Transcript Nitrogen Fixing Bacteria

Cycles of Matter
In all ecosystems, materials cycle
between living things and the
environment
Cycling Materials
• Living things incorporate substances
– by eating
– during respiration and photosynthesis
• When they die, they are broken down by
decomposers and the materials are returned to
the environment
• Materials also return to environment through
excreted wastes such as feces, and urine, and
the gases given off during respiration and
photosynthesis
The Water Cycle
Water Cycle
• Water cycles from the
surface of the earth to the
atmosphere and back again
– Evaporation: from bodies of
water to become water vapor
– Transpiration: giving off
water vapor by plants through
their leaves
– Precipitation: (rainfall)
gaseous water condenses to
liquid form
– Respiration: water is a waste
product of cellular respiration
Nitrogen Cycle
• Nitrogen is an element necessary to form
amino acids and proteins as well as
nucleic acids like DNA and RNA
So How Does Nitrogen Get to
Living Things?
• Green plants need
nitrogen to
synthesize plant
proteins
• Animals get nitrogen
by eating plants or
other animals that
eat plants
• 80% of Atmosphere is nitrogen gas (N2)
• Most organisms can’t use elemental
nitrogen (N2) directly from the air
• It needs to get “fixed” into usable
compound by bacteria
The Role of Bacteria
• Nitrogen Fixing
Bacteria:
– Convert N2 in air to
ammonia (NH3)
– Often live in symbiotic
relationship with certain
plant root nodules
– Ex: Legumes:
(peas, bean, clover)
have nodules on roots
containing nitrogen fixing
bacteria
• Bacteria of Decay:
(Decomposers)
– convert nitrogenous wastes into
ammonia (NH3)
• Nitrifying Bacteria:
– convert ammonia (NH3) to
nitrates (NO3) which can then
be used by plants
– Note: most plant fertilizers
contain nitrates.
• Denitrifying Bacteria:
– convert nitrates (NO3) and
ammonia (NH3) back into N2
gas
Nitrogen cycle short clip:
http://www.youtube.com/watch?v=IaGNSmQQmBc&s
afe=active
Carbon, Hydrogen and Oxygen
Cycles
• Cycled through the processes of Photosynthesis
and Cellular Respiration
– The products of one process are reactants of the other.
• Photosynthesis (carbon fixation): takes in
CO2 from air and “fixes” it into high energy
organic compounds like sugar
• Cellular Respiration: returns CO2 to the air
as carbon compounds get broken down into
CO2 and water
•
•
Video: The Carbon Cycle
http://www.youtube.com/watch?v=irwRzQNS-GI&safe=active
• Animals eat plants and other animals and thus
take in carbon compounds.
• Dead animals get broken down by decomposers
which release CO2 to atmosphere through
respiration.
• Thus:
The level of CO2 in the atmosphere remains
fairly constant.
Global Warming
• Burning of fossil fuels (oil, coal, gasoline)
has increased the amounts of CO2 in the
atmosphere drastically since the 1800’s
• The Greenhouse Effect
– The CO2 in the atmosphere retains heat
reflected by the earths surface trapping it
– Gradually this warms the earth
– Ice caps gradually melt
– Raises ocean levels
–
http://www.youtube.com/watch?v=Hi3ERes0h84&safe=active
Tiny Biosphere
Artificial Human Biosphere
• Biosphere 2 Biomes:
• http://www.youtube.com/watch?v=qBBto9
OrZXs&safe=active
• Making Your Own Biosphere:
• http://www.youtube.com/watch?v=56IQy30CB4&safe=active
• http://www.youtube.com/watch?v=v1Fu4Bv1qg&safe=active
Carbon Cycling
Nutrient Limitation
• If ample sunlight and water are available,
the primary productivity of an ecosystem
may be limited by the availability of
nutrients. (Like phosphorus and nitrogen)