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Plants play a crucial role in the carbon
cycle because they
a. do not release carbon dioxide during
cellular respiration.
b. allow carbon to enter an ecosystem
through photosynthesis.
c. have special bacteria that live in their
root systems.
d. are chemically converted into fossil
fuels when burned.
Which item is a carbon sink and not part of the
carbon cycle?
a. carbon in the atmosphere in the form of
carbon dioxide
b. consumers breaking down carbohydrates into
carbon dioxide during respiration
c. carbon found within limestone rocks
d. carbon dioxide being converted into
carbohydrates during photosynthesis
 Which of the following is not a true
statement about cellular respiration?
 a. It is essentially photosynthesis in
reverse.
 b. Oxygen is one of the primary
reactants.
 c. It produces energy for organisms to
use.
 d. Sugar molecules are its primary
products.
We use but don’t always reuse.
 We recycle paper, metals, water, etc.
 We recycle almost 50% of paper
in U.S. – about 42 million tons.
 But ecosystems constantly re-use
carbon, nitrogen and phosphorus.
All life is based on the element CARBON.
Carbon is the major chemical
constituent of most organic matter,
from fossil fuels to the complex
molecules (DNA and RNA) that
control genetic reproduction in
organisms.
Carbon Cycle
 Carbon is found in protein, fats, and sugars/carbohydrates.
 Carbon cycles between the atmosphere, land, water, and
organisms.
Carbon is stored on our planet in the
following major sinks:
(1) as organic molecules in living and dead organisms found in
the biosphere;
(2) as the gas carbon dioxide in the atmosphere;
(3) as organic matter in soils;
(4) in the lithosphere as fossil fuels and sedimentary rock
deposits such as limestone, dolomite and chalk; and
(5) in the oceans as dissolved atmospheric carbon dioxide and as
calcium carbonate shells in marine organisms.
Carbon Cycle
Short-term carbon cycle
Like most everything it starts with producers:
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Plants produce carbohydrates (glucose) by photosynthesis.
Consumers eat the plants.
Consumers break down glucose by cellular respiration.
Energy is released back into the atmosphere.
Short-term carbon cycle
 Carbon is released from ecosystems as carbon dioxide gas
by the process of respiration.
 Respiration takes place in both plants and animals and
involves the breakdown of carbon-based organic molecules
into carbon dioxide gas and some other compound by
products.
 The detritus food chain contains a number of organisms
whose primary ecological role is the decomposition of
organic matter into its abiotic components.
Long-term Carbon Cycle cont…
 Unused carbohydrates are stored as fat and oil.
 Carbon returns to the soil after organism’s death.
 Over time this turns into coal, oil, natural gas.
 Fossil fuels
How Humans Affect the Carbon
Cycle
http://www.youtube.com/watch?v=c40jebr9jbg
 Burning fossil fuels releases 6 billion tons CO2 into the
atmosphere.
 Trees can remove CO2 from the atmosphere.
 This can contribute to global warming.
Long-term Carbon Cycle
 When consumers eat, some carbon is stored.
carbonates = bones and shells
 Over millions of years carbonates turn into limestone.
largest reservoir/storage of carbon
How Humans Affect the
Carbon Cycle
 Since the Industrial Revolution, humans have increased the
quantity of carbon dioxide found in the Earth's atmosphere
and oceans by over 30%.
 Major sources of this gas due to human activities include
fossil fuel combustion and deforestation and habitat
destruction.
 Emissions from fossil fuels account for about 65% of the
additional carbon dioxide currently found in the Earth's
atmosphere. The other 35% is derived from deforestation and
the conversion of natural ecosystems into agricultural
systems.
Which item is a carbon sink and not part of the
carbon cycle?
a. carbon in the atmosphere in the form of
carbon dioxide
b. consumers breaking down carbohydrates into
carbon dioxide during respiration
c. carbon found within limestone rocks
d. carbon dioxide being converted into
carbohydrates during photosynthesis
The Nitrogen Cycle
 Organisms need nitrogen to build proteins that are needed
to build cells.
 Nitrogen makes up 78% of the atmosphere (about one
million times more than the total nitrogen contained in
living organisms), but most organisms cannot use it in this
form.
 Other major stores of nitrogen include organic matter in
soil and the oceans. In most ecosystems nitrogen is
primarily stored in living and dead organic matter.
Nitrogen Cycle cont…
 Nitrogen is cycled between the atmosphere, bacteria, and
other organisms.
 Bacteria live in the roots of legumes (beans, peas, and
clover) in nodules. In exchange for some nitrogen, the
bacteria receive carbohydrates from the plants.
 Some bacteria live in the soil and put nitrogen in the soil.
 Plants use nitrogen in soil, consumers eat plants, and so
on…
The Nitrogen Cycle
The Nitrogen Cycle
 Almost all of the nitrogen found in any terrestrial ecosystem
originally came from the atmosphere. Significant amounts enter
the soil in rainfall or through the effects of lightning.
 The majority is biochemically fixed within the soil by
specialized micro-organisms like bacteria, actinomycetes, and
cyanobacteria.
The Nitrogen Cycle
Decomposers in the Nitrogen Cycle
 After bacteria convert nitrogen, plants use the nitrogen and
consumers eat plants.
 Decomposers help return nitrogen back to the atmosphere
by breaking down urine, dung, leaves, dead plants and
animals.
Phosphorus Cycle
 Needed for bone and teeth formation
 Plants get phosphorus from soil and water;
consumers get phosphorus from plants.
 Moves from environment to organism to
environment;
usually not in the atmosphere.
The Phosphorus Cycle
Phosphorus Cycle cont…
 Phosphorus enters the soil when rock erodes.
 Returns through waste and decomposing organisms.
 Some phosphates get washed out to the ocean and deposit
on the ocean floor.
Fertilizers
 Contain phosphorus and nitrogen
 Application of fertilizers to crops has caused increased rates of
nitrate leaching into groundwater. Additional nitrogen entering
the groundwater system eventually flows into streams, rivers,
lakes, and estuaries. In these systems, the added nitrogen can
lead to eutrophication.
 Algae blooms
Last Problem
 When coal, wood, or oil are burned, nitric oxide is
released.
 Nitric oxide combines with oxygen and water vapor to
make nitric acid/acid rain.