Download HTHS Change and Sustainability

Change and Sustainability
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Importance of Soil
• Soil: the layer of material that covers the
land
– Where plants anchor and grow
– Made of weathered rock, decomposing plant
and animal matter
– Has spaces for air and water movement
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Layers of composition
• 3 major types of soil
– Horizon A:
– Horizon B:
– Horizon C
• Each layer has
different
characteristics
depending on where
it is found.
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Grasslands
• Horizon A is deep and
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supports root growth
Horizon B is the
subsoil (mix of dirt
and rock)
Horizon C is mostly
rock formation
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Forest
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Deserts
• Horizon A: limited
plant growth so little
decomposition, so
thin top soil or none
at all.
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Biological Community
• Interactions between
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plants and animals
Includes food chains
and life cycles within
the soil.
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Nitrogen Cycle Explained
• Nitrogen is critically important to life, as it is a
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basic building block for amino acids and
proteins.
The chief reservoir of nitrogen is the
atmosphere, which is about 78% nitrogen.
Nitrogen gas in the atmosphere is composed of
two nitrogen atoms bound to each other.
Nitrogen is a fairly non-reactive gas; it takes a
lot of energy to get nitrogen gas to break up
and combine with other elements, such as
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carbon or oxygen.
Nitrogen Fixation
Nitrogen gas can be taken from the atmosphere (fixed
- reacted) in two basic ways.
• 1. Lightning provides enough energy to "burn" the
nitrogen and fix it in the form of nitrate, NO3-. This
process is duplicated in fertilizer factories to produce
nitrogen fertilizers.
• 2. Nitrogen fixing bacteria use special enzymes to fix
nitrogen (react the nitrogen with oxygen or
hydrogen). The NH4+ produced is converted to NO3by nitrifying bacteria found in the soil.
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The Cycle Begins
• 1. Most plants can take up nitrates and convert
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it to amino acids and then possibly proteins.
2. Animals acquire all of their amino acids when
they eat plants (or other animals).
3. When plants or animals die (or release waste)
the nitrogen is returned to the soil.
4. The nitrogen that is usually returned to the
soil in animal wastes or in the output of the
decomposers, is ammonia. Ammonia is rather
toxic.
5. Nitrifying bacteria in soil or water convert
ammonia to nitrates, which are taken up by
plants to continue the cycle.
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Cycle Completed
Soil also contains bacteria the uses NO3- as
a fuel source. These Denitrifying Bacteria
release N2 back to the atmosphere.
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Disturbing soils
• Soils change over
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time naturally
Human impact:
deforestation leads to
increased erosion of
topsoil (no roots to
hold soil in place)
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Feeding the Human
Population!
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Productivity of Ecosystems
• Ecosystems have different productivities,
based on light availability, soil types,
precipitation, temperature, nutrients.
• Productivity: the quantity of biomass of
plants produced each year on a given area
(g/m2)
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Productivity of different ecosystems:
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Sustaining life
• Biotic: living part of
the environment. Ex:
plants and animals
• Abiotic: non-living
part of the
environment. Ex:
elements, air, and
water.
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The key events - respiration and photosynthesis
• Respiration takes
carbohydrates
and oxygen,
combines them
to produce
carbon dioxide,
water, and
energy.
•Photosynthesis takes
carbon dioxide, water
and energy to
produce
carbohydrates and
oxygen.
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CO2 + H2O
C6H12O6 + O2
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• Photosynthesis starts with water
present in the soil and carbon
dioxide from the atmosphere (the
product of respiration,
combustion).
• Chlorophyll is the green pigment in
plants (gives them their color). This
uses the light from the sun as the
energy needed to transform carbon
dioxide and water into sugar (made
into starch, cellulose and lignin –
woody fiber).
• Photosynthesis also produces
oxygen which the plant releases
into the atmosphere.
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The cell works constantly to stay alive.
• It constructs macromolecules
• It transports substances into and out of the cell
• It moves (some cells)
• It grows
• It reproduces
To accomplish these tasks and many others, the
cell needs energy that it must get from it’s
environment. We know that the sun is the
energy for plants and other photosynthetic
organisms, but what about the consumers?
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What happens to the Carbon?
• Plants take up carbon dioxide and convert it into
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carbohydrates through photosynthesis.
This carbon in the plants now has 3 possible
fates:
(i) it can be liberated to the atmosphere by the
plant through respiration;
(ii) it can be eaten by an animal,
(iii) it can be present in the plant when the plant
dies
Animals obtain all their carbon from their food,
and, thus, all carbon in biological systems
ultimately comes from plants (autotrophs).
In the animal, the carbon has the same 3
possible fates as in plants.
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• heterotrophes.
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use organic
molecules in
their food to get
the energy they
need.
Respiration uses
the sugar in
food to make
energy. The
byproducts of
respiration are
water and
carbon dioxide.
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Water is one of the components needed for
photosynthesis and a very important component in
living things. How is water cycled around the earth?
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Ecological Footprints
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What impact do humans have on the earth?
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The Ecological Footprint of a population is
equal to:
Area of land and water occupied by the
population
+
Land and water used to produce resources
for the population
+
Land and water used to dispose of wastes
for the population
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-1000m2
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The Food we Eat
The food we eat contributes 11 percent of
the total household output of greenhouse
gases which cause global warming;
21 percent of common and 13 percent of
toxic air pollution;
47 percent of common and 26 percent of
toxic water pollution;
and 78 percent of aquatic and 54 percent of
terrestrial habitat alteration
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• Most of the world's fresh water and land is used
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in agriculture.
Our North American diets are particularly water
intensive. It takes 5,020 liters of water per person
per day to produce what we eat. Compare this to
2,810 liters per person per day in Latin America,
2,530 liters in China, and 1,760 liters in Africa.
Much of this difference is accounted for in the
quantities of meat (production and processing of
meat takes a lot of water) and irrigated crops we
eat.
• Meat production and processing contributes four
times more water pollution than fruits, veggies
and grains.
• Pesticide contaminants to water are roughly the
same in both categories.
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• Livestock production in Canada over the past five years
has increased, in some cases dramatically (cattle 4.4%,
pigs 26,4%, chickens 23.4% and sheep 46%), and the
per capita demand for meat worldwide is growing. This
has led to the development of giant feedlots or megabarns where animal husbandry is replaced by
mechanized production. Unlike the traditional mixed
farms where livestock raised was well-matched with
crops that could use the manure, these feedlots
generate huge amounts of liquid manure that must be
stored and disposed of. Most often, the volumes of
manure overwhelm the ability of local cropland to
absorb it all safely. Gigantic liquid manure lagoons can
leak or rupture, contaminating groundwater, streams,
rivers and estuaries with nitrates, phosphates,
antibiotics and other drugs, and disease vectors like
bacteria and viruses. Factory farms are also a source of
toxic air pollution and noxious odours.
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• Aquaculture has developed along the same trajectory.
Over 20 years, small family fish farms including those in
the Bay of Fundy have become huge industrial-scale
feedlots with control or ownership increasingly
concentrated in a few large hands. Chemical inputs drugs, pesticides, feed contaminants, anti-foulants, dyes and fish excrement have become a huge source of
pollution to coastal waters where aquaculture is practised.
Now even shellfish aquaculture is growing so large that
there are localized impacts on the seafloor.
• Industrial scale growing of monoculture crops also has a
huge environmental impact. Overworked soils cause
irreplaceable topsoil to erode and soil health to decline.
Chemical fertilizers used to compensate for degraded soil
pollute groundwater and surface water. Toxic pesticides
used to control insects and kill weeds inject poisons into
the air, water and food we eat. This chemical-dependent
crop production has become dominant over the past thirty
years.
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Succession
• One ecosystem is gradually replaced by
another over time.
• Primary succession:
– Sequence of changes that begins with bare
landscape and ends with a climax community
– Climax community is one at maximum
productivity and support
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Secondary Succession
• Restores a community back.
• Ex: fire
• Fire will destroy a forest, but over a 10
year period that forest can return to its
original state.
• Quicker than primary succession
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Irreversible Change
• Frequent and severe
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change can cause the
destruction of any
ecosystem
Remediation: can be
restored so it is
suitable for wildlife
and forestry
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Protecting land
• Wetlands:
– Believed by humans to
be worthless because
could not use for
farming or building
home/business
– Humans changed the
land to be useful, so
they drained the water
and filled in the land
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• Would this affect the
environment? Yes!
– Wetlands act like
sponges, holding in
lots of water, but
slowly releasing it
when needed.
– They improve water
quality by trapping
(filtering) particles
out.
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• Wetlands provide
peat (a valuable
source of nutrients)
– Can be used for soil
improvement
– Burned as a fuel
source
• Peat is sold for lots of
money ($100 million a
year)
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Protecting Wetlands
• Loss of an area leads
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to loss of the entire
ecosystem (plant and
animal biodiversity)
Loss for the scientific
community
Loss for cultural
groups that consider
the land sacred.
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