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Putting it all together
What is an ecosystem?
O Ecosystem – all of the living organisms that
share a region and interact with each other
and their non-living environment. Can differ
in size and features.
O Abiotic factors – non living components of
an ecosystem
O Biotic Factors – living organisms and their
products that occupy an ecosystem
3 Types of Ecology
O Ecosystem Ecology -
integrated study of
all living and nonliving factors that
operate within an
framework. Includes
food webs,
Community Ecology
O studies how
populations of
different species
interact within a given
ecosystem. Includes
Competition, Predation
Mutualism (Symbiosis,
Commensalism and
Parasitism), feeding
relationships and
ecological pyramids
Population Ecology
O deals with the
dynamics of species
populations and how
these populations
interact with the
environment. It is the
study of how the
population sizes of
species groups change
over time and space.
Population ecology
O A population is the number of individuals of
a single species that reside in a given area.
O limiting factors, tolerance and optimal
ranges and carrying capacities of a given
An integrated approach
• Abiotic and biotic
• Cycles/food webs
• Interactions between
• Competition,
predation, mutualism
• Growth of single
• Carrying capacity,
limiting factors, range
What is the value of
O Why do we need
O What value are they
to us when we can
grow our own
Cultural value of ecosystems
O Cultural services –
aesthetic and
spiritual experiences
we receive when we
interact with natural
surroundings. Eg.
O Ecosystem Products
– ecosystems
produce many of the
things we use or
consume every day.
These include food,
medicine, water and
O Regulatory and
protective services –
ecosystems protect
us from natural
threats (eg. Plants
protect soil from
erosion, filter air,
produce oxygen)
Total services provided
The value of ecosystems is
greatly reduced when
ecosystems are thrown off
Equilibrium and Change
O Most natural ecosystems are in a state of
equilibrium – relatively stable biotic and abiotic
O Energy flows through food webs, nutrients are
recycled, photosynthesis and cellular respiration
are balanced
O On a small scale, most ecosystems are in
constant change. E.g. a fire breaks out, a tree
falls etc.
Ecological Succession
O Ecological succession – process of
establishing and replacing a community
following a disturbance.
O Primary succession – occurs on bare rock
where there was no previous life
O Secondary succession – follows a
disturbance that disrupts but does not
destroy the community.
Ecological Succession
O Benefits of succession – mechanism by
which ecosystems maintain their long-term
O Not all disturbances can be repaired through
natural succession. Human disturbances
often have to repair ecosystems through
processes that support natural succession.
Textbook question
O A Krakatoa eruption destroyed life and left
behind volcanic ash. A large chemical spill
can also destroy life. How would succession
be very different following these two events?
What is one way to ensure
stability of ecosystems?
O variety of life found in an area
O Measured by counting the number of species in
a specific habitat or ecosystem. This
measurement of species is called species
O In general, species richness tends to be higher
close to the equator
O Tropical rainforests have the highest biodiversity
of any ecosystem.
Species at risk
O Many of the world’s
species are dying out
or going extinct.
Their habitats are
destroyed through
deforestation, urban
and agricultural
expansion, pollution
and climate change.
Extinction events
O Extinction is a natural process. Over
thousands of millions of years, some
species become extinct while new species
O There have been at least 5 major extinction
events in the past billion years.
Extinction events are usually caused
by a catastrophic event such as an
asteroid impact or massive volcanic
eruption. Between such rare events,
extinction rates are low.
Unfortunately, human activity has
greatly increased the rate of
Species at risk
O Species do not have to be driven to
extinction for there to be ecological
O In Canada, the status of species is
monitored by the Committee on the Status
of Endangered Wildlife in Canada.
Species at risk
O Extirpated – no longer exist in their native area but
are still alive elsewhere (eg. Atlantic walrus)
O Endangered – species are in imminent danger of
going extinct or becoming extirpated.
O Threatened – Species likely to become endangered if
current trends continue (ie. humpback whale)
O Special concern – may become threatened or
endangered because of a combination of factors.
Special concern
Population ecology
What about us?