The Living World:
Ecosystems (Chapter 10)
1
Ecosystem – A community of living organisms
interacting with one another and
with the nonliving components of
the environment they inhabit.
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Levels of Ecological Organization
Level 1
Individual ( A Moose)
Level 2
Population (Herd of Moose)
Level 3
Community: (Herd + Birds +
Squirrels + etc
Level 4
Ecosystem : Living + nonliving
components in the environment
Examples of Ecosystems:
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Forest
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Lake
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Aquarium
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Island
1 .1
Interactions within Ecosystems
Trophic Relationships The feeding
connections among the living organisms in
an ecosystem (a food chain)
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Simple food “chain”
More realistic food “web”
Producers – autotrophic (self nourish) organisms
with the ability to create organic matter from
inorganic matter in an ecosystem through
photosynthesis. Plants use sunlight to make sugars
for energy.
Plants
Phytoplankton
(algae)
Inorganic vs. organic matter
Inorganic
matter
Matter that is not necessarily produced by
living organisms. (e.g. Water, mineral salts,
carbon dioxide)
Organic
matter
Matter that enters into the composition of
living organisms and that is usually created
by them.
(e.g. proteins, carbohydrates, fats)
Consumers – heterotrophic (other nourishment)
organisms that feed on other living organisms and/or
their products such as eggs, fruit etc.
Consumers
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First order (or primary) consumers: feed on
producers (eg: a deer eats grass, birds eat seeds).
They are herbivores.
Second order consumers: feed on first order
consumers (eg: a wolf eats a deer, a cat eats a
bird). They are carnivores.
Third order consumers: feed on second order
consumers
Fourth order consumers: feed on third order
consumers etc. etc.
Omnivores:
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Consumers that eat several orders at once.
(eg: bears eat berries and fish, humans eat
grain and meat).
Decomposers – organisms that feed on the waste
and remains of other living organisms.
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Decomposers are
detritivores which are
heterotrophs that can
be eaten by
consumers
Feed on detritus
which is dead organic
matter such as fallen
leaves, dead wood,
animal remains, etc
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Examples are:
worms, some
bacteria, certain
insects such as the
sow bug
Trophic Network – Food Web
1 .2
Ecosystem Dynamics
Material and Energy Flow – the exchange of
matter and energy between the living
organisms in an ecosystem and between those
organisms and their environment.
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Law of conservation of Mass –
nothing is loss and
nothing is created;
Matter is transformed
Material Flow and Chemical Recycling
Chemical recycling – is a natural phenomenon
by which decomposers make inorganic
matter available in an ecosystem by
breaking down organic matter.
Chemical Recycling
Decomposers
Detritus
Consumers
Producers
Environment
Flow of inorganic matter
Flow of organic matter
Energy Flow: the sun is the main
source of energy for ecosystems
Thermal energy lost in the environment
Radiation energy
Producer
Primary
Secondary
Consumer
Consumer
1 .3
Biomass and Primary Productivity in
Ecosystems
Biomass – the total mass of organic matter in
an ecosystem at any given time.
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Primary productivity of an ecosystem is the amount
of new biomass generated by its producers
Factors that affect primary productivity are:
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Light (radiation energy) from the sun
Amount of water (necessary for photosynthesis)
Essential nutrients (carbon, nitrogen, phosphorus,
and potassium)
Temperature – weather promotes growth of
producers
2
Disturbances
A disturbance is an event that damages an ecosystem.
It can lead to the elimination of organisms and alter
the availability of resources.
E.g. flooding, storms, oil spills, volcanic eruptions
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2.1
Natural Disturbances
Events triggered by environmental
phenomena rather than humans but can be
very damaging nonetheless. (storm
churning waters = surface + subsurface
waters to mix)
E.g. volcanic eruptions, drought, flood,
forest fires, frost, freeze rain & heat waves
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2.2
Human Disturbances
Humans and their actions are a major threat
to ecosystems from individual acts like
littering to large scale projects.
E.g. logging, mining, oil spills, housing
projects, industries, pollution, etc.
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2.3
Ecological Succession
Ecological succession – the series of changes
that occur in an ecosystem after a
disturbance and that continue until the
balance of the ecosystem is restored.
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A forest recovering after acid rain
2.4
Ecological Footprints
Ecological footprints are estimates of the surface
area individual humans or populations require
to obtain the resources for satisfying all their
needs and to ensure the disposal of their
waste.
Ecological
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Footprint
=
Land &
water
occupied
Land &
Land &
water used
+
+ water used
to produce
to dispose
goods
of waste
Ecological Carrying Capacity
10
9
8
7
6
5
4
3
2
1
0
Ecological Footprints
World
Canada
Japan
China
3
Ecotoxicology is the study
of the ecological
consequences of polluting
the environment with
various substances and
radiation, released by
human activity.
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3.1
Contaminants – is any type of substance or
radiation that is likely to cause harm to one or
more ecosystems.
Class of
contaminants
Inorganic
Organic
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Examples
Lead, arsenic, mercury, nitrogen
oxides, phosphorus
Insecticides, pesticides, benzene,
polychlorinated biphenyls (PCBs)
Microbial
Viruses and harmful bacteria
Radioactive
Uranium, plutonium, radon
Toxicity
Toxicity of each contaminant depends of the
following three factors:
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Concentration – more concentrated higher the risk
Type of organism it comes in contact with
Length of exposure
Toxicity threshold – the level of concentration
above which a contaminant causes one or
more harmful effects in an organism
LD – indicator used to determine toxicity
dose that is lethal to 50% of individuals
50
3.2
Bioaccumulation and
Bioconcentration of Contaminants
Bioaccumulation –
the tendency among
certain contaminants
to accumulate over
time in the tissues of
living organisms.
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Bioconcentration
– a phenomenon
by which the
concentration of
a contaminant in
the tissues of
living organisms
tends to increase
with each trophic
level.
4
Biotechnology
Biodegradation – the breaking down of
organic matter into inorganic matter by
microorganisms
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Bioremediation – a biotechnology for
cleaning up a polluted site, using
microorganisms that decompose the
contaminants.
Phytoremediation – a biotechnology that uses
plants or algae to eliminate contaminants
from a site.
Wastewater Treatment
Wastewater – water that is discharged after
household or industrial use and that is polluted as
a result of human activities.
Wastewater can contain:
 Sand or other particles
 Pathogens
 Nutrients that stimulate the excessive growth of
algae
 Chemicals
Two main methods for treating wastewater are:
Septic Tanks and Wastewater Treatment plants
Checkup
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Pg 342 # 1-15, A and C
Pg 342 # 1-26, A - C
Pg 342 # 18-23, B
ST and AST
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Eco-sketch Complex Task (ST & AST)
Pg 323 – Vermicomposting from cafeteria
(optional)
References
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Observatory the Environment – Cyr,
Forget, Verreault – 2009, ERPI
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