Download Nitrogen and Phosphorus Cycles

Nutrient Cycles
Nitrogen and Phosphorus
WHY DO WE NEED NITROGEN??
– Nitrogen is needed to make up DNA and
protein!
• In animals, proteins are vital for muscle function.
• In plants, nitrogen is important for growth.
NITROGEN
Nitrogen “stores”
Largest store = atmosphere (N2)
Also stored in....
• Oceans
• Organic matter (in soil)
NITROGEN
78% of the planet’s Nitrogen is N2 (atmosphere)
there are 3 main ways that nitrogen is made
available to plants/ animals....
#1 – Nitrogen Fixation
– This is a process that changes N2 into forms that
plants can use!
(nitrate)
(ammonium)
Happens in
atmosphere...
LIGHTNING!
Happens in soil,
and in water
bodies
Lightning provides the energy
for nitrogen to react with
oxygen in the atmosphere!
Nitrogen-fixing
bacteria in the soil can
convert (“fix”) N2 to
ammonium.
Nitrogen-fixing
cyanobacteria in
water can also do
this!
In the water
In the soil
Rhizobium
Usually live on roots of legumes
and other plants.
Video
Nitrogen fixing
Inbacteria
the soil – are an example of SYMBIOSIS!!
 These bacteria grow on the root nodules of
legumes like peas.
 The plants provide sugars, while bacteria
provide nitrogen ions.
#2 – Nitrification and #3- Uptake
In the soil, nitrifying bacteria convert:
NH4+  NO2-  NO3Nitrate can be
taken up by plant
roots! (Uptake)
So, plants that don’t live with
nitrogen fixing bacteria, can also
get nitrogen from the soil.
The Nitrogen Cycle
How does N2 get back to the atmosphere?
Denitrification = changes NO3- back to N2
This occurs in aquatic and land
ecosystems by denitrifying
bacteria
• Excess nitrogen dissolves in water, enters the
waterways, and washes into lakes and oceans.
The nitrogen
compounds
eventually become
trapped in
sedimentary rocks
and will not be
released again
until the rocks
undergo hundreds
of years of
weathering.
The Nitrogen Cycle
• Human activities can also affect the nitrogen
cycle.
– Due to human activities, the amount of nitrogen
in the ecosystem has doubled in the last 50 years.
– Burning fossil fuels and treating sewage releases
nitrogen oxide (NO) and nitrogen dioxide (NO2).
• Burning also releases nitrogen compounds
that increase acid precipitation in the form
of nitric acid (HNO3).
Acid rain damaged these trees
• Agricultural practices often use large
amounts of nitrogen-containing fertilizers.
– Excess nitrogen is washed away, or leaches, into
the waterways.
• This promotes huge growth in aquatic algae called
algae blooms.
• Algae blooms use up all CO2 and O2
and block sunlight, killing many aquatic organisms.
• Algae blooms can also produce neurotoxins that
poison animals.
A nice summary...
The Phosphorus Cycle
• Phosphorus is essential for life processes in
plants and animals.
– Phosphorus is a part of the molecule that carries
energy in living cells = ATP (cellular respiration)!!
The Phosphorus Cycle
• How do plants and animals use phosphorus?
Plants
Developing healthy
seeds, root
growth, and stem
strength!
Corn with a
Phosphorus deficiency
Animals (humans)
Developing healthy
bones (works with
Ca to build bone
tissue)
Where do we find P?
• It is not stored as a gas
in the atmosphere like C
and N....
• P is stored in phosphate
rock and sediments on
the ocean floors
(Phosphates: PO43-,
HPO42-, and H2PO4-)
How it gets from rock  soil
Phosphorus is released from rock into the
soil by a process called “weathering”
CHEMICAL
PHYSICAL
-Acid rain
- Chemical in
lichens
-Wind, rain,
freezing
Weathering = rock breaks down into smaller pieces.
These pieces make their way into the soil.
The Land Cycle
• Plants take up phosphate through their
roots
• Animals eat the plants (get phosphate)
• Decomposers return it to the soil
The Aquatic Cycle
• Phosphate gets into the
water by erosion,
leaching, run-off
• Most settles at the
bottom (turns into
sediment)
• Some phosphate is
taken up by aquatic
plants
Geological Uplift
• Mountains and hills are created when
rock gets “uplifted”
• The earth’s crust folds (very slowly) and
deeply buried rock layers rise up
Mt. Everest is made
of limestone that
must have originally
formed on ancient
sea floor. It contains
fossils of marine
creatures.
This is a rock in Scotland. Below the yellow line was once horizontal rock. It has
been uplifted over time. It has now started to erode due to weathering.
Human Activity & the P
Cycle
• We affect the P cycle by:
– Mining phosphate rock (for
fertilizers and detergents)
– Making fertilizers and
detergents (industrial waste)
– Applying fertilizer to land
– Fishing (remove aquatic
organisms – small effect)
A Nice Summary
How Changes in Nutrient Cycles
Affect Biodiversity
• Any significant changes to any of these
nutrients (C, H, O, N, or P) can greatly affect
biodiversity.
– Carbon cycle changes contribute to climate
change and global warming.
• Slight temperature fluctuations and changes in
water levels can drastically change ecosystems.
• Changes influence other organism in the
food webs.
How Changes in Nutrient Cycles
Affect Biodiversity
– Increased levels of nitrogen can allow certain
plant species to outcompete other species,
decreasing resources for every species in the food
webs.
– Decreased levels of phosphorus can inhibit the
growth of algae that are very important
producers in many food chains.