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Science 1206
Unit 1: Sustainability of Ecosystems
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Introduction to Sustainability
TEXT: - p. 86-87
Sustainable system
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A system that can be maintained over time.
A system that meets the needs of both the present and future generations.
In order to be maintained, the system must not sacrifice long term benefits for short
term gains.
To develop a successful sustainable system, society must have a clear idea of the
value of ecosystems.
Resulting decisions must take into account socioeconomic factors and ecological
factors.
o Ex: Clear cutting in South America for farming
o Ex: Dumping mine tailings into ponds
Paradigm
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A view that is widely held by society with respect to a certain concept or belief.
Ex: The Earth is round
Paradigm Shift
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A significant shift in the way humans view a particular concept or idea.
Generally paradigms shifts are rare
We discussed the fishery and how we over exploited the resource.
Ecosystems and Ecology
Ecology
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The study of living organisms and the interactions that exist between them and their
environment.
Ecosystems
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A community of living organisms together with their physical environment.
Composed of 2 types of factors:
1. Abiotic factors –non-living factors including light, temperature, wind,
space, oxygen, water and soil nutrients that influence the ecosystem.
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Unit 1: Sustainability of Ecosystems
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2. Biotic factors – the presence and roles of living things that influence the
ecosystem including plants and animals, bacteria, disease, predation, prey,
competition and symbiosis (mutualism, commensalism, parasitism).
Ecotones
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The transition areas between two bordering ecosystems that contain species from
both bordering systems so they often contain a greater biodiversity than either
ecosystem.
Illustrate how abiotic factors influence the distribution of organisms.
Lab: A Natural Ecosystem – we studied the pond and the river (abiotic and biotic
factors)
The Flow of Energy in Ecosystems
TEXT: - p. 32-33 (energy in ecosystems)
- p. 34-39 (energy movement and pyramid graphs)
Energy in Ecosystems
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The source of all energy in ecosystems is the SUN!
This energy is used by green plants to make sugar (photosynthesis) which serves as
food for all other organisms.
This energy is transferred through ecosystems
Trophic level – how an organism gains its energy
Consider autotrophs vs. heterotrophs:
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Autotrophs
o make their own food from nutrients, sunlight or other non-living resources.
o They are producers.
o Ex: plants, algae, some bacteria
Heterotrophs
o cannot make their own food and must obtain energy from autotrophs or
other heterotrophs.
o They are consumers at ANY trophic level.
Consumers can be:
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Unit 1: Sustainability of Ecosystems
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Herbivores (plant eaters)
Carnivores (meat eaters)
Omnivores (plant and meat eaters)
Saprobes (decomposers) – organisms that break down
detritus (waste from plants and animals including dead
remains). Critical for the recycling of matter in ecosystems by
releasing nutrients into the soil and water which plants and
algae use to grow.
Producers
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autotrophs that make sugar from sunlight and carbon dioxide through
photosynthesis.
1st Trophic Level
Ex: spruce bud
Primary (1) Consumers
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Feed directly on producers.
2nd Trophic Level.
Ex: deer
Secondary (2) Consumers
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rely directly on 1 consumers, indirectly on producers.
3rd Trophic Level.
Ex: wolf
Tertiary (3) Consumers
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4th Trophic Level
Top Carnivore
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5th Trophic Level
Not all the energy from the producer is actually passed on to the 1 consumer. Some is
used for growth and maintenance by the producer. Likewise, not all the energy of the 1 
consumer is available to the 2 consumer. This pattern continues throughout the trophic levels
such that the amount of energy available in each level of a chain of transformations is ALWAYS
less than the amount of energy available at the previous level
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Unit 1: Sustainability of Ecosystems
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Example:
The deer eats only the buds and not the whole tree. The deer uses some of the energy
for growth, maintenance, heat. In addition the deer cannot digest the whole bud and passes
unusable material through the digestive system. The wolf does not eat the whole deer, perhaps
leaving the bones, hooves and fur.
Result: Only about 10% of the energy is available to the next trophic level.
Pyramid Graphs
Activity 1.3: Constructing a Pyramid of Energy
These energy relationships can be expressed using a pyramid of energy where the energy at
each trophic level is measured in kilojoules (kJ) (or in this case kilocalories).
Pyramid of Energy
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Because of the overall loss of energy at each level, the number of trophic levels is limited to
about 5!
WHY? The larger mass of 3 consumers and the large amount of energy expended while
hunting limits the number of individuals that can be supported at the top of the pyramid!
Pyramid of Biomass
Consequently the dry biomass also decreases as the trophic level increases.
Niche and Habitat
TEXT: - p. 40-41 (ecological niche)
How do all these organisms in an ecosystem coexist with each other?
Ecological Niche
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This is an organism’s place in the food web, its habitat, breeding area, and activity.
In other words: the niche an organism fills includes everything it does to survive and
reproduce!
But what exactly is habitat?
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Quite simply – it is the place where a species can live!
Generally: In any ecosystem each species has a different niche. This helps to reduce
competition between species for the same resources and territory.
However: Some niches will overlap but not completely.
Examples: starling vs. robin
What happens when the niches overlap?  Competition!
Competition
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The interaction between individuals for:
o Food
o Space
o Water
o Light
o Mates
There are 2 types of competition:
1. Interspecific competition
- Occurs between members of DIFFERENT species
o Ex: Between owls and hawks
o EX: Between coyotes and wolves
2. Intraspecific competition
- Occurs between members of the SAME species for space, food and mates
- This is more intense competition
o Ex: Between caribou for caribou moss or mates
o Ex: Between puffins for nesting spots
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There are also symbiotic relationships to consider:
1. Parasitism
- A symbiotic relationship in which one organism (the parasite) benefits and the other
(the host) is generally harmed.
Ex: fleas and dogs
2. Commensalism
- An association between two organisms in which one benefits and the other derives
neither benefit nor harm.
Ex: barnacles on a scallop shell
3. Mutualism
- a relationship between two species of organisms in which both benefit from the
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association
Ex: Fungus and algae of a lichen
Ex: clown fish and sea anemone
Food Chains and Food Webs
TEXT: - p. 34-35 (food webs/chains)
As we have already learned, every organism in an ecosystem provides energy for other
organisms as each lives in its own habitat and niche.
Food Chain
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The step by step sequence of who eats who in an ecosystem
The arrows point in the direction of energy flow (that is – towards the eater)
The owls would decrease because there would be no mice to eat
The grasshoppers would increase because there would be no predators.
The grass would decrease because all the grasshoppers would
eat all the grass.
– They have many food/prey items to depend on. That way, if something happens to one
species there are others to take their place.
So to clarify: Each organism is involved in many food chains that interlock with each other to
form a feeding relationship called a Food Web.
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Biodiversity
The number of species in an ecosystem
The most stable ecosystems are those with the greatest biodiversity. They have such
complex and well developed food webs that the reduction in numbers or the complete removal
of one species may have only a small effect on the overall food web.
In this way biodiversity is KEY to the success of all ecosystems!
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The Carbon Cycle and the Oxygen Cycle
TEXT: - p. 62-65 (carbon cycle)
- p. 641-642 (global warming)
Carbon is the key element for living things.
The earth is a closed system  Matter never leaves or enters our planet!
Therefore: every carbon atom is recycled time and time again into new life forms.
Complimentary to the carbon cycle is the oxygen cycle
Example:
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Digestion breaks down food molecules into simple molecules and our bodies reuse
them to build the complex molecules that our bodies need.
Decomposers break down dead organic matter and return the small molecules into
the soil and water where they can be utilized by other living things.
The Greenhouse Effect and The Significance of Global Warming
The greenhouse effect is a normal and necessary part of our existence on earth and without it
the planet would be too cold to inhabit. However, global warming is our own doing as we are
enhancing or increasing the greenhouse effect.
Human activities are leading to an increase in the amount of carbon dioxide released from
storage:
Burning fossil fuels
AND
Clearing land
As a result, the amount of carbon dioxide in our atmosphere is also increasing. This increases
what we call greenhouse gases in our atmosphere which acts as a blanket around the earth.
These greenhouse gases insulate the earth and are causing the earth’s temperatures to
increase. This is called global warming or climate change.
THe Nitrogen Cycle
TEXT: - p. 66-67 (nitrogen cycle)
- p. 127 (eutrophication)
Nitrogen is required:
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By cells to make proteins
Required for the synthesis of DNA (material of heredity)
It is cycled through ecosystems, soil and the atmosphere in the Nitrogen Cycle.
The movement of nitrogen through the ecosystems, the soil, and the atmosphere is called the
nitrogen cycle. In order for nitrogen to be useful to organisms, it must be available as a
nitrate ion (NO3-). Atmospheric nitrogen is converted into nitrates by the process of
nitrogen fixation, or nitrification either by lightning or by bacteria in the soil.
Role of Decomposers
Organisms produce waste and eventually die. Decomposers break down the organic
compounds in the decaying material into ammonia, which reacts with hydrogen ions to produce
ammonium, which, in turn undergo nitrification to give nitrates.
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Nitrification:a biological process during which nitrifying bacteria convert ammonia and
ammonium into nitrites then into nitrate.
Denitrification : a biological process during which denitrifying bacteria convert nitrates back into
nitrogen gas and release it back into the atmosphere
Succession
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Because communities are dynamic the numbers and types of organism can change
over time.
As populations interact they change the abiotic environment which in turn
influences the biotic environment.
Other species gradually move in and take over and form a new community.
Ecological Succession
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This process of successive change in species composition over time.
There are 2 types:
o Primary (1) – The development of a first time community in an area.
 Areas left bare by glaciers (rocks and gravel)
 After a volcanic eruption
Growth by prokaryotes, and then eukaryotes such as lichens gradually break
down the rock to form soil. It is generally much slower than secondary
succession and it can take up to 1000 years to produce enough soil to support
the first grasses.
o Secondary (2) – the redevelopment of a previously existing community after
a disturbance.
 After forest fires
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After clear cutting
After flooding
In Newfoundland and Labrador many disturbance events occur and
secondary succession happens repeatedly in a variety of locations.
Climax Community
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A self perpetuating community in which populations remain stable and exist in
balance with each other and the physical environment indicating that succession has
come to an end.
The Effect of Pesticides on Ecosystems
TEXT: - p. 57 (bald eagle)
- p. 52 (pesticides)
Pest
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An organism that is harmful or inconvenient to people
Pesticide
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Chemicals designed to kill pests
Humans have been using pesticides throughout history.
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In 500 BC sulfur was used to repel insects
15th century, arsenic, lead and mercury were used on crops as insecticides (it was
discovered later how harmful these heavy metals were and their use was stopped!)
Toxins produced by plants were popular:
o nicotine sulphate from tobacco plants
o chrysanthemum
o roots of legumes
Over the years 1000s of pesticides have been developed and 500 are registered for
use in Canada.
2.3 million tones are used each year worldwide for:
o Agriculture
o Shampoos
o Carpets
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Unit 1: Sustainability of Ecosystems
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o Mattresses
o Paints
o Wax on produce
A Special Case: DDT
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in 1939, DDT was developed as a potent insecticide
DDT is soluble in fat and not soluble in water.
As a result DDT accumulates in the fatty tissue of organisms and can be transferred
up the food chain.
While organisms low in the food chain may contain small amounts of this toxin,
organisms at higher trophic levels can build up high concentrations of DDT in their
bodies.
This process is called Bioamplification
In 1971 DDT was banned in Canada.
However, migratory birds and fish may still bring DDT to Canada from other
developing countries where it is still being used (where malaria is prevalent).
Result: The Bald Eagle
o High amounts of DDT result in soft eggshells which reduce the survival of
offspring.
Similarly is Bioaccumulation – the more toxin you ingest the more that builds up in your body.
Solution: Water soluble pesticides have been developed that are more easily flushed out of the
body through urine and sweat.
Complication:
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They are easily washed away by rain and have to be applied more often.
They are not species specific because they affect many organisms the same way.
Impact of External Factors on Biomes
TEXT: - p.116-117 acid rain
- p. 132-135 water pollution
- p. 81-82 pesticides (tent caterpillar)
- p. 72-73 deforestation
- p. 42-44 exotic species
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- p. 20-21 wolves
- p. 10-13 frogs
- p. 112-113 potatoes
- p. 140-142 Great Lakes
- Science 2200 STSE 1-6 pine marten
Short term stress
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a change from which the ecosystem can more easily recover from and adjust to.
o seasonal peaks in temperature
o seasonal extremes in water supply
o sudden but limited human impact
Long term change
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a change from which the ecosystem cannot easily recover from or adjust to.
o Climate change
o Permanent human influence
o Infestation by flora and fauna
Activity 1.7: Fishbone Diagram - Impact of External Factors on Biomes
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Read each of the selections in the
text and briefly identify the change
that has occurred and state weather
it is long term change or short term stress
Record your findings on the worksheet.
Homework: Finish worksheet.
Fertilizers, Irrigation and Soil Quality
TEXT: - p. 70-71 (agriculture and nutrient cycles)
Fertilizers
Crops deplete soil of nutrients (nitrates and phosphates)
Fertilizers restore nutrients and increase crop production.
How Fertilizers Work
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Bacteria in the soil convert nitrogen in the fertilizer into nitrates that can be used by plants.
Remember the Nitrogen cycle?
Problem:
Nitrates can increase nitric acid in the soil resulting in a drop in pH which can:
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Affect decomposing bacteria
Affect other soil organisms
Affect growth conditions of most commercial crops
This problem is only exacerbated (made worse) by acid rain and snow. Oops!
Fertilizers and Ecosystems
Spring run-off and irrigation carries decaying matter and fertilizer rich soil into streams and
lakes.
Result: Algal Bloom
And when the algae die, bacteria use oxygen to decompose them causing oxygen levels to drop
rapidly so fish and other animals begin to die.
Sound Familiar? Eutrophication!
For these reasons the improper use of both natural and synthetic fertilizers can have a
detrimental effect on an ecosystem.
Homework: Qs p. 71 #1-8
Distribution of Canadian Biomes
TEXT: - p. 88-93 (Canadian biomes)
Biomes are large ecosystems and their distribution is largely based on abiotic factors such as:
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Radiant energy (sunshine)
Precipitation
Nutrient levels
Elevation
Because similar abiotic conditions exist in different areas around the world, biome distribution
can be global.
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Earlier in this unit we learned that abiotic factors determine biotic factors.
Therefore: the same biome in different parts of the world may contain similar species because
of similar abiotic factors such as climate, water conditions, geographical features.
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Ex: all deserts will have cacti
Ex: salmon can be farmed (aquaculture) in many parts of the world including:
o Off the south coast of Newfoundland
o The North Sea (Norway, Scotland)
o South America (Chili)
Canada’s Biomes
1.
2.
3.
4.
Tundra
Boreal forest
Temperate deciduous forest
Grassland
Activity 1.9: Canadian Biomes Extension Activity
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Use your text to complete the worksheet
Abiotic factors are key in determining the distribution of the biomes and the impact of
external factors on these abiotic factors will affect and change biome distribution.
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Ex: the tundra is vanishing due to global warming and disrupted nutrient cycles.
Homework: Finish Biome Worksheet
Case Studies are added to the end of this unit and will be completed in class.