ENVI 6 community ecology FINAL

1. COMMUNITY ECOLOGY
Chapter 6

2. COMMUNITY ECOLOGY
The division of ecology that
deals with the study of the
interactions among species and
interactions with the abiotic
environment
Composed of all population of
a given area
A group of populations
interacting with one another
within the same environment.

3. RELATIONSHIP AMONG ORGANISMS
Symbiotic Relationship
 two entire different organisms live in close association that
benefits at least one of them.
Kinds of Symbiotic Relationship
Mutualism
Commensalism
Parasitism

4. MUTUALISM
Both organisms are
benefited and obligatory
Double positive
interaction (+,+)
Lichens consists of algae and
fungi.
Algae produce food.
Fungi provide water and
habitat.

5. PROTOCOOPERATION
Both organisms are benefited
but not obligatory
Double positive interaction
(+,+)
A sea anemone makes an ideal
home for a clownfish.
A clownfish can help an anemone
catch its prey by luring other fish
toward over so that the anemone
can catch them.

6. COMMENSALISM
One organism benefits while the other is neither benefited nor
destroyed
Positive-neutral interaction (+,0)

7. PARASITISM
One organism (parasite) benefits and the other (host) is harmed
Positive-negative interaction (+,-)

8. AMENSALISM
One organism is
inhabited or destroyed
and the other is not
affected
Negative-neutral
interaction (-,0)
Algal bloom can lead to the
death of fishes, however
the algae do not benefit
from these deaths.

9. PREDATION
Predator species
benefits while prey
species is harmed
One organism benefits
at the expense of
another
Positive-negative
interaction (+,-)

10. COMPETITION
Both organisms are affected
Organisms struggle with each other to obtain limited resources
Can be interspecific or intraspecific
Negative-negative interaction (-,-)
Gause’s Principle (Interspecific Competition)
If two populations of organisms occupy the same ecological niche,
one of the populations will be eliminated.

11. INTERSPECIFIC COMPETITION
competition
between different
species fight for
resources within an
ecosystem

12. INTRASPECIFIC COMPETITION
competition
between individual
members of the
same species fight
for resources within
an ecosystem
These wolves are
competing for food
and for social
dominance.

13. TYPES OF TWO-SPECIES INTERACTION
INTERACTION SPECIES A SPECIES B DESCRIPTION
Mutualism + + Both benefited and obligatory
Protocooperation + + Both benefited and not obligatory
Commensalism + O Species A is benefited while species B is
Parasitism + – Species A is benefited while species B is harmed
Amensalism – O Species A is harmed while species B is unaffected
Competition
– – Both are affected
Predation + – Species A feeds on species B.

14. HOW ECOSYSTEMS CHANGE
Ecological Succession

15. ECOLOGICAL SUCCESSION
It is a gradual process of change and replacement of the types
of species in a community
In nature, the process of ecological succession may take
hundreds or thousands of years.
Each new community that arises often makes it harder for the
previous community to survive.

16. PRIMARY SUCCESSION
It is a type of succession that occurs on a surface where no
ecosystem existed before.
Primary succession can occur on rocks, cliffs, and sand dunes.
Primary succession is much slower than secondary succession
because primary succession begins where there is no soil.
It can take several hundred to several thousand years to produce
fertile soil naturally.

17. SECONDARY SUCCESSION
It is the more common type of succession, occurs on a surface
where an ecosystem has previously existed
Secondary succession occurs in ecosystems that have been
disturbed or disrupted by humans, animals, or by natural
processes such as storms, floods, earthquakes, and volcanoes.

18. PIONEER SPECIES
 The first organisms to colonize any newly available area and begin
the process of ecological succession.
 Over time, pioneer species will make the new area habitable for
other species.
Climax Community
 It is a final stage and stable community.
 Even though a climax community continues to change in small
ways, this type of community may remain the same through time if
it is not disturbed.

19.  Lichens (left) are colonizing a boulder. Over a long period of time, lichens can break down rock into
soil.
 Plants that grow through cracks in city sidewalks (right) can also be described as pioneers of primary
succession.

20.  When Mount St. Helens erupted
in 1980, much of the forest
around the volcano was
destroyed.
 The photo above was taken 12
years after the eruption of Mount
St. Helens and shows evidence of
secondary succession.

21.  This fire fighter is helping
maintain a controlled fire in South
Dakota.
 Some fires are set on purpose by
fire officials to bring nutrients to
soil from burned vegetation.
 These young lodge pole pine
trees have started growing after a
devastating forest fire.

22. OLD-FIELD SUCCESSION
Another example
of secondary
succession is old-
field succession,
which occurs when
farmland is
abandoned.