Download Science 1206 - Unit 1 (Ecology)

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Science 1206
Unit 1: Sustainability of Ecosystems
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explain how a paradigm shift can change scientific world views in understanding
sustainability (114-1)
explore and develop a concept of sustainability in relation to a natural resource
industry (e.g., forestry, fishery, agriculture, aquiculture, mining, tourism, or
others)
define sustainability
examine historical attitudes and practices in relation to those of sustainability
communicate questions, ideas and intentions and receive, interpret, understand,
support and respond to the ideas of others with respect to environmental attitudes
(215-1)
discuss how attitudes towards our forests have changed with respect to (1)
commercial usage (2) residential usage (3) replanting programs
define a paradigm and paradigm shift
discuss how attitudes towards pesticides have changed
explain biotic and abiotic factors that keep natural populations in equilibrium and
relate this equilibrium to the resource limits of an ecosystem (318-5)
define ecology and ecosystem
explain how biotic and abiotic factors affect ecological interactions
define abiotic factors (include space, temperature, oxygen, light, water, inorganic
and organic soil nutrients)
define biotic factors (include decomposing animals, disease, predator/prey,
competition, symbiosis)
select, compile and display evidence and information from various sources, in
different formats, to support a given view in a presentation about ecosystem
change (214-3, 213-7)
define succession
describe the factors that contribute to succession
describe what is meant by the term climax community
examine the flow of energy in ecosystems using the concept of the pyramid of
energy
explain how energy availability affects the total mass of organisms in an
ecosystem and summarize this relationship in a pyramid of biomass
describe and apply classification systems and nomenclature with respect to
trophic levels in ecosystems (214-1)
define niche and relate it to habitat
classify organisms as producer, consumer, autotroph, heterotroph, decomposer,
herbivore, carnivore, omnivore, saprobe
define competition and explain how competition arises among organisms
differentiate between interspecific and intraspecific competition
describe the feeding relationships in terms of competition, food chains, and food
webs
explain how biodiversity of an ecosystem contributes to its sustainability (318-6)
demonstrate how the many interrelated food chains give a community stability
and identify the conditions required for a stable self sustaining ecosystem
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describe the mechanisms of bioaccumulation (or bioamplification) caused by
pesticide use, and explain its potential impact on the viability and diversity of
consumers at all trophic levels (318-2)
examine the use of pesticides over the course of human history
describe the impact that DDT usage has had on bird populations
describe how continued DDT usage in third world countries is impacting bird
populations.
Illustrate the cycling of matter through biotic and abiotic components of an
ecosystem by tracking carbon, nitrogen and oxygen (318-1).
33. Diagram the carbon cycle and describe the processes required to cycle from carbon
reservoirs to the atmosphere
34. Describe the importance of oxygen to ecosystems
35. Describe the significance of global warming and eutrophication
36. Plan changes to predict the effects of, and analyze the impact of external factors on an
ecosystem(331-6, 213-8, 212-4)
37. Describe how humans have altered the carbon, oxygen and nitrogen cycles in ecosystems
38. Describe what is being done to negate human impact on these cycles
39. Analyze the impact of external factors on the ecosystem biomes (331-6)
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weather change
introduced species
- pollution
industry/agriculture
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Explain why the ecosystem may respond differently to short-term stress and long
term change.
41. Describe the potential impact that a large scale logging project could have on a native
species such as the pine martin
42. Explain the impact that an abnormally dry summer could have on a bog ecosystem.
43. Describe how ecosystems are able to respond to changes and return to its previous state
44. Communicate questions, ideas and intentions, and receive, interpret, understand, support
and respond to the ideas of others in preparing a report about ecosystem change
45. Describe how soil composition and fertility can be altered and how these changes could
affect an ecosystem. (331-7)
46. Explain the role that fertilizers and irrigation practices have had on soil quality
47. Describe the potential impact that overuse of fertilizers can have on ecosystems
48. Explain why ecosystems with similar characteristic can exist in different geographical
locations (318-3)
49. Relate the distribution of biomes within Canada to the impact of external factors
50. Discuss how abiotic factors affect the distribution of organisms
51. Discuss the reasons for ecosystems that share similar abiotic features also sharing similar
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animal life
Describe how Canadian research projects in environmental science and technology are
funded (117-3)
Compare the risks and benefits to the biosphere of applying new scientific knowledge
and technology to industrial processes(118-1)
Propose and defend a course of action on a multi-perspective social issue (118-9, 215-4,
118-5)
Describe the role peer review has in the development of scientific knowledge (114-5)
Identify examples where scientific understanding about an ecosystem was enhanced or
revised as a result of human invention or related technologies (116-1).
Discuss the improvements that have occurred with respect to pest control
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Topic 1: Sustainability and Changing Paradigms
The way that humans view the world is known as a paradigm.
Old paradigms have been replaced by new paradigms.
Changes in paradigms are known as paradigm shifts.
The paradigms of modern man differ from the paradigms of our forefathers.
The modern paradigm views the Earth as a sustainable system provided that renewable
resources are not used at a faster rate than they are replaced or recycled.
From this vantage point it is easy to recognize that the earth is for the most part, a closed
system. The materials that make up the biosphere are not limitless as was once believed.
These materials are recycled
The term sustainability means that the system can meet the needs not only of our present
human population, but also those of the future.
Changes in our paradigms about our forests:
If trees were cut down to build a ship, a home, or to use as fuel, little or no
thought was given to it. The forests extended as far as the eye could see, and beyond. The
forest would simply grow new trees to replace those taken. People would never have to
worry about having enough trees for their use. The early foresters used simple tools
including an axe and a saw. A typical forest worker could cut and stack about two cords
of wood per day. Today, technology has changed and the equipment is available which
can cut 2 cords of wood in just a few minutes rather than a day. With this change in
technology, can our forests now be considered limitless? What will happen to our forests
if we cut them down at a rate faster than they can grow back? What effect does clearcutting have on the forest ecosystem?
Changes in our paradigms about our fishery:
Fish would be taken from the seas with no thought about the number that remained. It
was believed that man could never take all the fish that existed within the lakes and
oceans because there were so many fish and relatively so few fisherman. The technology
used by the inshore fisherman included the use of an open boat known as a dory and a
single jigger (large hook with an attached lead weight fashioned like a fish) attached to a
length of line. The jigger was thrown over the side of the boat and allowed to sink to the
bottom. The jigger would then be brought up just off the bottom and jigged up and down
until it struck a cod. The cod was then hauled to the surface and thrown into the boat at
the fisherman's feet. This cycle was repeated until the boat was full.
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Modern technology has changed to include the use of factory ships which make use of
drift nets more than 5 km long, and electronic equipment designed to detect the location
of the fish. As a result of modern technology, fish are caught by the metric ton rather than
as individual fish. The number of fish taken as a result of the use of modern technology
has destroyed the fish stocks to the point that the Atlantic Canada fishery has been shut
down to allow the recovery of the fish stocks. Was the change in fishing technology
sustainable? Can we manage a sustainable fishery in the future?
Introduction to Ecology
Ecology is the scientific study of the interactions of organisms and their environment. As
a scientific study, ecology involves observations and experiments to test hypothetical
explanations of ecological phenomena.
Ecology is a multidisciplinary field of study involving all areas of biology as well as the
physical sciences. Interactions of organisms and their environment refers to the way the
organism affects the environment as well as how the environment affects the organism.
An Ecosystem is a community of organisms and the physical environment in which it
lives. When an ecologist studies the organisms living in a forest and includes a study of
the physical factors that affect the organisms in the forest, then the ecologist is studying
an ecosystem.
Abiotic factors are the nonliving factors which affect life in any ecosystem. Some abiotic
factors are described below:
1. Space - All organisms require enough space or territory to insure adequate
resources to food, water, shelter, and mates.
2. Temperature - Environmental temperature affects biological processes and the
ability of most organisms to regulate their temperature. Few organisms have
active metabolisms at temperatures below 0oC or above 45oC because enzymes
function best within a short range of temperature and become denatured if the
temperature is too high. Most organisms are ectotherms and can maintain their
body temperature only within a few degrees of ambient temperature. Even
endotherms function best in a temperature range for which they are adapted.
3. Oxygen - Most living organisms require oxygen for cellular respiration, which is
a process that releases energy from food. Terrestrial organisms obtain oxygen
from the atmosphere as they breath (usually with lungs). Aquatic organisms
generally have gills and extract oxygen which is dissolved in the water.
4. Sunlight - Sunlight is the ultimate source of energy for all photosynthetic
organisms which in turn provide the resources for other living things (in most
ecosystems).Light also affects the development and behavior of many organisms
which are sensitive to photoperiod.
5. Water - Water (humidity) is necessary for all life. The ability to find water, to
maintain water balance, and to conserve water help determine the habitat range
for each species.
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6. Inorganic and Organic Soil Nutrients - Inorganic soil nutrients include minerals
such as phosphates, nitrates, potassium, magnesium and a host of other minerals
derived from rocks. Organic nutrients include organic compounds in humus
which promote the growth of bacteria, fungi, and a host of other organisms
beneficial to the soil.
Biotic factors refer to the living environment and include all other organisms that
interact with the individual both of the same species and all other species.
Biotic factors also includes decomposing animals and plants (detritus), disease,
predator/prey interactions, competition, and symbiotic relationships (symbiosis).
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Detritus refers to decomposing plant and animal materials including their dead
bodies as well as their wastes. Bacteria and fungi living in the ecosystem help to
break down the materials within the detritus and recycle these materials back to
the plants.
Disease is the result if infection by fungi, bacteria, virus, and other pathogens.
Disease is an important biotic factor because disease tends to reduce the number
of organisms within the community.
Predator/prey interaction is another important biotic factor which helps to limit
the size of populations within an ecosystem. A predator is an animal that kills and
eats another animal for food. The prey is the hunted animal. There is a balance
between the number of predator and prey in any ecosystem.
Competition is a struggle for survival that occurs between two organisms either
of the same or different species. Birds often compete for nesting space
Competition tends to limit the size of the population keeping it in balance with the
available resources.
Symbiotic relationships are biotic relationships in which two different organisms live in
close association with each other to the benefit of at least one. There are five types of
symbiotic relationships including: mutualism, commensalism, parasitism, parisitoidism.
and predation.
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Mutualism is the type of symbiosis resulting in mutual benefit to both of the
organisms in the relationship.
An example of this would be the relationship between the algae and
fungus of lichens. The fungi penetrate the roots of the plants and make soil
nitrogen available to the plant, receiving carbohydrates in return. This
allows them to live in an environment in which neither could survive
alone.
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Commensalism is a relationship in which one organism benefits from the
relationship but the other organism seems to neither be harmed nor benefited.
One example to illustrate commensalism is the beaver and the fish. A
beaver builds a dam to regulate water level which helps the beaver survive
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winter. Fish often inhabit the beaver pond. The fish benefit from the
beaver, but the beaver is neither harmed nor gains benefit from the fish
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Parasitism is a symbiotic relationship in which one organism benefits and the
other is harmed. The organism that benefits is called the parasite, the organism
that is harmed is called the host. Some parasites only cause slight damage to their
host, while others kill them. Therefore one organism is injured in satisfying the
needs of the other.
An example would be the tapeworm. they live in the digestive tracts of
various organisms, while there they are provided with nutrient and an
environment in which to grow and reproduce. However, the host is
harmed by the presence of the tapeworm.
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Parisitoidism is similar to parasitism. One organism benefits but the other is
eventually killed - a sort of slow death.
An example of parisitoidism is when a female wasp stings a spider
causing paralysis but not death. The wasp then lays a single egg on the
spider. When the egg hatches into a larva, it slowly eats the body of the
spider eventually killing it - but slowly.
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Predation is where the interaction is beneficial to one species and detrimental to
the other. This is not always considered a symbiotic relationship, although it is quite
similar to parasitism, except for the degree of harm to the host or prey. With predation,
the prey is killed.
An example of predation is when a lion kills a zebra and eats it as its source of food.
Trophic Structure:
Trophic structure refers to the feeding relationships within the ecosystem. These
feeding relationships are generally divided into five trophic levels based on their source
of nutrition
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Primary producers
Primary consumers
Secondary consumers
Tertiary consumers
Decomposers
The various organisms that comprise each of the trophic levels determines the flow of
energy and the cycling of materials within the ecosystem.
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Feeding relationships are generally viewed as a food web consisting of all the possible
food chains that exist within the ecosystem.
Producers or autotrophs are organisms, such as green plants, that produce their own
food. They make organic compounds (food such as sugar) from inorganic compounds
(carbon dioxide and water) by photosynthesis.
The ultimate source of energy for life on Earth is the sun. Solar energy is trapped
during the process of photosynthesis and converted into a chemical form that we
normally call food. The materials within the food are recycled. They pass from
the producers to the consumers and finally are recycled back to the producers by
the action of the decomposers.
Consumers or heterotrophs are organisms that obtain nutrients from other organisms.
They cannot synthesize their own food so they must obtain it ready made. They eat other
living things.
There are many levels of consumers. A mouse is considered a primary consumer (or
first order consumer) because it feeds directly on a plant. A primary or first order
consumer is also called an herbivore.
A snake is considered a secondary consumer (or second order consumer) and is called
a carnivore.
A hawk that feeds on the snake is an example of a tertiary consumer (or third order
consumer). The hawk is also considered a top carnivore since there are no carnivores
that feed on it. The hawk is considered to be at the top of the food chain.
Decomposers are organisms of decay. These are also called saprobes. They are
generally fungi or bacteria that break down the complex compounds in the remains of
dead animals and plants, producing simple substances that can be used again by the
producers. Decomposers are therefore very important because they recycle materials
within the ecosystem. The decomposers are the final consumers in any ecosystem.
Herbivores, Carnivores, Omnivores, and Saprobes:
-There are several groups of heterotrophs.
-Heterotrophs are all organisms that obtain their food from the environment.
-All animals and certain types of micro-organisms are heterotrophs.
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Herbivores are animals that feed only on plants. Rabbits, cattle, horses, sheep and
deer are all herbivores.
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Carnivores are animals that feed on other animals. Some carnivores may be
predators (such as lions, hawks, and wolves who attack and kill their prey and
feed on their bodies) and some may be scavengers (they feed on dead animals that
they find).
Omnivores are animals that feed on both plants and animals. Examples of
omnivores are humans and bears.
Saprobes are organisms that get nutrients by breaking down the remains of dead
plants and animals, or their wastes. Examples of saprobes are bacteria and fungi.
Saprobes are also known as decomposers are an essential component of any
ecosystem. Their main role is to recycle nutrients in dead organisms and their
wastes. Without the decomposers to recycle nutrients, there could be no life since
plants would run out of nutrients.
Energy flow through an ecosystem
The vast majority of life on Earth depends on sunlight as its source of energy. Of all the
radiant energy that reaches the earth, some of it penetrates the earth's atmosphere to the
Earth's surface, but only a small quantity is used to drive the process of photosynthesis.
Albedo Effect:
The actual amount of energy that reaches the surface of the Earth is affected by the
albedo effect of clouds and dust particles in the atmosphere. Albedo is a measure of the
amount of light reflected from an object. Albedo is normally expressed as a decimal
value representing the percentage of light reflected.
Photosynthesis, a biological process, uses the energy of sunlight to manufacture sugar,
which serves as the universal food for life. Oxygen produced as a product of
photosynthesis is released into the environment.
The formula for this reaction is:
6CO2 + 6H2O + sunlight energy → C6H12O6 + 6O2
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where CO2 represents carbon dioxide
H2O represents water
C6H12O6 represents the sugar molecules (carbohydrate)
and O2 represents oxygen
As you can see from the formula, the energy that had originally come from the sunlight is
transferred to the molecules of sugar, (C6H12O6 ), as indicated in the equation above. The
sugar serves as the source of energy for nearly all life on Earth. The energy stored in the
sugar is passed from the plants to other organisms when the plants are consumed as food.
This passage of food from producer to various consumers in turn is known as a food
chain.
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If the community has a great deal of biodiversity, there will be several organisms that can
feed on more than one type of food resource, and as a result there would be several
possible food chains. All of the possible food chains together make up a food web. Each
step in the food chain is called a trophic level. Consider the following simple food chain
with four trophic levels:
Corn → Mouse → Snake → Hawk
Notice that the pathway of energy flow in the food chain/web always begins with a
producer. Producers are also known as autotrophs because they make their own food.
The mouse, snake, and hawk are consumers. Consumers are called heterotrophs because
they can not make their own food. Heterotrophs must obtain their nutrients from the
organisms they eat.
Although the hawk is the top carnivore in this example, it is not actually the final
consumer. Consider what happens when the hawk or any other member of the food chain
dies! The final consumers in any food chain/web are the decomposers. Decomposers are
organisms of decay, that make use of wastes and remains of dead organisms.
Corn → Mouse → Snake → Hawk → Decomposers
To release the energy stored in the sugar, organisms carry out a metabolic process known
as cellular respiration. The energy released during cellular respiration is what enables
organisms to carry on their life processes such as movement, growth, and reproduction.
The process of cellular respiration does transfer energy from the food to the organism for
carrying life processes, but also releases heat which cannot be used any further. Heat
energy is lost on a continuous basis from all living things.
The transfer of energy from one trophic level to the next is never 100% efficient since
each organism must utilize some of the energy to support its own existence.
The idea that each higher trophic level has less energy available to it is known as the
pyramid of energy.
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The Pyramid of Energy.
Energy, unlike the materials, is not recycled. As the food is passed through the food web,
most of the energy is lost. In general terms, about 10% of the energy stored in one trophic
level (such as producers) is actually transferred to the next trophic level (for example the
herbivores) Eventually there is so little energy remaining in the top trophic level that no
higher trophic level can be supported. This is why there are so few if any fourth order
consumers in an ecosystem.
The figure below represents the 10% rule for energy transfer.
Pyramids of Biomass and Number
Since the amount of water present within the tissues of different organisms varies,
biologists use the dry mass of the organism for comparison since it is believed that dry
mass more closely reflects the actual amount of "living matter" in the organism.
The dry mass is known as biomass. The availability of energy will also affect the number
of organisms and the mass of the organisms at each trophic level.
The pyramid of biomass is a graphical representation of the total biomass of all the
members of each trophic level. Generally the pyramid of biomass has the same shape as
the pyramid of energy.
In a grassland environment, 10,000 kg of grass and other producers (dry mass) should
support about 1,000 kg (dry mass) of grasshopper and other plant eating insects.
The pyramid of numbers
The pyramid of number is the third type of graphical representation used by biologists
to study ecosystems. The pyramid of number is often similar in shape to the pyramid of
energy or biomass, but there are exceptions.
Consider a single spruce tree in a boreal forest (biomass = 100 kg) which is infested by
100,000 spruce bud worms (total biomass = 10 kg), which are in turn eaten by 5 insect
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eating birds (total biomass = 1 kg). The pyramid of biomass would appear normal (base
representing 100 kg, middle piece representing 10 kg, and a top piece representing 1 kg).
The pyramid of number for this example will not look normal. The pyramid of number
would have a very small base representing the producer (1 tree), a very large herbivore
level (100,000 spruce bud worms), followed on top by a small predator level (5 birds).
Tying it all together
Stability means that there is an ecological balance between the various organisms that
make up the food web, and because of this balance the ecosystem is self-sustaining over
long periods of time. To be stable there must be a balance between food production, food
consumption, and decomposition of dead organisms and/or their wastes.
This means that a stable ecosystem must have a source of energy (usually sunlight for
photosynthesis), producers to capture the sunlight and make food, and a means to recycle
the materials. The greater the biodiversity in the ecosystem the more stable it will be.
Biologists have also recognized that some species in the ecosystem function as a
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.
Succession (pg. 48-49)
Ecological succession refers to the series of ecological changes that every community
undergoes over long periods of time.
The process of succession begins with relatively few pioneering plants and the animals
that are associated with these plants. The plant life serves as food, and often shelter for
the animal life that can survive in that environment. The succession in the plant life is
therefore paralleled by a succession in animal life. As a result of the process of
succession, a primitive community develops.
The organisms that make up the primitive community gradually change the
environmental conditions so each successive community paves the way for the next.
Each successive community develops through increasing complexity until it becomes a
final, sustainable, stable, or self-perpetuating community, of dominant organisms, known
as a climax community.
The climax community is the final stage of ecological succession.
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Primary Succession
Secondary Succession
Contributing Factors
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Primary succession:
There are two types of succession, the first type of succession is called primary
succession which refers to a sequence beginning in an area where there is no soil or
previous forms of life. Primary succession occurs in an area such as a freshly cooled lava
field, or a newly formed sand dune. In terrestrial habitats, primary succession is a very
slow process because it begins with the formation of soil. The soil forms as a result of
weathering and the action of pioneer organisms. Large rocks are broken down into
smaller pieces and eventually bacteria, fungi, and lichens inhabit the area. These
organisms are known as pioneer organisms because they are the first type of life to
inhabit the region.
The pioneer organisms add organic matter to the primitive soil, changing the conditions
of the microenvironment so that mosses, ferns, and other primitive plants begin to take
over. Grasses may eventually replace the more primitive plants and when they die, they
make the soil even richer. Shrubs grow and shade the grass causing it to die. Then trees
may grow and shade out the shrubs. Seedlings of other trees may grow well in the shade.
In this way, one community of trees will be succeeded by another community with
different trees.
Secondary Succession:
Secondary succession occurs in an area in which an existing community has been
partially destroyed and its balance upset, either by natural causes, such as fire, or as a
result of human activity, such as the cutting of a forest, or abandoning a farm.
The major difference between primary and secondary succession in a terrestrial
environment is that in secondary succession, soil already exists.
Factors that contribute to ecological succession:
The type of climax community that is established will depending on the environmental
conditions of the area. The most important environmental conditions that affect
succession include:
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climate (temperature, precipitation, and availability of sunlight),
soil (salinity, fertility, moisture, texture, etc.),
and geographical features (latitude, altitude, and proximity to mountain ranges or
large bodies of water).
For example, in a hot arid desert, the climax community will certainly be quite different
from the climax community that would form in a humid but cool environment such as a
boreal forest (Taiga).
Some biologists argue that there is no such thing as a climax community because the
entire earth is in constant change or upset. The causes of upset include:
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natural (catastrophic events such as flood, fire, volcanic activity, climate change,
species extinction, etc.),
and human influenced (such as acid rain, ozone depletion, enhanced global
warming, pollution, habitat destruction, monoculture farming, clear-cut logging,
over-fishing, etc.).
Niche, Habitat, and Competition
Niche, refers to the role that a species plays within its ecosystem. In balanced
ecosystems, each species occupies its own niche. The niche is like the organism's
profession - what it does to survive.
Habitat refers to the place were an organism lives. The habitat of a species is different
than its niche, it is the particular part of the environment in which it lives. The habitat of
an organism is part of its niche. The organism's habitat is its address - where it lives.
Every organism has its own habitat. The organism's habitat is where the organism is best
adapted to survive.
Plants and animals live where they can gather or find the necessary resources to satisfy
their needs. Every habitat includes factors that limit the kinds and numbers of organisms
that live there. Goldfish and pond plants require fresh water. On the other hand, the
barnacles that cling to the ship must live in salt water. In some cases, creatures can adapt
themselves to a changing habitat.
A single area may satisfy the needs of many kinds of plants and animals. These
organisms that associate together in a common habitat form communities.
Competition
Competition between organisms exists in every ecosystem. Organisms are forced to
compete against their own species and also different species in order to survive. The
stronger and fit organisms have an advantage over those who are weaker, and they have a
better chance of surviving.
Competition arises when organisms have requirements in common and they must
compete to meet their own needs. The more needs organisms have in common, the more
intense the competition. When the resources that are being competed for become scarce
the competition becomes more intense, and eventually one of the species becomes
eliminated.
Competition between the same species is called intraspecific competition. Many birds
of the same species compete for the best nesting grounds. In cases when food or water is
scarce, members of the same species will compete for food in order to survive.
Competition between different species is called interspecific competition. Different
species often compete for space, food, or water. For example the lion and the hyena both
compete for zebra. The majority of feeding relationships in an ecosystem are based on
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competition, food chains and food webs. Each species has it's own niche, that species has
a particular habitat and has a particular way of obtaining its own food. But when two
different species overlap or interfere with one another, competition occurs. When worst
comes to worst, those with the most helpful adaptations will survive and the less-well
adapted will not.
Canada’s endangered species.
Classifying species at risk.
Many animals in Canada for one reason or another are considered at risk. The system of
classification is as follows:
Wildlife Species A species, subspecies, variety, or geographically or genetically distinct
population of animal, plant or other organism, other than a bacterium or virus, that is wild
by nature and it is either native to Canada or has extended its range into Canada without
human intervention and has been present in Canada for at least 50 years.
Extinct (X) A wildlife species that no longer exists.
Extirpated (XT) A wildlife species no longer existing in the wild in Canada, but
occurring
elsewhere.
Endangered (E) A wildlife species facing imminent extirpation or extinction.
Threatened (T) A wildlife species likely to become endangered if limiting factors are not
reversed.
Special Concern (SC) * A wildlife species that may become a threatened or an
endangered wildlife species because of a combination of biological characteristics and
identified threats.
Not at Risk (NAR) ** A wildlife species that has been evaluated and found to be not at
risk of extinction given the current circumstances.
Biogeochemical Cycles
Biochemists are scientists who study the type of chemical compounds that are found in
living things. They study the interaction of these compounds in an attempt to understand
how life works at the chemical level. The work of biochemists has lead to the realization
that living organisms are composed of some of the same elements that are found in the
air, water and soil. Following many years of analysis on many different organisms,
biochemists have been able to describe the types of elements found in plant and animal
tissues.
Although each organism is different in terms of the relative amounts of each type of
element, the types of elements present are the same. Although there are 92 elements
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know to occur naturally on Earth, fewer than 20 elements are presently known to occur in
the tissues of living things. Only 6 elements make up 99.2% (rounded to 3 significant
digits) of human or pumpkin tissues. The table below compares the relative abundance
(percentage by weight) of a few selected elements found in the Earth's crust, human, and
pumpkin.
Element Name
Earth
Human
Pumpkin
(Symbol)
% weight
% weight
% weight
Oxygen (O)
46.6
65
85
Carbon (C)
0.19
18
3.3
Hydrogen (H)
trace
10
10.7
Nitrogen (N)
trace
3
0.16
Calcium (Ca)
3.6
2.0
0.02
Phosphorus (P)
trace
1.2
0.05
Potassium (K)
2.6
0.20
0.34
trace
0.25
<0.05
Sodium (Na)
2.8
0.1
0.001
Magnesium (Mg)
2.1
0.05
0.01
trace
0.15
<0.05
5.0
trace
0.008
Copper (Cu)
trace
trace
0.0001
Iodine (I)
trace
trace
<0.05
Silicon (Si)
27.7
trace
trace
Zinc (Zn)
trace
trace
0.0002
8.1
trace
trace
trace
trace
trace
Sulfur (S)
Chlorine (Cl)
Iron (Fe)
Aluminum (Al)
others
As you can see from the table, oxygen, carbon, hydrogen and nitrogen make up the vast
majority of living tissue. These four elements are recycled between living organisms and
the soil, water and atmosphere of the Earth.
These elements are first taken up by plants, some oxygen is released to the atmosphere as
a product of photosynthesis, but the rest is converted into food, passed through the food
web as they pass through plants, consumers, and finally decomposers such as fungi and
bacteria, and then returned to the environment in a continuous recycling of materials. If
recycling of these materials did not occur, life could not exist.
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The continuation of life depends on the continued recycling of the materials that make up
the food that passed through the ecosystem. Some of these elements (carbon, oxygen,
sulfur, nitrogen) are found in gaseous forms and their cycles involve the atmosphere. As a
result they have a global nature. One should also be aware that some of the elements may
have a short term cycle such as when carbon is transferred from animals to plants in the
form of carbon dioxide and a long term cycle such as the transfer of carbon from a fossil
fuel to a plant following combustion.
The elements are cycled between the living organisms and the environment (both long
and short term). It is a combination of biological and geological processes that drives
chemical recycling.
Biological processes include:
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respiration,
decomposition,
excretion,
photosynthesis,
and assimilation.
Geological processes involve fossilization, erosion, combustion of fossil fuels (peat, oil,
coal), weathering, and formation of sedimentary rock.
Carbon Cycle
Plants extract carbon dioxide and water from their environment. They use the energy they
capture from the sun to carry on a process known as photosynthesis which converts the
atoms in the carbon dioxide and water into sugar and oxygen.
6CO2 + 6H2O + energy → C6H12O6 + 6O2
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The oxygen, released as a byproduct of photosynthesis, generally passes into the
atmosphere. The sugar (known as glucose) serves a food for all consumers in the
ecosystem. The consumers carry on a metabolic process known as cellular respiration.
During cellular respiration, oxygen is taken in from the atmosphere and used to break
down the sugar resulting in a release of energy and the molecular products, carbon
dioxide and water.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
What do you notice about these two reactions?
As you can see from the equations, photosynthesis and cellular respiration are
complementary processes. Provided these processes occur in balance, the amount of
carbon dioxide (about 0.023% of the air) and oxygen (about 21% of the air) are
maintained in equilibrium. This balance is called the carbon-hydrogen-oxygen cycle (or
simply carbon cycle for short).
In modern times (past 200 years) people have discovered these fossil fuel deposits and
have used them to supply our energy needs. Humans have also affected the carbon cycle
by cutting down forests. As a result of human activity, the amount of carbon dioxide is
being produced at a faster rate than nature can recycle it. As a result of this imbalance,
the amount of carbon dioxide in the atmosphere is increasing. As a result the earth is
presently undergoing an enhanced greenhouse effect in which the atmosphere is
gradually heating up. The gradual rise in temperature is predicted to have a disastrous
effect on world biomes. If the rise in temperature occurs too fast for organisms to adapt,
widespread extinction of plants and animals may be the result. Extinction events have
occurred in past history, but never the result of human influence. We are the only species
that can do something about the problems we have created.
The Nitrogen Cycle
Nitrogen is essential to living things for the production of amino acids used to synthesize
proteins, and nucleic acids which are used to carry the hereditary or genetic code. Life
can not occur without these compounds. Even though the atmosphere is about 78%
nitrogen gas, plants and animals are unable to use nitrogen gas directly as a source of
nitrogen to make organic nitrogen compounds. The nitrogen cycle can occur in both
terrestrial and aquatic ecosystems but this lesson will focus on the nitrogen cycle of
terrestrial ecosystems. The nitrogen cycle is an extremely complex cycle involving many
species of bacteria. The nitrogen cycle however can be simplified into 5 steps described
below.
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1.Nitrogen Fixation
• Lightning can fix nitrogen:
The electrical energy from the lightening cause nitrogen gas (N2) to react
with Oxygen in the atmosphere to produce nitrate ions (NO3-) which
reaches the soil dissolved in precipitation.
• Done primarily by bacteria:
Bacteria in the soil can change Nitrogen gas into ammonia (NH3) which then
dissolves in water to form ammonium ions(NH4+)
2.Nitrification
Involves the oxidation of nitrogen by specialized bacteria:
It is a bacterial process in which ammonium ions are converted into nitrate ions.
They are first changed into nitrites (NO2-) by bacteria, and then converted to
Nitrates (NO3-) by a different group of bacteria.
3. Assimilation: The making of proteins for consumer use.
Assimilation is the process by which plants use the nitrate ions (NO3-) to
make amino acids, proteins, and DNA. Only plants and bacteria can carry out
the process, all other living organisms receive their nitrogen compounds from
the food they eat.
4. Ammonification
Process by which bacteria and some fungi break down these nitrogen
compounds to make ammonia. The ammonia immediately dissolves in soil
water to form ammonium ions. (NH4+)
5.Denitrification:
During this step, nitrites are changes to Nitrogen gas which returns to the
atmosphere. It is basically the reverse of nitrogen fixation and nitrification.
NO3- → NO2- → NO
NO → N2O → N2
Done by bacteria!
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
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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.
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.
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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,
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:


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
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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
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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.
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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
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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:


the marine (saltwater or ocean) biome,
and the freshwater biomes (rivers, lakes, ponds, swamps, bogs, etc.).
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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.
Pests and Pesticides
What are pests?
Pests are living organisms that are not wanted around us. Examples of pests include
unwanted dandelions growing in the lawn; rodents or insects that eat fruits, vegetables or
other crop species; micro-organisms that cause disease in forest, fish, or crop resources,
etc. A pest is any organism that man believes is undesirable, has a negative impact on the
human environment, or is in competition with human use of a resource, either natural, or
cultivated.
Early Pesticide Use:
Early pesticides included the use of toxic inorganic metallic salts such as copper sulfate,
lead salts, arsenic, or mercury. These substances were generally effective against the
intended pest, but also created some environmental problems because they also killed
other beneficial organisms, and polluted water and soil resources used by man. Most
early pesticides were non-biodegradable (meaning that they were not broken down within
the ecosystem). As a result, these early pesticides began to accumulate in the
environment, contaminating water and soil resources, eventually poisoning humans.
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Modern Pesticides:
By the twentieth century, chemists began to develop organic pesticides that were
designed to be less toxic to man and more specific toward the intended pests. Although
this was initially believed to be a step in the right direction, man soon discovered that the
organic pesticides also caused unexpected environmental effects. Some of these
pesticides were fat-soluble. This characteristic leads to a problem known as
bioaccumulation.
As each organism feeds on one lower in the food chain, the fat-soluble pesticide began to
be concentrated in ever higher amounts as one moved toward the top of the food pyramid.
Since every organism eats far more than its own body mass in food, the tiny amounts
found in each organism in the lower levels of the food web began to accumulate in
greater concentrations in species located at higher trophic levels.
One example of this problem is illustrated by the damage done to predatory birds as a
result of bioaccumulation of DDT. As a result of this problem DDT has been banned
from use in North America.
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.
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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
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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
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