Download The Importance of Oxygen

The Importance of Oxygen
Oxygen is necessary to support life in terrestrial and aquatic ecosystems:
The Earth's atmosphere contains about 21% oxygen (by volume). Oxygen (O2) is a
byproduct of the process of photosynthesis and is used by the consumers to carry out
cellular respiration from which energy is released from the foods they eat. Oxygen is also
required by plants because they also carry out cellular respiration to release the food
stored in their cells. Oxygen is therefore necessary for life on Earth.
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As you know from the previous lesson, oxygen gas (O2) is recycled as part of the
carbon, hydrogen, and oxygen cycles.
Oxygen gas is cycled between the atmosphere and the living organisms of both
aquatic and terrestrial ecosystems.
Oxygen gas from the atmosphere is absorbed by the water in aquatic ecosystems.
Oxygen is also produced as a byproduct of the photosynthetic organisms that live
in the aquatic ecosystems.
Heterotrophs (consumers) living in aquatic ecosystems require oxygen for cellular
respiration but they receive their oxygen from the dissolved oxygen in the water.
Ozone Protects Life from UV Radiation:
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.
The air near the Earth consists of mostly of nitrogen (78.1%) and oxygen with small
amounts of argon and carbon dioxide. Also present in the atmosphere is water vapour and
trace gases that create a "blanket" around Earth. Human activities are having drastic
effects on the atmosphere. For example, we are now more dependent on the world's
natural resources (i.e. fossil fuels) and we are creating synthetic products which have an
impact on the types of gasses emitted.
What is ozone? Ozone is a form of oxygen. In the atmosphere oxygen is found in three
forms: O, O2, and O3 (ozone). Ozone is created when solar rays hit a molecule of O2 and
cause it to split apart. If one of these free atoms hits another O2, ozone (O3) is formed. In
the stratosphere, oxygen is constantly bombarded by UV radiation resulting in the
formation of ozone (O3). Ozone serves as a protective layer, filtering out the harmful UV
radiation and thereby protecting life here on Earth from the harmful effects of UV
radiation. In recent years, human activities have lead to the destruction of the ozone layer.
This environmental problem is known as ozone depletion.
Ozone's unique properties allow it to act as a protective layer around the Earth. It acts like
a sunscreen, filtering damaging UV rays. This layer is thickest at the poles and thinnest at
the equator. Even though the sun's radiation is most direct over the equator, stratospheric
winds carry ozone towards the poles. The amount of ozone present at any give time
depends on several factors which include: temperature, pressure, and height of the
stratosphere from Earth's surface.
Geography, temperature, light, and wind contribute to the development of the ozone
layer. During cold winters in the Antarctic winds moving in a circular pattern create a
vortex and this causes the production of polar stratospheric clouds. This allows a surface
for relations which result in the release of reactive chlorine and bromine. UV radiation
triggers a reaction with the chlorine and bromine that destroys the ozone.
The Importance of Oxygen
What is depleting the ozone layer?
Chlorofluorocarbons (CFCs) account for approximately 80% of stratospheric ozone
depletion. Other compounds that contribute to ozone depletion include: halons, carbon
tetrachloride, methyl chloroform, hydrochlorofluorocarbons (HCFCs), and methyl
bromide. These are known as industrial halocarbons.
These compounds are used in refrigerators, furniture foam, fire extinguishers, etc. Human
activities also contribute to the gradual disappearance of the ozone layer such as,
deforestation, fertilizer use, and fossil fuel combustion. There are a couple of reasons
why industrial halocarbons are very effective at ozone depletion.
The first is the fact that they survive long enough to reach the stratosphere and second
they help natural reactions that destroy ozone. Once in the stratosphere, UV-C radiation
breaks up compounds releasing chlorine and bromine.
The effects of ozone depletion are not yet fully understood, but we do know that they
are potentially severe. Ozone, because of UV radiation, warms the atmosphere, however
because of the use of CFCs the levels of ozone are declining and thus the stratosphere
cools. Also, levels of carbon dioxide are on the rise globally. This traps the heat in the
lower atmosphere and causes the stratosphere to become cooler.
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Ozone depletion can have drastic effects of the environment and the organism
therein.
In humans these rays are connected to incidents of cancer in various forms. This
exposure can cause skin cancer, eye damage and cataracts, and immunosupression. Skin cancer is caused by too much sun.
UV-B radiation affects not only humans but other living plants and animals as well. The
problem for these populations is that they cannot artificially protect themselves from
these harmful rays. The destruction of phytoplankton will affect the global marine food
supply because these plants serve as food for other fish. Animals are also at risk to UV
radiation. They may develop cancer and it is the exposed parts of their body are at highest
risk.
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Ozone protection however, does not end here. It ends with you as a person.
People can protect themselves from the effects of ozone depletion by:
minimizing the ours they spend in the sun;
by wearing pants, sunglasses, long-sleeved shirts, and pants;
wearing sunscreen and;
do not expose infants and small children for extended periods of time.
Global Warming
Enhanced Global warming is the term given to describe the recent increase of the
earth’s temperature as a whole. The earth’s weather and climate is controlled by energy
from the sun, which warms the surface of the earth as it, in turn, deflects the energy back
into space. Some of this deflected energy is retained within the atmosphere of the earth
by greenhouse gases which prevent the energy from passing into space, thereby
preserving heat. It is this process that results in the earth having a temperature which
supports life. Global warming has occurred since the 1980's, and during this time, the
seven warmest years in global meteorological history have been recorded.
If the earth's warming trend continues into the next decade the earth may enter a period of
climate change unlike any of the past. Changes in the concentration of heat-trapping
gases "greenhouse gases" have played a major role, because these gases trap the heat and
does not let it escape, therefore causing global warming or an increase in climate
temperatures.
The three primary greenhouse gases which are responsible for this warming include
carbon dioxide, methane, and nitrous oxide, all of which naturally exist in the earth’s
atmosphere. These three gases are required in order for the natural process of temperature
control to occur. The problems arise when there is a surplus of these gases in the
atmosphere.
Causes of excess greenhouse gases include:
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Carbon dioxide is released into the atmosphere by the combustion of solid waste,
fossil fuels, wood and wood products.
Methane emissions are a direct result of the production and transportation of coal,
natural gas, and oil. The raising of livestock, and the decomposition of organic
waste also contribute to the amount of methane emitted into the atmosphere.
Nitrous oxide emissions are a result of agricultural and industrial activities as well
as the burning of solid waste and fossil fuels.
There are also greenhouse gases which do not occur naturally, that are generated by
human activity. Examples of these gases include; chlorofluorocarbons found in
refrigeration devices, hydrofluorocarbons, and perfluorocarbons. Each varies in their
heat trapping ability and combined with those gases originally present in the atmosphere;
serves to retain a sufficiently larger amount of heat then would naturally be retained.
.A major issue which is causing concern is that of our own health. Throughout the world,
the occurrence of particular diseases and other threats to human health depend largely on
the local climate. For example:
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extreme temperatures can directly cause the loss of life (although it has the
greatest toll on very old and very young people),
many severe diseases are only found in warm areas,
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and as well warmer temperatures have been shown to increase air and water
pollution.
On particularly hot days, more deaths seem to occur. In July of 1995, a heat wave killed
more than 700 people in the Chicago area alone.
Some possible reasons include:
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people who have heart problems must work harder to keep their body
temperatures down, it causes an increase in respiratory problems and exhaustion,
and also the high levels of ozone in the lower atmosphere acts as a pollutant,
causing damage to lung tissue, especially to people having asthma and other lung
diseases.
Increasing temperatures may also increase the risk of infectious diseases, which only
occur in warm areas, such as malaria, dengue fever, yellow fever, and encephalitis. These
diseases which are spread by mosquitoes and other insects could become more common
if warmer temperatures allowed these insects to inhabit places farther north.
Other impacts on the environment include areas such as:
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Water supply
Forests
Soil
There are many things that can be done to reduce global warming and insure the earth
stays inhabitable. What are some ways that we can help reduce the effects of global
warming? Discuss this with your classmates and make a list of actions that you can take.
Aquatic Eutrophication
If you look at a drop of pond water under a microscope you will discover an entire world
of very tiny organisms. Some are photosynthetic such as the microscopic algae, but many
are heterotrophic like the animals that live on land.
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. Oligotrophic lakes,
such as lake Michigan, are generally deep and contain cold water. The colder water
temperature has two advantages. Colder temperatures inhibit reproduction of the
microorganisms, and increases oxygen concentration since the colder the water
temperature the greater the quantity of oxygen gas that can be dissolved in it.
Enrichment, the fertilization of a body of water, 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.
Eutrophic lakes are generally shallower and warmer than oligotrophic lakes and because
there is a lower oxygen concentration in the water, they are unable to support the same
type of fish populations as found in oligotrophic lakes. Fish that tend to require relatively
high levels of dissolved oxygen, such as pike or trout, tend to die out and are replaced by
fish species, like catfish or carp, that can survive in lower levels of oxygen.
Years ago, phosphates were used in the manufacture of laundry detergents. Other sources
of phosphates and nitrates are untreated sewage from human and farm animal sources,
plant residues in waterways, and chemicals used in industrial processes. A ban on the use
of phosphates in the manufacture of laundry detergents, and better sewage treatment have
helped to solve the problem of accelerated aquatic eutrophication, but the problem has
not been completely solved.
According to the National Water Quality Inventory Report (1992), the main cause of
accelerated aquatic eutrophication is the contamination of freshwater systems by
fertilizers used in agriculture. As the human population expands, there is a greater need
for food resources. Fertilizers have enabled the same area of land to produce increased
crop yield but the same fertilizers are causing the acceleration of aquatic eutrophication
of our lakes and other freshwater systems.
Short Term Stress and Long Term Change
Every living organism has a range of tolerance within which it can survive. 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.
Short Term Stress:
Examples of short term stress include seasonal peaks in temperature, sudden changes in
water supply, or sudden but limited human impact.
Long Term Change:
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.
The Nature of Soil
As the world's population grows, there is an increasing demand for food and an increased
pressure on agricultural systems which includes soil use and management. Here we will
focus on the nature of soil (both abiotic and biotic). It will look at farming practice in
relation to soil as a sustainable resource.
Components of Soil:
Soil is a natural resource that is best considered as a non-renewable resource. The
physical and biological processes involved in the formation of soil take thousands of
years to complete. Most soil scientists describe soil as a series of layers, each having
different physical and chemical properties. In general the texture of the soil becomes
more coarse, and the amount of organic or living material becomes reduced with greater
depth.
The uppermost layer is known as topsoil and consists of fine textured mineral particles
(sand, clay, etc.) and organic material (decaying plant and animal material) known as
humus. This layer is important to life since this is the layer in which plants grow. The
topsoil is actually an ecosystem of microscopic and macroscopic organisms including
bacteria, fungi, protozoa, and several varieties of animals - nematodes, worms,
arthropods, etc. The interaction between the mineral components and the life forms that
exist in the soil make it possible to support the plants that normal associate with the soil,
and those animals that depend on the plants for their existence.
Below the topsoil is a layer known as the subsoil. In general the subsoil is more coarse
in texture and has less organic material. The number of organisms living in the subsoil is
generally reduced. Plant roots often invade the subsoil to gather water and mineral
resources stored in this layer.
Below these two layers is the bedrock, which is not considered a soil layer, but the
support for the soil layers above. The focus of this lesson will be on the nature of the
topsoil and subsoil and its management as a sustainable resource.
Factors which affect the ability of soil to support plant life are a major concern in both
forestry and agricultural industries. These factors include:
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soil fertility,
water storing capacity,
soil pH,
salinity,
and porosity to air (oxygen, nitrogen, and carbon dioxide).
Farming practice, including the use of fertilizers, pesticides, tilling and plowing of soil,
irrigation practice, and harvesting technologies all influence the soil as a living
community. One of the more important questions to consider is whether or not soil use in
forestry and agricultural industries can be maintained as a sustainable
Lab #2: Soil Nutrients and Plant GrowthComplete 3.5 "Investigation: Soil Nutrients and
Plant Growth " on pages 102 - 103. Complete all analysis questions a - j from within the
investigation and answer questions 1 - 2 from "Making Connections" on page 103.
Biomes and Biogeography
As one moves from the equator toward the poles of the Earth, the conditions of climate
gradually change and therefore the composition of the land and water. This change is
primarily a result of the change in the amount of solar energy that is able to penetrate to
the Earth's surface due to the change in latitude and the angle at which light strikes the
spherical Earth.
A biome is defined as a large geographical region that has a particular type of
climax community. A biome is therefore a distinct ecological community of plants
and animals living together in a particular climate. There are many different kinds of
plants and animals on the earth, but only certain kinds are naturally found at any
particular place. There are many different climates on the earth, and different plants and
animals have adapted to living in certain conditions. These conditions, such as the range
of temperature and rainfall that occur on average in a particular place, are called the
climate. Some places are hot, some are cold, some are wet and some are dry.
The biomes are generally distributed over the earth in horizontal bands that are linked to
climatic conditions associated with latitude and other geographical features such as the
proximity to large bodies of water or mountain ranges. The main factors that determine
biome distribution include latitude, altitude, soil, temperature, precipitation, and
light.
Terrestrial (land) biomes are defined by the dominant type of plant life (climax
community). The terrestrial biomes include the:
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Tropical Rain Forest,
Temperate Deciduous Forest,
Deserts,
Grasslands,
Taiga,
and Tundra.
There are also two types of aquatic biomes:
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the marine (saltwater or ocean) biome,
and the freshwater biomes (rivers, lakes, ponds, swamps, bogs, etc.).
Biomes of Canada:
Due to its latitude, Canada has four main terrestrial biomes which include the tundra,
taiga, temperate deciduous forest, and grassland biomes. These biomes also exist in
other parts of the Earth where environmental conditions are similar. The following map
indicates the distribution of the various biomes.
Pest Management
What is IPM?
IPM stands for Integrated Pest Management, a sustainable approach that combines the
use of prevention, avoidance, monitoring and suppression (PAMS) strategies in a way
that minimizes economic, health, and environmental risks.
Integrated pest management combines several approaches to the management of pests. In
this lesson you will explore two of these management control approaches - chemical
control, and biological control. Both control methods have been widely used in the
management of forests and agriculture.
Chemical control:
Chemical control makes use of chemical pesticides in the control of insect pests. Using
chemical control methods has several problems.
The first is the problem of biomagnification or bioamplification during which
concentrations of pesticides accumulate in higher concentrations at higher trophic levels
of the food web.
A second problem is that the use of chemical pesticides kills most but not all of the pest
population, leaving those pests which are resistant to reproduce a new population of
chemical resistant pests. This is an example of natural selection working on the pest
population resulting in pest infestation for which the chemical controls no longer work.
This problem is known as pesticide resistance.
A third problem is related to the lack of specificity which means that the chemical
pesticide tends to kill beneficial organisms as well as the pest organism targeted. This
upsets the natural balance in the food web due to the death of many natural predators.
Fenitrothion was once used in the Newfoundland forests but because it killed so many
beneficial organisms, its use was discontinued in 1989.
Biological Control:
Biological control makes use of natural predators, disease organisms, or competitors to
reduce the size of the pest population to a level that significantly reduces their impact on
the resource being protected. Gardeners use ladybird beetles (ladybugs), a natural
predator, to eat aphids which feed on garden plants.
Trichogramma minutum is a tiny parasitic wasp that has been used in forest management
of spruce budworm in Ontario. The female wasp parasitizes the eggs of the spruce
budworm. This has two advantages. It prevents the spruce budworm eggs from
developing into the larval stage. Since it is the larval stage of the spruce budworm that
eats the needles of the spruce trees, using the Trichogramma wasp prevents damage to
the needles of spruce trees and also reduces the size of the budworm population.
Winthemia occidentis is another example of the use of a parasitic organism. This tiny fly
lays its eggs on the pupa of the hemlock looper. Once the fly eggs hatch, they begin to
feed on the looper caterpillar. the looper caterpillar dies as a result, but the parasitic adult
fly soon emerges to infect other looper caterpillars.
A type of bacteria, known as B.t. (Bacillus thuringiensis), has been used in the
management of forest insects (mainly against spruce budworm and hemlock looper) in
Newfoundland. The bacteria are sprayed on the forest needles and picked up by the insect
pest. Once inside the digestive system of the insect, the bacterium acts like a disease
organism and kills the insect pest. One advantage of the use of B.t. is that it is generally
more specific than chemical pesticides, therefore causing much less upset to the natural
balance of the forest ecosystem.
There are at least three disadvantages to the use of B.t.
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First, the bacteria are washed off the needles of the tree by rain.
Secondly, they become less effective after a few days exposure to sunlight, so B.t.
only works for a short period of time.
Thirdly, the production of the bacteria tends to be expensive.
Pheromones are chemical "perfumes" produced by the female to attract a mate. The
female releases the pheromone into the air. The male detects the pheromone and follows
the scent to find the female.
Pheromones have also been used as a biological control technique both in forestry and
agriculture. Biochemists have isolated pheromone compounds and have been able to
manufacture them in the lab. The synthetic pheromones have been successfully used in
the biological control of some insect pests. One method of control involves using the
pheromone to attract insect pests to a trap. The trap contains a sticky glue which prevents
the escape of the insect.
Pheromone traps have also been used in the early detection of the pest in the forest
ecosystem. Early detection is important because the insect pest population is usually
much smaller in the early stages of a population outbreak, and a small outbreak of an
insect pest is far easier to manage.
It is also possible to use the pheromone to upset mating. This is accomplished by
spraying the synthetic pheromone within the forest ecosystem. The male insect detects
the pheromone from all directions so the male is unable to locate the female thereby
preventing mating.
It is the intention of integrated pest management (IMP) practice to combine both
chemical and biological approaches in such a way that the negative effects on human
health, economic cost, and environmental risk are minimized