Download File - SLHS Academic biology

KEY CONCEPT
Matter cycles in and out of an ecosystem.
Water cycles through the environment.
• The hydrologic, or water, cycle is the circular pathway of water on Earth.
• Organisms all have bodies made mostly of water.
precipitation
condensation
transpiration
evaporation
lake
groundwater
surface
runoff
water storage
in ocean
The Carbon Cycle
Carbon
• All living things are made of carbon!!!
– Plants use carbon dioxide and sunlight to make
their own food. The carbon becomes part of the
plant.
– Animals get
carbon by
eating plants,
algae, or other
animals that
have eaten
plants.
Carbon Does Not Stay Still – It Is
On the Move!
1.
2.
3.
4.
5.
In the atmosphere, carbon is in CO2.
Plants use CO2 and sunlight to make their own food.
Animals consume plants.
Plants that die may turn into fossil fuels made of carbon,
like coal and oil, over millions of years.
When humans burn fossil fuels, most of the carbon
quickly enters the atmosphere as CO2.
PHOTOSYNTHESIS
Using light energy, plants
combine CO2 from the
atmosphere and H20 to form
sugar and O2 in
photosynthesis.
sunlight
Carbon Dioxide + Water → Sugar and Oxygen
(CO2)
(H2O)
(C6H12O6)
(O2)
RESPIRATION
In respiration, the
compounds containing
carbon are broken
down, and carbon
dioxide is released.
Plants, animals, and
microorganisms all
carry out respiration!
COMBUSTION
• Most of the CO2 is
produced during the
process of burning called
combustion.
• When compounds
containing carbon (wood,
coal, or oil) are burned,
CO2 is released.
• The use of CO2 by plants during
photosynthesis is a much slower process.
• As a result of the imbalance between
these two processes, the level of CO2 in
the atmosphere is increasing.
Decomposers
• When organisms die, decomposers break down
the carbon compounds in their bodies, and CO2
is returned to the atmosphere.
• During decomposition
(decay), other
chemicals are also
returned to the soil
or released into the
air. One of these
chemicals is
nitrogen.
When organisms die, decomposers break down the carbon
compounds in their bodies, and carbon dioxide is returned to
the atmosphere.
• What process uses carbon
dioxide and produces
oxygen?
• What two processes
produce carbon dioxide?
• What process produces
most of the carbon dioxide
in the atmosphere?
• By what process do
decomposers return carbon
dioxide to the atmosphere?
The Nitrogen Cycle
NITROGEN
• Plants and animals need
nitrogen to make protein.
• The air is about 78%
nitrogen, but plants and
animals cannot use nitrogen
directly from the air.
How Do Plants Get Nitrogen?
• Special bacteria, in the soil
and water, must change or
“fix” nitrogen gas (N2) into a
form that plants can use.
• These bacteria are called
nitrogen-fixers.
N=N → 2NH3
Nitrogen Fixers
• Mutualistic Relationship
– The plants provide food and cover for the
bacteria, and the bacteria convert nitrogen
gas into fertilizer for the plant.
How Do Animals Get Nitrogen?
• Animals get nitrogen from plants or from
other plant-eating animals, in the form of
protein.
Animals must
eat protein to
get their
nitrogen
requirements!
We can’t
breathe in
nitrogen!
How is Nitrogen Recycled?
Nitrogen is recycled by special bacteria that break
down the nitrogen compounds (proteins) in dead
plants and animals, and in animal wastes.
If plants do not use the nitrogen compounds as
fertilizer, special forms of bacteria may recycle it.
These bacteria convert the unused fertilizer into
nitrogen gas and release it into the atmosphere.
All natural ecosystems
depend upon
bacteria to keep the
nitrogen cycle going!
Natural and human activities can disrupt biogeochemical
cycles and ecosystems.
• Natural disruptions
–volcanic eruptions
–forest fires
–landslides and earthquakes
–living organisms
• Disruptions caused by humans
–poor farming practices
–burning fossil fuels
1. What kinds of organisms
are essential for the
nitrogen cycle?