Transcript Science1206 Environmental Stress and Soil

Science1206
Final topics and review
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The atmosphere is a mixture of particles and gases
which provides air, retains heat that warms the
Earth, and has a layer of ozone that protects us
from UV radiation.
The atmosphere is made up of several layers. Two
regions: the troposphere and the stratosphere are
relatively closer to the Earth than the others.
•The troposphere extends from the Earth's surface
to an altitude as high as seventeen kilometers
above the Earth. In this region the temperature
decreases as altitude increases.
•The stratosphere is located above the troposphere
to about fifty kilometers above Earth and the
temperature increases as altitude increases.
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Sources of Water Pollution
Water pollution is any physical or chemical change in surface or
ground water that can harm living things.
Five categories:
1) Organic solid waste
2) Disease causing organisms
3) Inorganic solids and dissolved minerals
4) Heat
5) Organic chemicals
Water is defined by its intended use. There are three main
indicators of water quality:
1) Bacteria count
2) Concentration of dissolved oxygen
3) Biochemical oxygen demand
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Bacteria
Detection is expensive and difficult. Detecting coliform
bacteria is used to see if disease causing bacteria is present.
The presence of coliform bacteria indicates that more
dangerous bacteria may be present.
Dissolved Oxygen
Different solutions are used to test for oxygen. They change
color in the presence of oxygen. Another way is to examine
living things in the water. Trout indicate high oxygen levels.
Catfish and carp indicate low oxygen levels.
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BOD Biological Oxygen Demand
This is the measure of the amount of dissolved oxygen
needed by decomposers(bacteria) to breakdown the organic
matter in a sample of water over a 5 day period at 20 degrees
C.
It indicates the amount of available organic matter in a water
sample. As the number of organisms in an ecosystem
increases, so does the BOD.
A productive lake with many living things will have a high
BOD. As the number of organisms increases and biological
demand increases , more organisms use oxygen from the
water. This will cause dissolved oxygen to drop.
(eg. Low value=2 mg/L; high value= 20 mg/L)
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Sewage, Decomposers and Oxygen Levels
Too many nutrients can create problems for lakes.
For example when raw sewage is released into an aquatic
ecosystem.
The greater the amount of decaying matter introduced
into the water, the greater will be the population of
decomposing bacteria.
Both bacteria and fish use oxygen, and fish will die if
oxygen levels drop too low.
Dead fish create detritus which further promotes
bacteria growth. To prevent damage to ecosystems cities
install water treatment plants.
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Aquatic eutrophication
 One of the factors that determines how many of these
microscopic organisms live in the water is the availability of
nutrients.
 The nutrients that have the most profound effect on the
number of microorganisms found in the water are nitrates
and phosphates. Low levels of nitrates and phosphates reduce
the number of micro-organisms. The water appears clear and
sunlight can penetrate deeper supporting the production of
oxygen by photosynthetic organisms.
 Under these conditions, the pond or lake can support large
populations of fish and other organisms that are adapted to
relatively high levels of oxygen. Such a lake in which oxygen
levels are relatively high is known as an oligotrophic lake.
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Aquatic eutrophication
• Bodies of water enriched by nitrates and phosphates
mainly from agricultural lands and from untreated
human or animal sewage causes the number of
micro-organisms to increase to the point that the
water actually appears turbid (cloudy). As a result of
the bacteria, less light is able to penetrate the water
and oxygen concentrations tend to be reduced. Such
a lake is said to be eutrophic.
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Go to Work
• Read 4.2 "Sources of Water Pollution" on pages 132 134.
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Short Term Stress and Long Term Stress
Describe what is meant by short term stress and long term change
Identify factors that cause extinction of animals including: influence
of humans, climate change, and pressure of competition
Compare a natural and an artificial ecosystem in terms of the
influence of different abiotic factors on the organisms that live there
Describe how acid deposition affects a forest ecosystem
Describe how the introduction of an exotic species (zebra mussel)
has affected life in the great lakes
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• The way that a population responds to short term stress
and long term change depends on the ability of the
organisms within the population to continue to meet their
biological needs for appropriate range of climatic
conditions (temperature, light, moisture), food, water,
shelter, space, and opportunity for reproduction.
• Most organisms are capable of withstanding a loss of one
or more of these factors for a short period of time, but will
die if one or more of these biological needs is not met for a
long period of time. Some populations may become extinct
as a result of long term change.
Examples of short term stress include
seasonal peaks in temperature, sudden
changes in water supply, or sudden but
limited human impact.
Climate change (global warming), infestation by
foreign plants and animals (exotic species), and
permanent human influence (habitat
destruction, acid deposition, etc.) are examples
of
long term change.
Pine Marten
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Keystone Species
• A keystone species is one considered so important to
the stability of the ecosystem, that if there was a
decline in that species, the community would not be
able to maintain its stability and may even collapse.
• Nearly any arctic organism could represent this
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Killer Whale
Prairie dog
European Beaver
Flying Fox
Grizzly Bear
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