Ecology

Unit Notes

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Ecology- Unit Outcomes -

S2-1-01 Illustrate and explain how carbon, nitrogen, and oxygen are

cycled through an ecosystem.

S2-1-02 Discuss factors that may disturb biogeochemical cycles. Include: natural events, human activities.

S2-1-03 Describe bioaccumulation and explain its potential impact on

consumers. Examples: bioaccumulations of DDT, lead, dioxins, PCBs, mercury...

S2-1-04 Describe the carrying capacity of an ecosystem.

S2-1-05 Investigate and discuss various limiting factors that influence

population dynamics. Include: density-dependent and densityindependent factors.

S2-1-06 Construct and interpret graphs of population dynamics.

S2-1-07 Describe potential consequences of introducing new species

and species extinction on an ecosystem.

S2-1-08 Observe and document a range of organisms that illustrate

the biodiversity within a local or regional ecosystem.

S2-1-09 Explain how the biodiversity of an ecosystem contributes to

its sustainability.

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S2-1-10 Investigate how human activities affect an ecosystem and

use the decision-making process to propose a course of action to enhance its sustainability. Include: impact on biogeochemical cycling, population dynamics, and biodiversity.

Introduction to Dynamics of Ecosystems Have you ever wondered where the substances from which you and other living things are made come from?

Why do they not run out?

Where do the chemicals go that we spray on the ground or plants to control pests?

When you observe an ecosystem, we see many different organisms. The population of a given type of organism, like a rabbit, seems to remain fairly constant. Many other creatures eat rabbits. Why do the rabbits not disappear?

What happens if a new creature that eats rabbits appears in an ecosystem?

Humans interact with ecosystems. Humans need food, water, energy and shelter. The resources for these are found in the ecosystems in which humans live. What kind of effect do human beings have on ecosystems?

How can humans use the resources but still allow the ecosystem to sustain itself and humans for the centuries to come?

Who makes the decisions about how resources should be used?

How are these decisions made?

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Do you have a role in this process?

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Dynamics of Ecosystems Concept Map

The following CONCEPT MAP outlines the concepts that you will be studying in this unit. The concept map is provided as an outline to illustrate how these ideas fit together, that is, the big picture into which all the details will fit.

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Interactions Among Living Things

ECOLOGY is the branch of biology that deals with the study of the INTERACTIONS AMONG ORGANISMS AND THEIR ENVIRONMENT.

The prefix “ECO” comes from the Greek word “OIKOS” which means HOUSE.

Scientists who study ECOLOGY are called ECOLOGISTS.

Because our planet has many diverse plants, animals and environments, ECOLOGISTS tend to study SMALLER AREAS called ECOSYSTEMS.

An ecosystem consists of the 1. The PHYSICAL ENVIRONMENT or ABIOTIC factors.

2. The LIVING THINGS or BIOTIC factors within it

At first glance an ecosystem may appear simple, even boring. Upon closer examination, you will notice the wide variety of living things present in the ecosystem.

Examples of ABIOTIC factors in the physical environment include:

WATER SUNLIGHT OXYGEN

SOIL NUTRIENTS TEMPERATURE

Examples of BIOTIC factors in an ecosystem include: PLANTS ANIMALS

FUNGI BACTERIA

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Case study: Comparing Ecosystems (Pg. 29)

Habitat vs. Niche

Each type of LIVING thing in an ecosystem has a PLACE in which it LIVES. This is known as its HABITAT.

The FUNCTION or JOB an organism performs in its habitat is called its NICHE.

What are some NICHES (jobs) that organisms have? Plants and algae trap the energy in sunlight and produce

their own food. PRODUCERS. Animals are CONSUMERS since they cannot make their

own food and must obtain their food from producers. Bacteria and fungi are DECOMPOSERS. They eat dead

plant and animal remains and convert them into substances that can be reused. They are the RECYCLERS of the ecosystem.

Energy Flow

All organisms need ENERGY to carry out the activities of life such as:

MOVING FEEDING

REPRODUCING GROWING

Only PLANTS are able to take ENERGY FROM THE SUN and use it to drive their activities (PRODUCERS).

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Most organisms cannot take the energy from the sun and use it directly for their own purposes. Instead, they EAT OTHER ORGANISMS to obtain their energy (CONSUMERS).

Since organisms only eat certain other types of organisms, the trail of the ENERGY can be traced as it flows along from organism to organism – this can be shown through a FOOD CHAIN

Food Chains

Let’s take a closer look at the interactions between organisms in an ecosystem.

Since all living things require energy to live, the ULTIMATE SOURCE of that ENERGY is the SUN.

Producers such as PLANTS and ALGAE capture the sun’s energy and transform it into ORGANIC COMPOUNDS

These COMPOUNDS are used to BUILD plant parts such as LEAVES and FLOWERS, or store EXTRA ENERGY in ROOTS and SEEDS.

Unlike producers, CONSUMERS are unable to directly transform sunlight into organic compounds.

PRIMARY (1o) consumers (also called HERBIVORES) feed directly on plants. o Examples of herbivores include MOOSE, CATTLE,

GRASSHOPPERS, RABBITS and APHIDS.

SECONDARY (20) consumers feed on primary consumers, and TERTIARY (3o) consumers feed on secondary consumers.

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o These higher-level consumers (20 & 3o) are also known as CARNIVORES

o Examples of carnivores include WOLVES, NORTHERN PIKE, EAGLES, POLAR BEARS, LADYBUGS and SNAPPING TURTLES.

SCAVENGERS are CARNIVORES that feed on DEAD animalso Examples of scavengers include BLOWFLIES,

TURKEY VULTURES, EAGLES, SEAGULLS and RAVENS.

Where do we HUMANS fit because many of us EAT both PLANT and ANIMALS?

We, along with black bears and red-wing blackbirds are OMNIVORES because we feed on both producers and consumers.

Each step in this series of feeding relationships is known as a TROPHIC LEVEL.

Producers and consumers are linked together in FOOD CHAINS: a SEQUENCE of organisms through which ENERGY IS PASSED.

Here is an example of a food chain in the Lake Winnipeg ecosystem consisting of four TROPHIC LEVELS:

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Energy in Ecosystems (Pg. 22)

Example Food ChainLake Winnipeg Ecosystem

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Trop

hic

Leve

ls

Food Webs

Because animals typically feed on more that one type of organism, food chains become CONNECTED in a COMPLEX relationship known as a FOOD WEB. (A food web is many food chains that are connected together).

Food Webs are MORE REALISTIC than food chains.

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Algae

Larvae

Stickleback

Larger Fish Ex) Northern Pike

The ARROWS show how the sun’s ENERGY FLOWS through an ecosystem from the sun, to producers, to consumers, and to decomposers.

Because plants and animals DIE AT ALL POINTS in food chains, DECOMPOSERS are found at ALL trophic levels in ecosystems.

The diagram below shows the food web of the Lake Winnipeg ecosystem.

Here is another example of a food web.

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Ecological Pyramids

Ecologists use ECOLOGICAL PYRAMIDS to describe the ENERGY FLOW among the TROPHIC LEVELS.

You can visualize the total amount of incoming energy at each level in an ecosystem as a pyramid of energy.

The area at the BOTTOM of the energy pyramid represents the GREATEST amount of energy in an ecosystem.

As the energy passes from producers to consumers, LESS is available in each SUCCESSIVE trophic level.

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Pyramid of Energy

EMBED MSPhotoEd.3

All the energy originates in the sun.

Only 10% of the ENERGY is PASSED ON from one TROPHIC LEVEL to another.

This is because NOT ALL of the ENERGY that an organism takes in is transformed into FOOD. Energy is used by the organism for a variety of life processes such as:

BREATHING TRANSPORTING

MATERIALS

MOVEMENT REPRODUCTION

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Only a PORTION of the ENERGY used goes into building ORGANIC COMPOUNDS that can be EATEN by the next TROPHIC LEVEL.

As a result, only about 10% of the ENERGY taken in at one trophic level is PASSED ON to the next level.

LESS AND LESS energy is available to organisms HIGHER UP the FOOD CHAIN. This explains why there are seldom more than FOUR or FIVE trophic levels in A FOOD CHAIN / WEB.

Pyramid of Biomass

Related to the pyramid of energy is the PYRAMID OF BIOMASS. This pyramid shows the TOTAL AMOUNT of LIVING MATERIAL available at each trophic level.

The area at the BOTTOM of the biomass pyramid corresponds to the PRODUCER level. This represents the GREATEST amount of living material.

You should note that a pyramid of biomass does NOT follow the 10% rule that a pyramid of energy does.

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The PYRAMID OF BIOMASS gives the amount of MASS of LIVING MATERIAL existing ON EACH SQUARE METER of ecosystem.

For example, in an ecosystem it takes a LARGE amount of producers such as plants to support a SMALL number of herbivores such as moose. The number of carnivores such as wolves that can be supported by the moose is even SMALLER yet.

Following Energy Movement in Ecosystems (Pg. 34)

Biogeochemical CyclesS2-1-01 Illustrate and explain how carbon, nitrogen, and oxygen are cycled through an ecosystem.

Let’s take a closer look at the interactions between LIVING THINGS and the PHYSICAL ENVIRONMENT in an ecosystem.

While ENERGY flows in a ONE-WAY direction through and ecosystem, NUTRIENTS are RECYCLED over and over again.

Biogeochemical cycles are the processes by which NUTRIENTS move through ORGANISMS and the ENVIRONMENT.

You may be familiar with the water cycle in which water moves from the Earth’s atmosphere to the surface (PRECIPITATION), and back to the atmosphere again (CONDENSATION). Other important nutrients that are recycled are CARBON, OXYGEN and NITROGEN.

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The Carbon CycleThe process by which carbon moves through an ecosystem is called the carbon cycle.

1. PRODUCERS such as green plants and algae TAKE IN a carbon-containing nutrient known as CARBON DIOXIDE (CO2) from the atmosphere.

2. During PHOTOSYNTHESIS, the energy of the sun is used to CONVERT CARBON DIOXIDE INTO GLUCOSE, a type of organic compound.

3. Plants then change glucose into other types of CARBON COMPOUNDS.

4. When ANIMALS eat plants and algae, the carbon compounds are converted into GLUCOSE.

5. The GLUCOSE is then CONVERTED into CARBON DIOXIDE and energy in a process known as CELLULAR RESPIRATION. The energy is used by organisms for growth, movement, reproduction, excreting wastes, digesting food, and so on.

6. The carbon dioxide is released into the ATMOSPHERE, and the cycle continues.

FOSSIL FUELS are carbon-containing compounds such as petroleum, coal and natural gas that are burned by humans to produce energy. The COMBUSTION of fossil fuels also releases carbon dioxide into to Earth’s atmosphere. The energy is then used to heat our homes and run our automobiles and factories.

Photosynthesis:CO2 + H2O + LIGHT ENERGY C 6H12O6 + O2

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Cellular respiration:O2 + C6H12O6 CO 2 + H2O + ENERGY

Plants (producers) perform PHOTOSYNTHESIS and CELLULAR RESPIRATION.

Animals (consumers) can only perform CELLULAR RESPIRATION.

Carbon gets cycled back and forth between photosynthesis and cellular respiration (carbon gets cycles back and forth between CO2 and C6H12O6.

Oxygen Cycle The oxygen cycle, which moves oxygen through an ecosystem, is closely linked to the carbon cycle.

1. Plants use water during PHOTOSYNTHESIS and release OXYGEN GAS (O2) into the atmosphere.

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2. ORGANISMS then USE the OXYGEN gas during CELLULAR RESPIRATION and release water into the atmosphere.

3. The cycle continues as PLANTS PRODUCE OXYGEN during PHOTOSYNTHESIS, which is then used by organisms in cellular respiration.

Nitrogen Cycle The process by which nitrogen moves through an ecosystem is known as the nitrogen cycle. Nitrogen is an important nutrient found in all living things and is used to build PROTEINS.

While NITROGEN GAS (N2) makes up about 78% of the Earth’s atmosphere, most living things CANNOT use it in this form.

Nitrogen fixation:NITROGEN FIXATION is required to change NITROGEN in the atmosphere into NITRATES and AMMONIA (a form of nitrogen that plants CAN use).

There are 2 methods for nitrogen fixation:1. LIGHTNING – energy from the lightning causes the nitrogen

gas (N2) and oxygen gas (O2) in the atmosphere to react and form NITRATE.

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the nitrate DISSOLVES into the RAIN and falls into the soil

2. CERTAIN BACTERIA – change nitrogen gas into NITRATE and AMMONIA.

The process occurs in BACTERIA that live in the ROOTS of LEGUME plants. o Legumes include CLOVER, ALFALFA, BEANS

and PEAS. The process CAN occur in SOME BACTERIA that

are FREE in the soil also.

ALL PLANTS then CONVERT the NITRATE and AMMONIA produced into a variety of plant proteins.

When ANIMALS eat plants, they CONVERT PLANT PROTEIN into animal protein. For example, when you eat meat or foods containing plant matter (bread, pasta, etc.), your body converts the protein into muscle, hair, fingernails and other animal proteins.

When plants and animals die, DECOMPOSERS break down their remains.

Some BACTERIA and FUNGI cause PROTEINS to decay into NITRATE and AMMONIA, which can then be TAKEN UP AGAIN by plants and used to make proteins.

DenitrificationOther bacteria will convert NITRATE and AMMONIA back into NITROGEN GAS in a process is known as DENITRIFICATION.

This process also occurs when BACTERIA CONVERT ANIMAL WASTE (e.g. sewage), and PLANT WASTE (e.g. dead leaves) into nitrogen gas.

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In all of the examples of the Nitrogen Cycle notice the processes of NITROGEN FIXATION and DENITRIFICATION are required to maintain the cycle.

Nitrogen fixation is needed to change atmospheric nitrogen into a form plants can use.

Denitrification breaks down nitrogen containing compounds and returns the nitrogen to the atmosphere.

Disturbing the CyclesS2-1-02 Discuss factors that may disturb biogeochemical cycles. Include: natural

events, human activities.

The biogeochemical cycles we have studied can be disturbed by many factors, some natural, some caused by human activities:

Disturbing the Carbon Cycle: 1. Natural Events

Examples include: FOREST FIRES

o the COMBUSTION, or burning of plant material such as wood, leaves, or stubble RELEASES LARGE AMOUNTS of CARBON DIOXIDE into the atmosphere

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VOLCANOES o volcanic activity can break down rocks containing

carbon compounds and RELEASE CARBON DIOXIDE into the atmosphere

o the ash generated from a volcano can also BLOCK SUNLIGHT from reaching the Earth’s surface and this may REDUCE the amount PHOTOSYNTHESIS done by plants, which could cause the amount of CARBON DIOXIDE in the atmosphere to INCREASE

2. Human Activities Examples include: DEFORESTATION

o forests are cleared to create more land for farming and to allow towns and cities to grow

o deforestation results in fewer plants REMOVING LESS CARBON DIOXIDE from the atmosphere

BURNING OF FOSSIL FUELS o fossil fuels such as GASOLINE, COAL and

NATURAL GAS that we burn to produce energy also release carbon dioxide into to Earth’s atmosphere (combustion reactions)

Current Issue – The Greenhouse effectThe amount of carbon dioxide in our atmosphere has increased in the past 150 years corresponding to our increased use of fossil fuels for home heating, transportation, and production of goods by industry there is a concern that the increased amount of carbon dioxide in the atmosphere will lead to global warming (THE GREENHOUSE EFFECT)

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Since the population of the earth is now so large, the effects of deforestation, that is removing trees that use carbon dioxide, and the increased amount of combustion for heating homes and industry, human activity now plays a significant role in the Carbon Cycle..

Disturbing the Nitrogen Cycle: Too much nitrogen can be a problem:

1. In the ATMOSPHERE can produce acid rain. 2. In the WATER causes algae blooms3. On LAND leeches into watersheds/gases into

atmosphere.

The disruption of the nitrogen cycle is due mostly to HUMAN ACTIVITIES:

Examples include: Farmers will ADD FERTILIZER to their fields in the late

spring, which contains NITRATE and AMMONIA to improve plant growth.

Nitrate and ammonia are also found in a wide variety of substances including:

O HUMAN SEWAGE O PET AND LIVESTOCK FECES (SOLID WASTE) O LAWN AND GARDEN FERTILIZERS O ERODED SOIL O INDUSTRIAL WASTE O HOUSEHOLD WASTEWATER (DETERGENTS)

Nitrates, Ammonia and Aquatic Ecosystems - Most of the nitrogen (nitrates/ammonia) from the above

sources will eventually end up in an AQUATIC

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ECOSYSTEM. o A recent study concluded that the amount of nitrogen-

containing compounds in Lake Winnipeg increased by 13 % in the last thirty years.

- Excess NITRATES and AMMONIA results in frequent ALGAL BLOOMS and EXCESSIVE WEED BEDS along the shoreline.

- Algal blooms:o Can produce dangerous TOXINS, which can harm

FISH, WILDLIFE, and HUMANS. Can cause skin irritation, nausea, diarrhea, etc.

o Affects drinking water quality (taste, smell)o Chokes out aquatic plants by preventing sunlight from

reaching them.

Eventually the algal blooms “CRASH” and the algae begin to die. The DECOMPOSING WEEDS and ALGAE deplete OXYGEN from the water.

Many fish will die due to a LACK OF OXYGEN.

Farm Runoff The AGRICULTURAL INDUSTRY is another source of NITRATE and AMMONIA entering Manitoba’s LAKES and RIVERS.

1. LIVESTOCK OPERATIONS o produce large quantities of ANIMAL FECES.o The disposal of this MANURE is monitored/controlled

so that large amounts of manure are not washed into lakes and rivers during SNOWMELT, or heavy RAINSTORMS.

2. FERTILIZERS

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o Soil may erode and fertilizers may WASH OFF farmland during the spring SNOWMELT, or in heavy RAINSTORMS.

o The ammonia and nitrates can also SEEP into the GROUND and enter the GROUND WATER.

The ingestion of nitrates can cause anemia, a blood disorder, in children.

Human Sewage and Wastewater - In larger communities, SEWAGE (human liquid and solid

waste) and WASTEWATER (dirty water from sinks and showers) is collected and sent to a water treatment plant.

- When the water is mostly cleaned of the waste, the water is RETURNED to a LAKE or RIVER.

- In rural communities, homes are connected to individual SEPTIC FIELDS where wastes are broken down by bacteria. The clean water then drains into the ground.

- Occasionally problems with septic fields and treatment plants occur, releasing wastewater and sewage into the ground/lake/river.

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Bioaccumulation

S2-1-03 Describe bioaccumulation and explain its potential impact on consumers. Examples: bioaccumulations of DDT, lead, dioxins, PCBs, mercury...

In an ecosystem undisturbed by man, organisms are born, live, reproduce and die. Materials needed for life are CYCLED through the ecosystem.

When humans appear in an ecosystem, CHEMICALS produced by human activity in HOUSEHOLDS and INDUSTRIES are released into the environment. Humans even spread chemicals deliberately to kill certain organisms that they call pests.

These POISONS were NOT part of the ecosystem initially. There may be no way for the ecosystem to RID ITSELF of the poisons.

If there is NO CYCLE to do this, what happens to the poisons and how is the ecosystem affected by them?

Biodegradable and Non-biodegradable Substances

Recall that:DECOMPOSERS break down substances into the BASIC NUTRIENTS from which they were made.

Biodegradable Substances- Substances that are BROKEN DOWN NATURALLY in the

environment.- Examples of BIODEGRADABLE substances include:

SEWAGE FOOD SCRAPS

DEAD ORGANISMS

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Non-Biodegradable Substances- substances that are broken down very SLOWLY or NOT

BROKEN DOWN AT ALL by natural processes. - Once these pollutants enter an ecosystem, they will remain

there FOREVER. - Examples of NON-BIODEGRADABLE substances include:

DDT (a pesticide) MERCURY GLASS

certain types of PLASTICS

A POLLUTANT becomes a TOXIN when it adversely affects living organisms. Examples of toxins include DDT and MERCURY.

What happens when non-biodegradable substances enter ecosystems?

- When producers like PLANTS and ALGAE take in WATER for PHOTOSYNTHESIS, they can also ABSORB small AMOUNTS of non-biodegradable substances.

- Because these substances CANNOT be USED nor BROKEN DOWN, they are STORED in the plant.

- The toxins begin to ACCUMULATE inside the PRODUCERS and become part of the FOOD CHAIN.

- When HERBIVORES eat the plants containing the non-biodegradable substances, they too begin to STORE the TOXINS in their FAT.

- Because MANY PRODUCERS must be EATEN to keep one herbivore alive, the AMOUNT of TOXIN inside one HERBIVORE is much HIGHER than that of the INDIVIDUAL PRODUCERS it CONSUMED.

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- The STORED TOXINS continue to be PASSED UP the food chain, moving from primary to secondary to tertiary consumer.

- At each TROPHIC LEVEL the amount of TOXIN inside the organisms INCREASES, because each PREDATOR must eat MANY PREY.

This process is known as BIOACCUMULATION or BIOAMPLIFICATION.

Eventually the LEVELS of the TOXIN become HIGH ENOUGH inside the SECONDARY or TERTIARY CONSUMERS that their HEALTH is AFFECTED. They may be POISONED and DIE, or WEAKENED and more susceptible to DISEASE or PREDATORS.

Example:Bioaccumulation of DDT

Starting in the 1940’s this chemical was sprayed on crops to control insects. In the 1950’s and 1960’s the number of BIRDS OF PREY such as peregrine FALCON, HAWKS and EAGLES began to decline rapidly.

Examine the food chain in the diagram below.

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- WHEAT was sprayed with DDT to kill insects that fed on it.- When GRASSHOPPERS ate the wheat many died, but

some survived. o The DDT was passed from the PRODUCER trophic

level (wheat) to the PRIMARY CONSUMER trophic level (grasshopper).

- The DDT continued to move up the food chain and its concentration INCREASED in the tissues of the SECONDARY CONSUMERS (red-wing blackbirds) and TERTIARY CONSUMERS (peregrine falcons).

By the 1970’s the peregrine FALCON population in North America was almost WIPED out. The high concentrations of DDT in the birds had caused their EGGSHELLS to become THIN and BREAK, reducing the numbers of chicks that hatched. The DDT also AFFECTED the bird’s BEHAVIOUR causing them to abandon their nests and chicks.

The use of DDT has been restricted in Canada since 1969. Unfortunately, DDT is non-biodegradable, and has continued to persist in the environment. It is STILL FOUND in the TISSUES of higher-level consumers to this day, but the amounts are declining. As a result, the peregrine falcons are making slow recovery in Canada.

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Population DynamicsS2-1-04 Discuss the carrying capacity of an ecosystem.S2-1-06 Construct and interperet graphs of population dynamics.

A POPULATION is a group of organisms that belong to the SAME SPECIES that live in a CERTAIN AREA.

For example, all the flies that live in your house are a population, just like all the people that live in Winnipeg.

Exponential Population Growth

When conditions are IDEAL for GROWTH and REPRODUCTION, a population will experience a RAPID INCREASE in size.

Initially the population grows SLOWLY, but the LARGER the population gets, the FASTER it GROWS.

As more offspring survive and reproduce, even MORE offspring are born.

The graph below illustrates a population growth curve of this nature. This type of population growth curve is called and EXPONENTIAL growth curve and is shaped like the letter “J”.

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This population is growing under IDEAL CONDITIONS. This curve has the shape of a “J”

Can a population continue to grow at this rate forever? The answer of course, is NO.

Logistic Growth Curve

The ENVIRONMENT begins to LIMIT population GROWTH. Resources such as FOOD, WATER, and SPACE become SCARCER and the rate of population INCREASE begins to SLOW.

The graph below illustrates a curve of this nature called a LOGISTIC population growth curve. This curve has the shape of the letter “S”.

In REAL LIFE or RESTRICTED situation, a population CANNOT grow indefinitely. Eventually, as food and space run out, the rate of population growth slows and the population becomes CONSTANT. This forms a curve with the shape of an “S”.

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Closed Populations

A CLOSED population occurs when NEW INDIVIDUALS cannot enter (IMMIGRATE) an existing population, and EXISTING INDIVIDUALS cannot leave (EMIGRATE).

In a closed population only BIRTHS or NATALITY INCREASE the population and only DEATHS or MORTALITY DECREASE the population of a certain organism in an ecosystem.

Example: a deer population living on an isolated island. No deer can enter or leave the island.

Therefore the population of the deer will increase only if deer are born and decrease only if deer die.

If 45 deer now live on the island and 25 deer are born and 20 deer die during the next year, then, the population growth for the year will be found as follows:

Population growth = births – deaths = 25 - 20 = 5

The population grows by 5 from 45 to 50 deer.

Open Populations

Deer found in the forests of Manitoba are considered to be part of OPEN POPULATIONS. In this kind of population, besides being born or dying, deer can LEAVE the population and move to another area or EMIGRATE. Deer from other areas can travel INTO the ecosystem or IMMIGRATE.

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IMMIGRATION and BIRTHS INCREASE the population. EMIGRATION and DEATHS DECREASE the population.

The formula for determining population growth in an open system is as follows:

POPULATION GROWTH = (BIRTHS + IMMIGRANTS) – (DEATHS + EMIGRANTS)

If population growth is LESS THAN ZERO, there are MORE DEATHS and EMIGRANTS in the population THAN there are BIRTHS and IMMIGRANTS. The size of the population begins to decline.

Carrying Capacity

The LARGEST population of a species that a PARTICULAR ENVIRONMENT can SUPPORT is known as the CARRYING CAPACITY.

The CARRYING CAPACITY of the environment is different at DIFFERENT TIMES.

The carrying capacity is AFFECTED by many FACTORS. At some times when RESOURCES such as FOOD and WATER are more ABUNDANT, a population can INCREASE in size. At other times RESOURCES may be SCARCER, causing the population to DECLINE.

These population FLUCTUATIONS occur OVER TIME, but the CARRYING CAPACITY represents an AVERAGE of a series of UPS and DOWNS.

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If you DRAW A LINE through the MIDDLE of the population FLUCTUATIONS, that line represents the CARRYING CAPACITY of that environment for that species.

POPULATION GROWTH CURVE: CARRYING CAPACITY

The population of a species in an ecosystem will grow RAPIDLY AT FIRST. Once the population has reached the level that the ecosystem can support, the population varies UP and DOWN around the CARRYING CAPACITY.

Population Distributions According to Age

As well as showing how POPULATION CHANGES WITH TIME, which is the purpose of a GROWTH CURVE, it is also useful to consider HOW MANY organisms there are of a CERTAIN AGE within a population. This information can also indicate whether the population will remain STEADY, or INCREASE as time goes on, or DECREASE with time.

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Population-age distributions are drawn as HISTOGRAMS with POPULATION along the HORIZONTAL axis and AGE along the VERTICAL axis. The graph is drawn with horizontal bars. Each bar represents the number of organisms of a certain AGE GROUP. There are as many bars as age groups. There is ONE bar for MALES and one bar for FEMALES.

An age-population histogram shows a SNAPSHOT of the organisms, both male and female, that fall into categories of age. While the data represented is for only a particular INSTANT in TIME, the SHAPE of the DISTRIBUTION allows us to PREDICT if the population is increasing, decreasing or steady.

Increasing Population Histograms

The shape of the histogram will tell you whether the population is steady, increasing or decreasing.

INCREASING POPULATIONS

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In this population distribution MANY OFFSPRING are being produced by the organisms of REPRODUCTIVE AGE. Therefore, as the population ages, there will be MANY YOUNG ORGANISMS to REPLACE the CURRENT PARENTS and have offspring of their own.

This age-population histogram has the shape of a PYRAMID with a wide base. The wide base means there are LOTS OF YOUNG ORGANISMS to REPLACE the OLDER ONES WHO DIE OFF. The population INCREASES since there are FEWER older organisms dying and many MORE organisms being born.

Decreasing Population Histogram

DECREASING POPULATIONS

In this population distribution there are MANY organisms of REPRODUCTIVE AGE but they are having FEW OFFSPRING. Therefore, as the population ages, there will be FEWER young organisms to REPLACE the CURRENT PARENTS and have offspring of their own.

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This histogram has the WIDEST part in the MIDDLE section. In this age-population distribution, there are FEW YOUNG ORGANISMS to REPLACE the OLDER ORGANISMS as they die off. Also, in LATER YEARS, there will be FEWER organisms to REPRODUCE and supply the OFFSPRING needed to replace those which are now the young. The population DECREASES.

Steady Population Histogram

STEADY POPULATIONS

In this population distribution organisms of REPRODUCTIVE AGE are having JUST ENOUGH offspring to REPLACE THEMSELVES. Therefore, as the population ages, there will be ENOUGH YOUNG ORGANISMS to REPLACE the CURRENT PARENTS and have offspring of their own.

In this age-population distribution the REPRODUCING ORGANISMS are simply REPLACING THEMSELVES. Since there are as many organisms being BORN as are DYING, the population remains STEADY.

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Factors Limiting Population GrowthS2-1-05 Investigate and discuss various limiting factors that influence population dynamics. Include: density dependant and density independent factors.

As was discussed during the carrying capacity section, the size of a population CANNOT continue to increase indefinitely.

Many ENVIRONMENTAL factors LIMIT the growth of a population. For example, RESOURCES such as FOOD and WATER will affect the size of a population.

What are the factors that influence the size of a population?

Density-dependent Limiting Factors

DENSITY-DEPENDENT FACTORS tend to operate when a POPULATION is LARGE and CROWDED.

If the population DENSITY, the NUMBER of organisms PER SQUARE KILOMETRE (or per cubic meter) becomes TOO HIGH, density dependent factors begin to act to LIMIT the population of that species. These density-dependent factors become important ONLY when the population DENSITY is TOO LARGE.

These limiting factors include: COMPETITION PREDATION DISEASE STRESS

Density-dependent factors act to DECREASE the SIZE of a population by INCREASING the DEATH RATE and DECREASING the BIRTH RATE.

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A. Competition All living things require certain RESOURCES for SURVIVAL.

Animals require FOOD, WATER, SHELTER and LIVING SPACE.

Plants require WATER, SUNLIGHT and LIVING SPACE.

As the size of a population INCREASES, the organisms in the population are forced to COMPETE to obtain ENOUGH resources to SURVIVE.

Example: Herd of cattle As the number of cows in a pasture INCREASES, there

may no longer be enough GRASS to support all the cattle. They will begin to struggle to find enough grass to eat. They may begin to lose weight, and some may die of

STARVATION.

B. Predation

PREDATION occurs when one organism (the PREY) serves as food for another (the PREDATOR). One PREDATOR-PREY relationship in Manitoba is polar bears feeding on seals: If a group of seals in an area has had plenty of food, the SEAL POPULATION will begin to INCREASE.

Because polar bears prey on seals, the number of POLAR BEARS in the area will also INCREASE because there is lots of food.

More polar bears (predators) will eat more seals (prey). So the number of SEALS will DECLINE.

With fewer seals to eat the POLAR BEARS will begin to starve, and their numbers will begin to DECLINE.

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When only a FEW polar BEARS are left, the SEALS have a greater chance of SURVIVING, and once again their numbers will begin to RISE.

C. Disease

When the population is large and crowded, there is LESS SPACE between SPECIES causing DISEASES to be transmitted FASTER and more EASILY.

Example: Dutch elm disease If an elm tree gets infected with the fungus that causes

Dutch elm disease, it will eventually die. If there are LOTS of other elms NEARBY, the fungus can

easily SPREAD and kill more elms. If the trees are more widely SEPARATED, the disease

CANNOT spread as easily and as fast.

D. Stress

All organisms require a certain amount of LIVING SPACE.

In some animals, OVERCROWDING can lead to INCREASED AGGRESSION and FIGHTS over territory, resulting in INJURIES and STRESS. Adults may be WOUNDED, and their offspring may be NEGLECTED or ORPHANED.

In other animals, stress can cause PREGNANT females to MISCARRY, or STOP producing eggs. In any case, more animals in the populations will die, and their numbers will decrease.

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Density-independent factors

Density-independent factors affect a population REGARDLESS its size. These limiting factors include:

NATURAL occurrences HUMAN activity.

Density-dependent factors also act to DECREASE the size of a population by INCREASING the DEATH RATE and DECREASING the BIRTH RATE.

A. Natural Occurrences

These are events that occur WITHOUT HUMAN intervention. For example:

a LIGHTNING STRIKE in a forest can cause a fire that kills most of the plants and animals in an area

a FROST will wipe out many insects and annual plants a winter with HEAVY SNOWFALL may make it difficult for

deer to obtain enough grass to survive (conversely, a warm winter with little snowfall may cause deer populations to increase)

B. Human Activity

Humans can have a significant impact on the populations of other organisms.

For example: a forest may be CLEAR-CUT, reducing the number of trees

in an area marshes may be DRAINED, resulting in the loss of habitat

for plant, small mammals and birds.

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Areas that were home to a variety of plants and animals may become housing DEVELOPMENTS and SHOPPING MALLS

On the other hand, human interventions such as STOCKING deer and bird FEEDERS, and CONSTRUCTING nesting boxes may result in higher survival rates.

Population Dynamics – Predator-Prey RelationshipsSee Lynx-Hare ExerciseSee Wolf-Deer Population

In a nutshell: the prey population INCREASES, when the population of the

predator is LOW and FOOD is plentiful this increases the availability of food for the PREDATOR this then results in an INCREASE in the predator population,

but LAGGING behind the prey population increase in TIME.

A large PREY population results in COMPETITION for food, STARVATION and a LOWER birth rate

as the predator population INCREASES, there is more PREDATION and the prey population DECREASES

now the predator have LESS food and their population also DECREASES due to STARVATION and a LOWER birth rate, but, again this decrease is LAGGING behind the decrease in PREY population

The CYCLE begins to REPEAT itself as the prey population now begins to increase with fewer predators to eat them and more food available to the hares.

The TWO population curves FOLLOW the same SHAPE.

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The peaks and valleys of the predator curve trail the peaks and valleys of the prey curve.

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BiodiversityS2 1-08 Observe and document a range of organisms that illustrate the biodiversity

Look outside. What different types of plants and animals do you see? Do you recognize any birds or mammals? What about trees and shrubs? How many different species can you see?

The VARIETY of ORGANISMS found within an ECOSYSTEM is known as its BIODIVERSITY.

The BIODIVERSITY of an ecosystem is an INDICATOR of its STABILITY and HEALTH.

STABLE and HEALTHY ecosystems will have a LARGE NUMBER and VARIETY of SPECIES present.

Different types of ECOSYSTEMS have differing numbers ORGANISMS present.

The producers, consumers and decomposers in a Brazil’s TROPICAL RAINFOREST are quite different from those in Canada’s TUNDRA. A rainforest has a LARGE number of species at each trophic level. There are many different FOOD CHAINS and the resulting food WEB is very COMPLEX.

In Canada’s tundra there are FEW species. The food chains are SMALL in number and the food web is relatively SIMPLE. DIFFERENT types of ecosystems contain DIFFERENT organisms. You don’t see many polar bears in Brazil, and you don’t see many parrots in the Arctic!

The ORGANISMS living in the ecosystem have ADAPTED to that ENVIRONMENT. Each organism has an ECOLOGICAL NICHE.

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This refers to the ROLE the organism plays in the ecosystem, that is, everything an organism does to SURVIVE and REPRODUCE.

The BIODIVERSITY of an ecosystem may also appear to CHANGE through the YEAR. You certainly do not see many mosquitoes or robins here in the winter!

BIODIVERSITY is greatly AFFECTED by HUMAN ACTIVITY.

Example: Winnipeg Area The area around Winnipeg was once covered with a

FOREST of trees. As the area was SETTLED by farmers, the forests were

CLEARED and the wetlands were DRAINED to provide land for AGRICULTURE.

The destruction of the HABITAT of the species that lived there REDUCED their POPULATIONS or forced the species to MOVE to different areas.

HUNTING also reduced the population of predators like wolves, bears and coyotes that preyed on livestock.

This kind of activity is still occurring in various parts of the world such as the RAIN FORESTS of South and Central America.

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Sustainability

S2-1-09 Explain how the biodiversity of an ecosystem contributes to its sustainability.

STABLE and HEALTHY ecosystems are SUSTAINABLE they are RENEWABLE and can CONTINUE without the

addition of NEW MATERIALS.

They RELY on:the UNDISTURBED CYCLING OF NUTRIENTS, and the natural BIODIVERSITY of the area to maintain PREDATOR-PREY relationships.

Compare the SUSTAINABILITY of a natural PRAIRIE GRASSLAND to that of a HOMEOWNER’S LAWN. The BIODIVERSITY of the grassland is much GREATER than that of the lawn.

Prairie Grassland:Different plants, including those that can “FIX” nitrogen are present. A VARIETY animals and insects also live in the grasslands. There are HERBIVORES such as mice, gophers, and deer. There are CARNIVORES such as coyotes and hawks. Insects such as bees pollinate flowers. Other insects feed on the plants and help to RECYCLE dead plant and animal material. ENERGY and MATERIALS flow through the ecosystem.

The BIODIVERSITY of a natural prairie grassland helps PROTECT it from PREDATORS. While grasshoppers consume grasses, their population is kept in check by predators such as red-wing blackbirds. Other plant species may not be harmed by grasshoppers, and will continue to grow.

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Lawn:In contrast, a lawn is a MONOCULTURE. Only ONE type of plant (grass) is present. As grasses CANNOT “fix” nitrogen, the lawn ecosystem can ONLY be SUSTAINED with the addition of FERTILIZER on a regular basis.

Monocultures are more susceptible to PESTS. Their large CONCENTRATION of a small number of SPECIES makes them more vulnerable to attack. A lawn requires the addition of herbicides to keep it weed-free, and the addition of insecticides to reduce the damage caused by insects.

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Declining PopulationsS2-1-07 Describe potential consequences of introducing new species and species extinction on an ecosystem.

Previously, it was observed that the population of a given species tends to FLUCTUATE NATURALLY but remain at a fairly CONSTANT value determined by the CARRYING CAPACITY of the ecosystem.

If the ecosystem changes, for example, by having favorable weather for an extended period of time, the carrying capacity will increase and the population of a given species will increase.

However, if the CARRYING CAPACITY of the ecosystem DECREASES, then the POPULATION of a given species will DECREASE as well. The decline in population can lead to that species DISAPPEARING ENTIRELY. The species are classified as AT-RISK SPECIES.

As the POPULATION of a SPECIES DECLINES it goes through STAGES depending on the SIZE of the population decrease.

Stage 1: VULNERABLE this is any species that is at risk because of LOW or

DECLINING numbers at the FRINGE of its range or in some RESTRICTED AREA

an example is the grey fox in Southern Ontario.

Stage 2: THREATENED this is any species that is LIKELY to become

ENDANGERED if factors that make it vulnerable are NOT REVERSED

there are very few wood bison because the forests have been cut down.

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Stage 3: EXTIRPATED. this refers to a species that NO LONGER EXISTS in ONE

PART of Canada BUT EXISTS in OTHER PARTS of Canada.

Stage 4: ENDANGERED. this refers to a species that is CLOSE to EXTINCTION in

ALL PARTS of CANADA or in a significantly LARGE REGION

the eastern cougar is sighted very rarely.

Stage 5: EXTINCT. this is a species that is NO LONGER FOUND anywhere on

EARTH the blue walleye, a Great Lakes fish, no longer exists

anywhere.

POPULATION GROWTH CURVELEADING TO EXTINCTION

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Example: Polar Bears near Churchill Manitoba

- There is a large concentration of polar bears in northern Manitoba

- They live on the ice in Hudson’s Bay from mid November to Late July, filling up on fish and SEALS.

- When the ice melts they move to the land and survive on stored FAT.

- Our CHANGING CLIMATE has caused the ice to melt much sooner, resulting in a SHORTER hunting season.

- This has lead to polar bears becoming a THREATENED species.

Introduction of New SpeciesThe introduction of new species can also cause changes in ecosystems and the populations of species:

- The SUSTAINABILITY of the ecosystem can be INCREASED or DECREASED,

- FOOD CHAINS can become ENHANCED or DISRUPTED - RESOURCES can be INCREASED or DEPLETED.

Sometimes new species are introduced to IMPROVE BIODIVERSITY, or to help CONTROL populations.

Other times, new species are introduced by ACCIDENT, and they INVADE the ecosystem INVASIVE SPECIES

Examples include: ZEBRA MUSSELS, RUSTY CRAYFISH, PURPLE LOOSTRIFE, etc.

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Effects of Extinction

Recall that organisms are linked together in COMPLEX FOOD WEBS. Should one species in an ecosystem go EXTINCT, the entire food web may be JEOPARDIZED. Extinction DISTURBS PREDATOR-PREY relationships.

How would the removal of algae affect the Lake Winnipeg ecosystem?

- It is an important food source for PRIMARY CONSUMERS such as INSECTS.

- A lack of algae could result in a shortage of food for these PRIMARY CONSUMERS.

- The INSECT populations will begin to DECLINE. - Thus populations of SECONDARY CONSUMERS that

PREY also decline. - The number of minnows and catfish would be REDUCED. - The number of TERTIARY CONSUMER populations, the

whitefish and northern pike, would begin to FALL as well. - Finally, the TOP CONSUMERS, the eagles would dwindle in

number.

You can see how the removal of one species can have a large impact on an ecosystem. It can lead to a DOMINO EFFECT – one event can cause a large CHAIN REACTION.

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PollutionS2-1-10 Investigate how human activities affect an ecosystem.

For many years you have heard of pollution. In biology, pollution is defined as:

1. The CHANGING of a natural environment, either by NATURAL or ARTIFICIAL means, so that the environment becomes HARMFUL to the living things NORMALLY found in it. Most often this refers to the INPUT of TOXIC CHEMICALS into the environment.

2. The CONTAMINATION of WATER (such as from raw sewage, industrial waste), making it unfit to support many forms of life.

In MANY instances, pollution is the result of HUMAN ACTIVITY.

Various human activities release harmful chemicals into the AIR, the GROUND or the WATER. The environment then becomes harmful to the organisms that are naturally found there.

Pollution of the Air

Air Pollution is mostly caused by two human activities: - BURNING FOSSIL FUELS, - RELEASE of CHEMICALS by INDUSTRY.

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A. Greenhouse Effect

Much of our energy is created through the combustion of fossil fuels:

Hydrocarbon + O2 CO2 + H2O + Energy

By burning fossil fuels in the engines of CARS, POWER PLANTS, FURNACES etc. we upset the carbon cycle.

More carbon is entering the atmosphere as CARBON DIOXIDE than is removed by PHOTOSYNTHESIS.

The result is the build up of CARBON DIOXIDE in the air which contributes to the GREENHOUSE EFFECT.

ENERGY from the sun enters travels to the earth but is TRAPPED (not reflected) back out.

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As a result, average global temperatures begin to rise, causing changes in CLIMATES all around the world.

The changing climate impacts ECOSYSTEMS by making it UNSUITABLE for the organisms in to live in them (ex. POLAR BEARS, migrating BIRDS, PENGUINS, etc.)

Carbon dioxide is not the only Greenhouse gas the human activity is causing to accumulate in the atmosphere:

1. METHANE (CH4)- released by RICE cultivation, ANIMALS being raised for food, BIOMASS burning, and DECOMPOSING materials in LANDFILLS.

2. DINITROGEN MONOXIDE (N2O)- released by the use of FERTILIZERS in agriculture, the production of NITRIC ACID in industry, and AUTOMOBILE exhaust.

B. Depletion of the Ozone Layer

The earth has a THIN PROTECTIVE LAYER high up in the atmosphere that shields us from harmful UV (ultraviolet) radiation.

That thin protective layer is the OZONE LAYER.

CHLOROFLUOROCARBONS (CFC’s) - Manmade compounds that were used as REFRIGERANTS

in air conditioners/refrigerators and in AEROSOL spray cans. (ex. FREON)

- CFC’s travel high in the atmosphere, and cause OZONE (O3) to be BROKEN DOWN into oxygen (O2)

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- More UV radiation reaches the earth, affecting human health (CANCERS) and some CROPS.

- CFC’s were BANNED in an international treaty called the MONTREAL PROTOCOL in the early 1990’S by almost all countries (some small poorer nations did not sign the treaty).

Recently, some scientists have reported that it appears the ozone layer is starting to repair itself and could be fully repaired in about 50 years.

C. Acid Rain

In addition to the greenhouse effect, the burning of fossil fuels like COAL, GASOLINE, DIESEL, also contributes to ACID RAIN.

- When coal containing sulphur is burned, it can produce SULPHUR DIOXIDE and SULPHUR TRIOXIDE.

- The sulphur oxides DISSOLVE into the WATER in the ATMOSPHERE.

- When the water falls as rain, it has an ACIDIC nature, a LOW p H .

- Since many organisms live in water that is NEUTRAL the acid rain is HARMFUL to them.

- FISH STOCKS are destroyed in lakes and FORESTS are killed by the high acid content of the rain.

Car engines can also produce NITROGEN OXIDES that can also too dissolve in water in the atmosphere and fall as acid rain.

Since the automobile and industry are concentrated in CITIES, the problems of air pollution can be more SEVERE in cities. Cities like Toronto and Los Angeles experience photochemical smog that makes it difficult to breathe for people with respiratory problems like asthma.

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D. Noise Pollution

In cities, the large number of people, the traffic, airplanes, and industry also produce NOISE. High levels of noise can be harmful to the EARS and also cause ORGANISMS to be STRESSED. For example, loud noises may prevent organisms from resting properly.

Pollution of the Land

The land is polluted by human activity such as discarding WASTE, GARBAGE or items that one no longer has use for.

Most land pollution comes from objects or chemicals that are NONBIODEGRADEABLE

They DO NOT BREAK DOWN in the environment and accumulate there.

Common examples of NONBIODEGRADEABLE materials are STYROFOAMS and PLASTICS used in most PACKAGING materials.

Last for HUNDREDS of years in the landfill Think about all the PLASTIC BOTTLES we use!

A relatively new type of problematic waste is E-WASTE old COMPUTERS/ELECTRONICS that are thrown out.

Think about all of the things we throw out on a daily basis. It all ends up in the landfill!

The contents of a LANDFILL can SEEP into the SOIL and carry toxic chemicals into the GROUNDWATER that people drink.

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BIODEGRADABLE substances can also pollute the land if TOO MUCH is applied to the land for RECYCLING to occur. Examples include:

- Waste from AGRICULTURAL LIVESTOCK - HERBICIDES and INSECTICIDES used on crops to kill plant

and insect pests. - HOMEOWNERS spraying their lawns (actually apply more

fertilizers/pesticides per square meter than farmers)

Pesticides are NOT SELECTIVE and kill many other PLANTS and INSECTS. They DECREASE BIODIVERSITY and make it difficult for the ecosystem to SUSTAIN itself.

Pollution of the Water

Pollution of the water usually occurs by the DUMPING or LEECHING of contaminants into bodies of water.

- INDUSTRIES may dump CONTAMINANTS into the SEWER.

- SEWAGE from cities Some cities do NOT process the sewage but RELEASE the raw sewage into a nearby river (ex. Winnipeg in a heavy rainstorm)

- PESTICIDES /FERTILIZERS can be carried by SPRING RUNOFF or by water from HEAVY RAINS

- The NITRATES from FERTILIZERS and MANURE can be carried into nearby water bodies.

- Harmful BACTERIA such as E. COLI from livestock waste, can pollute DRINKING WATER leading to the deaths of humans (e.g. WALKERTON, ON in 2000).

The pollutants make their way into the RIVERS and LAKES affecting water QUALITY, as well as causing ALGAL BLOOMS.

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Reducing Pollution

In order to REDUCE the amount of pollution, we must CHANGE our HABITS to make our ACTIVITIES SUSTAINABLE.

As you probably know, we all need to start on a personal level. There are many things we can do:

- REDUCE , REUSE and RECYCLE. - buy things with LESS PACKAGING . - Use less PLASTIC and other non biodegradable materials- Rely LESS on using METALS. - Rely LESS on FOSSIL FUELS and MORE on

RENEWABLE energy sources such as WIND, SOLAR and HYDROELECTRICITY.

- Use ENGINES that burn ALTERNATE fuels instead of fossil fuels.

Sustainability

We must create a society that values the SUSTAINABILITY of our RESOURCES and ENVIRONMENT.

Sustainability is the ability to maintain a certain PROCESS or STATE INDEFINITELY.

In order to make decisions about sustainability, we require knowledge of SOCIAL, ECONOMIC, and ENVIRONMENTAL issues and the RELATIONSHIPS among them.

An important part of sustainability is the idea that our DECISIONS TODAY affect our FUTURE HEALTH and WELL-BEING, the ECONOMY and the ENVIRONMENT. We are here on earth now, BORROWING it from our GRANDCHILDREN. We must ensure that we leave the earth UNSPOILED, fully able to support our grandchildren in the manner it presently supports us.

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Sustainable Development Model

SUSTAINABLE DEVELOPMENT is a way of using resources that aims to meet HUMAN needs while preserving the ENVIRONMENT so that these needs can be met not only in the PRESENT, but in the INDEFINITE FUTURE

This model requires us to CHANGE our WAY of LIFE in order to balance the needs of PEOPLE, the ENVIRONMENT and the ECONOMY.

This will allow us to MAINTAIN our QUALITY of LIFE for a long, long time.

Sustainable Development Model

Big decisions made by politicians on our behalf and decisions made by individual citizens like you must keep sustainable development at the forefront of the decision making process.

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