Introduction to EcologySpheres of the Earth
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We will now examine the biosphere and its
parts. This can be divided into large areas
called biomes. In Canada there are four main
terrestrial biomes.
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Biome: A major terrestrial area which contains
specific plants and animals and has a specific
climate. Canadian Biomes include the Tundra
(arctic), Boreal Coniferous Forest, Temperate
Deciduous Forest, rainforest (BC), and
Grasslands.
3
Ecosystem: A community of living organisms
(biotic) together with non-living factors
(abiotic) with which it interacts.
Community: A group of different species that
live together in a particular place.
Population: A group of animals or plants of the
same species.
Individual: One member of a specific
population.
4
Ecosystems can be divided according to their
type:
A natural ecosystem is one that occurs in
nature. Immigration and emigration, along
with births and deaths affect population size.
For e.g., forest, pond, stream.
An artificial ecosystem is one which is
controlled so that immigration, emigration,
birth and death rate do not affect population
size to a large extent. Eg., zoo.
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Ecosystems can also be divided according to
where they occur:
Terrestrial ecosystems exist on land i.e. desert,
tropical rain forest.
Aquatic ecosystems exist in a body of water i.e.
ocean, pond or stream.
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Learning about Ecosystems:
Ecosystems can be divided many different
ways:
Producers are organisms that can make their
own food, usually through a process known as
photosynthesis. They are also known as
autotrophs (self feeders).
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Consumers are organisms that must consume
their food or energy source. They are often
called heterotrophs (other feeders).
Consumers can be further divided according to
what they eat:
Herbivore: An organism consuming mainly
plants
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Carnivore: An organism consuming mainly
other animals
Omnivore: An organism consuming both plants
and animals.
Scavenger: An organism which feeds on dead
animals matter
Decomposer: An organism which breaks down
the bodies of dead organisms or the waste
products of organisms.
Together these organisms above make up a
food chain or food web.
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Food Chain: Shows the feeding relationships or
sequences of various organisms.
Food Web: A series of food chains
interconnected with each other. This gives a
more accurate picture of an actual ecosystem.
If the numbers of any part of a food web
increase of decrease, the entire web will be
affected.
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A Food Web
Fox
Hawks/Owls
Snakes
Frogs
Spiders
Insectivorous Birds
Seed eating birds
Rabbits
Mice
Insects
Plants
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Each level within a food web or chain is
referred to as a trophic level. The trophic level
is the feeding level of an organism in the chain
or web.
All food webs begin with a producer which
makes its own food by photosynthesis.
Producers are the first trophic level.
The other members of a food web can be
identified as primary consumers, secondary
consumers and tertiary consumers. The
tertiary consumer is also often known as the
top carnivore (this animal may actually be an
omnivore). The top carnivore may have no
natural predators, except maybe people.
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A Terrestrial Food Web
Mountain Lion
Tertiary
Consumer
Foxes
Secondary
Snakes
Owls
Consumer
Seed-eating Birds
Rabbits
Primary
Deer
Mice
Squirrels
Vegetables
Trees
Consumer
Producers
Grass
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An Aquatic Food Web
Hawks
Humans
Land Mammals
Fish
Small Birds
Shrimp
Worms
Clams
Algae
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A Typical Aquatic Food Web
Answer the following based on the aquatic food web provided:
1. What do you think the producer is in our food web? Explain.
2. Name two primary consumers.
3. What two organisms could be considered the top carnivores?
4. Name a secondary consumer?
5. What do you think would happen if all the fish disappeared from this ecosystem?
6. The organisms listed are all biotic components of an ecosystem. Name two abiotic
components of this ecosystem.
7. How would scavengers or decomposers fit into this food web?
8. Name one herbivore and two carnivores.
9. Are there any organisms in our food web which might be considered an omnivore?
Explain.
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A Review of Food Webs
Wolf
Fox
Hawk
Mice
Snake
Grasshoppers
Owl
Rabbit
Deer
Grass/weeds/seeds
1.
2.
3.
4.
5.
6.
7.
Shrubs
What are the top carnivores in this web?
Name two producers in this web.
What type of consumer is the owl?
Name the herbivores in this web.
What is the process by which most producers make their own food?
What is another term for a primary consumer?
What is another term for a producer?
Circle the correct answer:
1. There are usually more or less organisms at the bottom of the food web compared to
the top.
2. Organisms at the top are usually smaller or bigger in size.
3. Producers or consumers are usually at the bottom of a food web.
4. Life cycles are usually longer or shorter for smaller organisms.
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Predator-Prey Relationships
An organism’s habitat is the place where it
lives. It may be a pond, the ocean, a forest or a
desert.
Organisms also have a niche. This can be
described as an organism’s “job” or role in the
habitat. A beaver’s niche is to build dams.
To be a predator or prey may also be part of an
organism’s niche.
Predator-Prey relationships usually involve the
hunter (predator) and the hunted (prey). They
may occur in terrestrial or in aquatic habitats.
The top carnivore is usually a strong predator
i.e. a great white shark, a lion, a tiger, a grizzly
bear.
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18
19
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Although some of the prey in the relationship
die to be eaten by the predators, this
relationship is necessary to keep the entire
ecosystem balanced. If the top predator is
taken out of a food web or ecosystem, this will
affect nearly every other part of the ecosystem.
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Snowshoe Hare and Canada Lynx
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Predator-Prey Relationships – The
Snowshoe Hare and the Canada Lynx
Problem: How do a predator and its prey control each other’s
population?
Materials: Graph paper and pencil
Procedure:
1. On the graph paper, plot the information concerning the number of Snowshoe Hare.
Locate the population on the y-axis and the years on the x-axis. Graph this population.
2. On the same graph, plot the data for the Canada Lynx. Be sure to differentiate between
your two graph lines.
Observations: (11 Comm.)
1. What length of time is represented on the graph? (1)
2. During this time, what is the largest population of the lynx? Of the Hare? (2)
3. Why might the hare population increase? Why might it decrease?(4)
4. Why might the lynx population increase? Why might it decrease?(4)
Questions:
1. Why do changes in the lynx population follow the changes in the hare population?(2)
2. How can both predator and prey be said to control each other’s population?(2)
3. If there were no lynx controlling the population, what would eventually happen to the
population of snowshoe hares?(2)
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Populations of Hare x 1000
Year
Population x 1000
1845
1850
1855
1860
1865
1870
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
1930
1935
12
76
68
8
152
16
84
12
120
60
20
8
64
28
12
8
72
12
80
Populations of Lynx x 1000
Year
Population x 1000
1848
1853
1858
1863
1868
1873
1878
1883
1888
1893
1898
1903
1908
1913
1918
1923
1928
1933
1938
28
8
24
4
60
8
32
16
72
20
36
4
40
4
24
2
28
8
32
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Snowshoe Hare-Canada Lynx
You have a wonderful new job with the Canadian Ministry of Fish and Wildlife. One of your
first assignments is to address the drastic decline in snowshoe hare populations over the past four
years. Snowshoe hare survive the harsh Canadian winters by eating the sparse vegetation that
appears above the snow line. They have a very rapid rate of reproduction, enabling them to
undergo sudden bursts in population. Their major predator is the Canada lynx. The Canada lynx
is a predatory cat that survives solely by eating snowshoe hare. The lynx has a much slower rate
of reproduction than does the hare.
Among the many proposals that you have been asked to review is a proposal to save the hare by
drastically reducing the lynx population. While researching the potential effectiveness of this
plan, you come across an interesting study from the 1930's. The following data represents the
number of pelts brought into the Hudson Bay Trading Company over a 28 year period. The study
concludes that the numbers of pelts accurately mirrors the number of animals in the wild.
Data:
Time elapsed Snowshoe Hare
(years)
Pelts (thousands)
Canada Lynx Pelts
(hundreds)
0
20
10
2
55
15
4
65
55
6
95
60
8
55
20
10
5
15
12
15
10
14
50
60
16
75
60
18
20
10
20
25
5
22
50
25
24
70
40
26
30
25
28
15
5
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Procedure: (10 Marks Comm.)
Create a line graph showing how both the hare and lynx populations changed over this 28 year
period. Make sure to accurately label your axes and the lines you make. Years should be on your
x axis and the number of pelts on the y axis. Both populations should be reflected on the
same graph.
Analysis: (6 Marks T/I)
1. Describe the relationship between the lynx population and the hare population through
time. Does there appear to be any relationship between the changes in these populations?
(2)
2. Based on the information in this graph, should you approve the proposal to reduce the
lynx population? What is likely to happen if you do? What is likely to happen if you do
not? (4)
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Ecosystems: Limiting Factors
The healthiest ecosystems have a high degree
of biodiversity. This refers to the number of
different species in the ecosystem. An
ecosystem with a lot of diversity is able to deal
with changes more effectively.
Ecosystems, however, do have limits to the
number of organisms they can support. This is
referred to as carrying capacity and is
determined by the available resources like
space, food, water and other nutrients. These
are known as limiting factors. Other limiting
factors might include the number of predators
present or disease causing agents. An
ecosystem can briefly exceed its carrying
capacity but not for long.
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Nutrient Cycles
Nutrients are the basic raw materials from
which organisms manufacture everything
needed to grow and carry out life’s functions.
These nutrients are continuously recycled
through an ecosystem.
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Water Cycle:
The water cycle is the life story of a water
molecule. It begins in the clouds, falls as some
form of precipitation to the ground of into
bodies of water. With the help of the sun, it
eventually evaporates, forms clouds and
condenses, returning to earth as precipitation
once again.
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Carbon Cycle:
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The carbon cycle is a balance between two
processes: photosynthesis and cellular
respiration. Plants carry out photosynthesis to
make their food and in doing this they produce
oxygen which they put out into the air.
Animals breathe in this oxygen, use it to turn
our food into energy through cellular
respiration and as a result we produce carbon
dioxide which we put into the air for plants.
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Nitrogen Cycle:
Nitrogen serves as a fertilizer in the soil to help
plants grow. These plants and the animals eat
them eventually die. Decomposers, like
nitrogen fixing bacteria, feed off dead plant and
animal matter as well as the waste of animals,
and return this nitrogen back to the soil so it is
available to help a new generation of plants
grow.
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Ecological Pyramids
The information in a food chain may also be
shown in a pyramid. This pyramid may be a
pyramid of numbers, showing the numbers of
the organisms involved; a pyramid of energy
showing the amount of energy at each trophic
level; or a pyramid of biomass showing the
total mass of the organisms at each trophic
level. Ecological pyramid are similar to food
chains but give more information.
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A Pyramid of Numbers
Occasionally these may be turned upside down:
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A Pyramid of Energy
Energy is lost at each trophic level because the
organisms expend some energy to find food,
escape predators, find mates etc. As a general
rule, only 10% of the energy is passed onto the
next trophic level. This is called the ecological
rule of ten. Having less energy usually means
smaller numbers.
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Pyramid of Biomass
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Canadian Biomes
Biome: A collection of ecosystems that are similar to each other, usually in the type of plants and
animals they support. They also have a similar climate.
There are four main Canadian Biomes:
1.
The Tundra Biome:
 Low precipitation
 Permafrost below the soil
 Poor quality soil
 Shortest growing soil
 Mosses, wolverines, caribou, rapid flowering plants, arctic foxes
2. The Boreal Forest Biome:
 Precipitation 40 cm or more
 Cool, but no permafrost
 Acidic soil, some water
 Changeable weather
 Coniferous trees (with needles), seed eating birds, squirrels, deer, grey wolves
3. The Temperate Deciduous Forest Biome:
 Dominated by deciduous trees (lose their leaves)
 Found in Central and Eastern Canada
 Contains large, broad leaves that can photosynthesize easily
 Rich soils that support a variety of small shrubs and trees
 Deciduous trees, shrubs, ferns, shrews, mice, deer, black bears, woodpeckers, weasels,
wolves
4. The Grasslands Biome:
 Precipitation 27-75 cm
 Rich, fertile soil
 Longer growing season
 High Temperature
 Bison, mice, snakes, hawks, wolves
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Canadian Biomes
Biome: A collection of ecosystems that are
similar to each other, usually in the type of
plants and animals they support. They also
have a similar climate.
There are four main Canadian Biomes:
1.
The Tundra Biome:
 Low precipitation
 Permafrost below the soil
 Poor quality soil
 Shortest growing soil
 Mosses, wolverines, caribou, rapid
flowering plants, arctic foxes
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2.
The Boreal Forest Biome:
 Precipitation 40 cm or more
 Cool, but no permafrost
 Acidic soil, some water
 Changeable weather
 Coniferous trees (with needles), seed
eating birds, squirrels, deer, grey wolves
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3.
The Temperate Deciduous Forest
Biome:
 Dominated by deciduous trees (lose
their leaves)
 Found in Central and Eastern Canada
 Contains large, broad leaves that can
photosynthesize easily
 Rich soils that support a variety of small
shrubs and trees
 Deciduous trees, shrubs, ferns, shrews,
mice, deer, black bears, woodpeckers,
weasels, wolves
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4.
The Grasslands Biome:
 Precipitation 27-75 cm
 Rich, fertile soil
 Longer growing season
 High Temperature
 Bison, mice, snakes, hawks, wolves
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Biomes Questions
1. Define Biome.
2. List the four Canadian Biomes.
3. Which of the biomes occupies most of Canada?
4. Which of the biomes occupies most of Ontario?
5. Which two biomes are present in North America but not Canada?
6. Where in the United States would you find Tundra? Where in Canada?
7. Where in Canada would you find Grasslands?
8. Is there any Temperate Deciduous Forest in Canada? If so, where?
9. Why is the Tundra often called the cold/frozen dessert?
10. Is there any Tropical Rain Forest in Canada? In the U.S.?
11. Where is most Tropical Rain Forest found?
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Activity:
 In your group, divide a sheet of paper into four quarters.
 Label each quadrant with a Canadian Biome.
 In each quadrant place the proper abiotic factors and communities from
the list below
 For each quadrant, list what problems are currently facing that biome.
Abiotic Factors
Communities
 Precipitation from 25-75 cm/year
 Mosses and lichens
 Low Precipitation
 Wolves (can use twice)
 Fertile soil
 Voles, mice
 Cool but no permafrost
 Snowshoe hares
 Changeable weather
 Deer (can use twice)
 Longer growing season than
 Arctic foxes
some forests (can use twice)
 Tress squirrels
 Higher temperature than some
 Shrews, mice
forests (can use twice)
 Snakes
 Permafrost layer below soil
 Weasels
 Poor soil quality
 Seed-eating birds
 Rich, fertile soil
 Wolverines
 Precipitation up to 100 cm/year
 Tree and ground squirrels
 Acidic soil with some water
 Bison
 Precipitation over 40 cm/year
 Grey wolves
 Coldest temperatures
 Lemmings
 Shortest growing seasons
 Caribou
 Coniferous trees
 Hawks
 Woodpeckers
 Grasshoppers
 Black bears
 Deciduous trees
 Rapid flowering plants
 Grasses
 Many shrubs and ferns
 Many insects
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