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Unit D – Living Systems
Chapter 1
The biosphere of Life
Section 1.6
The Recycling of Matter
Human impact on the natural
environment

In the last section, we saw the impact that
human activities can have on the cycling of
matter
– deforestation
– burning of fossil fuels
– industry
Human impacts

The human impact on abiotic factors
includes:
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Polluting of water sources ( H2O)
Over-reliance on fertilizers ( N-compounds)
Clear-cutting ( O2,  CO2)
Burning of fossil fuels ( O2,  CO2)
Use of CFCs ( O3,  UV radiation)
Human impacts
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Now we will examine the human impact on biotic factors
An ecosystem is considered to be healthy if it is free of
stresses such as
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–
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pollution
a loss of vegetation
disruption of water flow
introduction of new species
An ecosystem also needs to be able to recover from
disturbances
Humans have an effect on an ecosystem by
– causing stress to the ecosystem
– interfering with the ecosystem’s ability to recover from stress

The Three Gorges Dam is
a hydroelectric dam that
spans the Yangtze River
in China.
Habitat fragmentation

habitat fragmentation
– breaking a continuous habitat into smaller,
separate habitats
– fragmentation can occur by
 roads
 natural gas pipelines
 power lines
 clear cutting
Impact of habitat fragmentation
interspecific relationships are affected
because the two species may be physically
isolated
 cleared areas may help support one
species, which causes a shift in the balance
in the ecosystem
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Impact of habitat fragmentation - Example

In Northern Alberta, a lot of boreal
(evergreen) forests have been
fragmented by roads built by oil and
gas companies
– The ideal habitat for woodland caribou is
the boreal forests
– In comparison, moose thrive more in
cleared areas
– As more roads come in, moose
populations increase
– This increases the populations of predators
like wolves
– Wolves prey on caribou, threatening their
survival
– Caribou are now on the endangered
species list
Planet earth Caribou and Wolves (Great
Plaines 14:35)
Habitat destruction

Habitat destruction
– the permanent alteration of a habitat
– clear-cutting is the most significant example of
habitat destruction
– when a habitat is destroyed, a large number of
species are affected
 habitat destruction is the leading cause of species
endangerment and extinction
Species at risk
There are five categories for species whose
survival is at risk
 Categories range from vulnerable to
extinct, depending on how serious the
threat is to their survival

Species at risk in Alberta
Vulnerable
1.
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species likely to become threatened
in the future
e.g. wolverine
Threatened
2.
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species likely to become endangered
if the factors aren’t reversed
e.g. peregrine falcon
Endangered
3.
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species is threatened by imminent
extinction throughout the area
e.g. woodland caribou, swift fox
Species at risk in Alberta
4.
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5.
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Extirpated
species no longer exists in the area, but still
exists elsewhere
e.g. black-footed ferret
Extinct
species no longer exists anywhere
e.g. Banff longnose dace
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species was only found in Banff National Park,
in a marsh into which the Cave and Basin
Hotsprings drain
there is no estimate as to the past size of the
population
population was killed-off by
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the introduction of tropical fishes,
leakage of chlorine from a swimming pool into
the marsh,
construction of a beaver dam
Extinct Species
Tasmanian Tiger
Mass extinction

Since the Industrial Revolution began in the
1700s
– 10-20% of the Earth’s species have become extinct
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if the current extinction rates continue,
– we could see a loss of 50% of our biodiversity by
2100
– that means half the Earth’s species will be extinct
– referred to as a mass extinction

mass extinctions
– have only occurred 5 or 6 times in Earth’s history (600
million years)
– have previously been due to natural phenomena such
as meteors colliding with Earth
Loss of biodiversity

biodiversity
– the variety of ecosystems, species, and genetic
diversity in an area
– typically, an ecosystem with more species and
genetic diversity is better able to adapt to
change
– as species become extinct, or genetically
limited, the entire ecosystem is affected
Genetic diversity

One example of a loss in genetic diversity
in a population is the Labrador Retriever in
North America
– due to overly selective breeding practices, the
gene pool in labs has been dramatically cut
down
– as a result, labs are more susceptible to hip
problems and disease
– the average life expectancy of a lab has
dropped from 15 years to 10-12 years
Invasive species
an invasion refers to large-scale onset of
something harmful
 invasive species

– a new species is introduced into an ecosystem
– the species thrives, and expands in population
– species takes over and threatens the area’s
biodiversity
Introduction of invasive species
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new species are introduced by human action
– could be unintentional
 e.g. a few members of one species stow away on a ship
traveling to another part of the world
 organisms can hitch a ride in
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vehicles (ships, planes, trains, trucks, etc)
shipping containers, mail freight & packing materials
travelers’ luggage
agricultural produce
Pythons invasive species
– could be intentional
 attempt to expand biodiversity (e.g. give a region new food
options)
 biological control
– governments introduce new species to try to control other
damaging species
Past attempts at biological control
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in Canada, a small insect called a
weevil destroys canola and other crops
– to combat the weevil invasion, two species
of wasps were introduced one of which
attacks adult weevils, and the other which
feeds on the larvae
– both wasp species are parasitic but do not
sting humans
– the wasps have successfully suppressed the
weevil populations in Europe, but have
only had limited success in North America
Past attempts at biological control

in Australia in the 1930s, a population of scarab beetles
was destroying sugar cane crops
– the Australian government purchased 100 cane toads from
Hawaii, which they believed would eat the sugarcane beetles
– unfortunately, the Aussies didn’t do enough research, and found
the cane toads didn’t often come in contact with the beetles, let
alone eat them
– compounding the problem is the fact that cane toads are
poisonous, posing a danger to children, pets and wild animals.
– there are no predators in Australia that feed on the poisonous
toads, and as a result, cane toads are considered a pest far more
serious than the original scarab beetle population – oops!
Effect of invasive species
A native species is one that was found naturally
in that ecosystem
 How does the introduction of a new species
threaten the survival of native species?

– kill native species
– compete with native species for food and space
– spread new diseases and parasites to native species
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Typically, new species are able to thrive because
they have limited threats of being preyed upon
– no natural predators exist for a new species
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At
Atlantic vs Wild Chinook
Economy vs. Ecology
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Our economic system provides
us with
– employment
– means to buy goods and
services

Our ecological system provides
us with
– clean air
– clean water
– food
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Though as humans we rely on
both systems to maintain our
quality of life, the goals of the
two systems are often in
opposition
Economy vs. Ecology
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Timeframe
– ecosystems take thousands to millions of years to become
established and balanced
– the average business makes significant changes every three
months
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Physical environment
– ecosystems are inextricably tied to their physical surroundings
– for a business, the physical surroundings are not as important as
cheap labour and low transportation costs
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Measure of success
– an ecosystem is considered successful if it shows stability &
balance
– a business is considered successful if it shows profit, usually at the
expense of another business
Practice problems
Page 456 #48
 Page 458 #50-52
 Page 462 #1, 4
 INVASIVE SPECIES --- Cane Toad Movie
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