This document discusses community ecology and the interactions between species within a community. It defines a community as all the populations inhabiting the same area and interacting with each other and the environment. Relationships between species can include symbiotic relationships like mutualism, commensalism, parasitism, and others. Ecological succession is also discussed, including primary and secondary succession, pioneer species, and climax communities.

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.