHTNING
•By NITROGEN-FIXINGBACTERIA
These bacteria are found in the
ROOT NODULES of LEGUMES
such as ALFALFA and CLOVER.
DENITRIFICATION
DENITRIFYING BACTERIA convert usable forms
of nitrogen back into gaseous nitrogen, N2.
These bacteria are found in the soil.
HUMAN IMPACTS ON THE......
CARBON CYCLE
GLOBAL WARMING and the GREENHOUSE
EFFECT
NITROGEN CYCLE
AQUATIC EUTROPHICATION
GLOBAL WARMING AND THE GREENHOUSE
EFFECT
Humans have DISRUPTED the CARBON CYCLE
in TWO MAIN WAYS:
Burning FOSSIL FUELS –
Increased CO2
DEFORESTATION –
Decreased O2 production by plants
Increased CO2
These INCREASES in CO2 Levels
have led to an ENHANCED
GREENHOUSE EFFECT.
WHAT ARE GREENHOUSE GASES?
Gases that have the ability to HOLD HEAT IN
the atmosphere.
These gases are important to keep the Earth
warm enough to sustain life.
3 MAIN GREENHOUSE GASES
1) CARBON DIOXIDE CO2
Sources:
•Cellular Respiration
•Combustion (burning)
2) METHANE CH4
Sources:
•Fossil fuel production and transportation
•Decomposition
•Livestock
3) NITROUS OXIDES NOx
Sources:
•Combustion
•Agricultural Fertilizers
•Industrial Emissions
GLOBAL WARMING 101
Humans have DRAMATICALLY INCREASED the
amount of greenhouse gases in the
atmosphere, leading to the ENHANCED
GREENHOUSE EFFECT, or GLOBAL WARMING.
POSSIBLE EFFECTS
Increased spread of disease
 Rising sea levels and loss of polar ice caps

Figure below is 1979 versus 2005
Loss of freshwater sources
 More extreme weather
 Accelerated species extinction

AQUATIC EUTROPICATION
Humans have impacted the nitrogen cycle by
releasing 2 substances into AQUATIC
ECOSYSTEMS:
•FERTILIZERS
•UNTREATED HUMAN SEWAGE
Fertilizers, and untreated human sewage,
contain NITRATES and PHOSPHATES.
These chemicals LEACH into water ways
through groundwater, road runoff, etc.
Lakes that have HIGH LEVELS of phosphates
and nitrates can undergo EUTROPHICATION
A transformation from an OLIGOTROPHIC LAKE
to a EUTROPHIC LAKE.
THINK ABOUT IT!!!!!!!!!!!!!