Transcript Document

Nutrient Cycling Through the
Ecosystem
NUTRIENT CYCLES: ECOSYSTEM TO
ECOSPHERE
• Nutrient cycling occurs at the
local level through the action
of local organisms.
• Nutrient cycling occurs at the
global level through
geological processes:
– atmospheric circulation
– erosion
– weathering.
The Law of Conservation
• The Law of Conservation of mass, matter and
energy states that none of these can be
created or destroyed.
• That’s all we have and there ain’t no more!
NUTRIENT CYCLES
• Nutrient cycles allow the Law of Conservation of
Mass, Matter and Energy to work.
• The atoms of earth and life are the same; they just
find themselves in different places at different times.
• Most of the calcium in your bones came from cows,
who got it from corn, which took it from rocks that
were once formed in the sea.
• The path atoms take from the living (biotic) to the
non-living (abiotic) world and back again is called a
biogeochemical cycle.
A GENERALIZED MODEL OF NUTRIENT
CYCLING IN AN ECOSYSTEM
• The cycling of nutrients in an
ecosystem are interlinked by
processes that move atoms
through compartments
–
–
–
–
organisms
Atmosphere
soil and/or rocks
water.
• Nutrients can flow between
these compartments along a
variety of pathways.
The Cycles we will learn
•
•
•
•
•
Water- next unit
Carbon- NOW
Nitrogen- NOW
Phosphorus- NOW
Sulfur- next year in AP Environmental
The Carbon Cycle
1. Every organic molecule contains
the element carbon.
A. Carbon and oxygen form carbon
dioxide gas (CO2), an important
component of the atmosphere.
B. Carbon dioxide is taken in by
plants during photosynthesis and is
given off by plants and animals
during cellular respiration.
The Carbon Cycle
2. Four main types of processes move carbon through its cycle:
A. Biological processes, such as photosynthesis, cellular respiration,
and decomposition, take up and release carbon and oxygen.
B. Geochemical processes, such as erosion and volcanic activity,
release carbon dioxide into the atmosphere and oceans.
C. Mixed biogeochemical processes, such as the burial and
decomposition of dead organisms and their conversion under
pressure into coal and petroleum (fossil fuels), store carbon
underground.
D. Human activities, such as mining, cutting and burning forests, and
burning fossil fuels, release carbon dioxide into the atmosphere.
Burning of
Fossil Fuels
CO2 in Atmosphere
Cellular Respiration
Photosynthesis
Coal and Petroleum
Decomposition of
dead organisms
The Nitrogen Cycle
1. All organisms require nitrogen to make amino acids, which in turn
are used to build proteins.
A. Nitrogen gas makes up 78% of Earth’s atmosphere.
B. Nitrogen containing substances such as ammonia (NH3), nitrites
(NO2-), and nitrates (NO3-) are found in the wastes produced by
many organisms and in dead and decaying organic matter.
C. Nitrate is major component of plant fertilizers.
The Nitrogen Cycle
2. Nitrogen gas is the most abundant form but only certain bacteria
can use this form.
A. Such bacteria live in the soil and on the roots of plants.
B. These bacteria convert nitrogen gas into ammonium--nitrogen
fixation.
C. Other bacteria in the soil convert ammonia into nitrites and
nitrates.
3. Once the nitrites and nitrates are available,
producers (plants) can use them to make
proteins. Consumers then eat the producers
and reuse the nitrogen to make their own
proteins.
4.When organisms die, decomposers return
nitrogen to the soil as ammonia.
5.Other soil bacteria convert nitrates into nitrogen
gas--denitrification. This process releases
nitrogen into the atmosphere once again.
Nitrogen Gas in Atmosphere
Denitrification
Nitrogen Fixation
Nitrates
(NO3-)
Decomposers return
ammonia to soil
Nitrites
(NO2-)
PHOSPHOROUS CYCLE IN ECOSYSTEMS
• Phosphorus, as phosphate (PO4-3), is an essential element of life.
• It does not cycle through atmosphere, thus enters producers through the
soil and is cycled locally through producers, consumers and decomposers.
• Generally, small local losses by leaching are balanced by gains from the
weathering of rocks.
• Over very long time periods (geological time) phosphorus follows a
sedimentary cycle.
Weathering of
Phosphates in
rocks
Fertilizer
Plant Uptake
Insoluble
Phosphates
PO4
Leaching