The Cycling of Matter
• To understand how matter cycles through
ecosystems, you must understand the cycling of
organic substances in living things.
• The materials stored in living things comes from a
limited amount of matter.
• Therefore, all matter must be recycled. This
recycling of matter involves the carbon, oxygen
and nitrogen cycles as well as the role of
decomposers.
• All matter tied up in the bodies of organisms
must be decomposed and recycled.
• organic substance- compound that always
contains carbon and hydrogen atoms, and
often oxygen and nitrogen atoms. e.g.
proteins, sugars,
– e.g. C6H12O2, CH4
• inorganic substance - compounds that don’t
contain a combination of hydrogen and
carbon.
– e.g. CO2 , H2O
Carbon Cycle
• carbon is the main atom of all living things. In inorganic
form it mainly exists as carbon dioxide gas in the air.
CO2 is also dissolved in sea water.
• plants use carbon during photosynthesis to make
carbohydrates. This takes carbon from its inorganic
state and transforms it into organic compounds. This
carbon then gets passed up the food chain
• carbon is returned to its inorganic state when
organisms digest food to get energy. Consumers use
sugars in a cell reaction process called cellular
respiration.
• Cellular respiration requires oxygen. This reaction
releases energy to the body and gives off inorganic
carbon dioxide to the air.
• Decomposer organisms also release carbon dioxide to
the air
• some carbon has become buried as coal. This carbon is
locked away out of circulation unless humans release it
by burning fossil fuels (gas, oil, coal).
• These fossil fuel deposits, the ocean and boglands are
huge reservoirs of carbon which are released slowly to
the atmosphere.
Human Impact on the Carbon Cycle;
• the level of CO2 in the atmosphere is rising
quickly way beyond normal levels. This is due to:
• 1. carbon released from natural reservoirs faster
than normal due to burning of fossil fuels,
burning forests.
• 2. less CO2 being removed due to removal of
plants to clear land for agriculture, forestry or
building.
• The result has been global warming
Global Warming
• global warming - a warming trend in our climate caused by
excess greenhouse gases such as carbon dioxide.
• Greenhouse gas - any atmospheric gas that traps heat and
adds to the greenhouse effect.
– e.g. carbon dioxide.
• CO2 in the atmosphere provides a natural “greenhouse
effect”. It traps reflected solar energy and warms the earth.
However, since humans have increased the amount of CO2
in the atmosphere, we are causing too much heat to be
trapped and it is changing our weather patterns and
climate. The average global temperature is rising.
Your Turn
• Do questions p. 65, # 1, 2, 4, 6, 7 (a) (b) (c)
The Nitrogen Cycle
• Nitrogen is needed by all organisms to make proteins
(tissue) and DNA. 79 % of the air is nitrogen gas but plants
and animals cannot get their own nitrogen from the air.
• Only plants can use inorganic forms of nitrogen such as
nitrates, NO3 , found in the soil or dissolved in water, and
extract - the nitrogen in them to use in making their own
plant proteins.
• All consumers must consume other organisms to get their
proteins.
• When organisms die, the nitrogen present in the proteins
of living things gets recycled back into inorganic forms such
as ammonia, nitrites and nitrates by the processes of
decomposition and denitrification.
• Nitrogen - fixation stage
• nitrogen fixation - the process of converting free atmospheric
nitrogen into nitrates.
• Nitrogen gas in the atmosphere gets converted into nitrates, NO3 .
These are absorbed by the - roots of plants. This can occur in two
ways:
• (1) lightning in the atmosphere - causes nitrogen in the air to react
with oxygen to form nitrates.
• (2) Nitrogen - fixing bacteria - give off nitrates as a waste product.
Some nitrogen fixing bacteria are free - living but many live in the
roots of certain plants called legumes. They supply the legume
plants with a steady supply of nitrogen in return for shelter in the
roots and food. Legumes include beans, alfalfa and clover - type
plants
Man’s Impact on the Nitrogen Cycle;
• We are adding extra nitrogen to many
environments in the form of fertilizers and
pollution wastes from many industries.
• Human sewage is often released into rivers with
little treatment(e.g. Montreal into the St.
Lawrence River) and act as fertilizer.
• Normally, there is a balanced amount of nitrate in
an aquatic ecosystem. However, in areas near
agricultural lands where lots of fertilizers are
used, runoff into rivers have caused the levels of
nitrate in lakes to get too high.
• this causes a process called eutrophication - pollution
making a lake richer in nutrients.
• If the level of nitrate gets too high, an algal bloom can
occur. This is where the algae population grows out of
control, scumming over much of the lake’s surface.
• The algae, too many in number, block much of the light
from reaching other plants growing underwater.
• Also, when the algae die, the decomposer bacteria in
the water have lots of food. This causes their
population to increase.
• All this extra decomposition uses up much of
the dissolved oxygen in the water. This is very
unhealthy to the ecosystem.
• It has a bad effect on many species, causing
their numbers to decline. Fish and other
aquatic animals may begin to die.
Decomposition stage
• Decomposer bacteria decay dead organisms.
They break down the proteins in the dead
organisms to produce ammonium.
• Other bacteria in the soil convert ammonium
into nitrites. Another type of bacteria convert
the nitrites into nitrates, becoming available
again for plant use.
Denitrification stage
• Some of the nitrates in the soil is converted
back into free nitrogen gas by certain bacteria
called denitrifying bacteria. This returns
nitrogen to the atmosphere.
Your Turn
• Do -questions, p. 69, # 1 - 4 and p. 71, # 3,4
The Oxygen Cycle
• Oxygen is cycled between the atmosphere and living
(biotic) things. Oxygen is used in the process of cellular
respiration by both plants and animals. Carbon is
released in the form of CO2 as a waste product of this
reaction.
• Plants take in the inorganic gas CO2 and use it in the
process of photosynthesis to make organic sugars such
as glucose, C6H12O6. Oxygen is released as a waste
product of the photosynthesis reaction.
• The reactions of cellular respiration and photosynthesis
are reciprocals of each other. The reactants of one
reaction are the products of the other reaction.
Photosynthesis:
CO2 (g) + H2O (l) → C6H12O6 (s) + O2 (g)
Cellular Respiration:
C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
• C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
Reaction
Reactants
Products
Photosynthesis
Carbon dioxide + water
CO2 + H2O
glucose sugar + oxygen
C6H12O6 + O2
Respiration
glucose sugar + oxygen
C6H12O6 + O2
Carbon dioxide + water
CO2 + H2O
Human Impact on the Oxygen Cycle
• Deforestation is the major impact by man.
Trees are the earth’s largest oxygen –
producing plants. Plants give off O2 to the
atmosphere through photosynthesis. The
destruction of forests lowers the amount of
CO2 which is being converted into O2. The
reduction in trees is a one of the contributing
factors to global warming.
Your Turn
Case Study : The Effects of Deforestation on
Cycling
• p. 72 - 73 do items (b) - (g).
• p. 73, # 1 - 3.
The Biomes of Canada (read pp. 88 92)
• Biome - a collection of ecosystems that are
similar or related to each other, usually by the
types of plants present in the area.
There are 4 biomes present in Canada:
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1. Tundra
2, Boreal Forest
3. Temperate Deciduous Forest
4. Grasslands
Tundra
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p. 88 - Know Table 1, p. 89
Also:
- permafrost and active layer
- why no trees grow there
- dominant plants?
- why slow decomposition rate?
- why few animal species are present
Boreal Forest Biome
• - know table 2, p. 90
• - Also:
• - dominant plants : conifers ( needle - leafed trees
which produce cones) eg. spruce, fir,pine.
• p. 89 - makes up 80% of forests in Canada
• - explain why soils are acidic here
• - explain how conifers are adapted to the extreme
climate here
• p. 90 - explain why food available in this to animals
living in the lower layer of this biome is limited
Temperate Deciduous Biome: pp. 91 92
• p. 93 - know Table 3, p. 92
• p. 91 - know where its located
• p. 91 - why is there faster decomposition here than in
the Boreal?
• p. 91 - Why do more plants grow under the large trees
of this biome than in the Boreal?
• p. 91 - Why can the temperate deciduous forest
support more many more animals than the Boreal
forest?
• p. 91 - Describe the layers present in the temperate
deciduous forest. Compare this to the Boreal Forest.
Grassland Biome:
• p. 91 - Why does the temperate deciduous forest contains greater
biodiversity than the Boreal
• forest?
• p. 93 - know Table 4
• p. 92 - Grasslands are at a similar latitude as the Temperate
deciduous forests but are different in terms of their dominant
plants. Explain why.
• p. 92 - Explain why trees don’t tend to grow on the grasslands.
• p. 92 - Explain why the grassland soil is the most fertile soil in the
world.
• p. 92 - Explain why the biodiversity of grasslands is low in
comparison to the Temperate Deciduous forest and the Boreal
forest.
• DO: questions, p. 93 - # 1 - 5, 8