Transcript Community Interactions and Disturbances PPT

Community Interactions and
Disturbances
Chapter 35
Sections 4 and 5
Chapter 36
Section 5
What is a Community?
A community is formed when populations of
different species live together in a certain area.
Sharing close living quarters forces them to
interact.
Competition Between Species
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Interspecific Competition
occurs when two or more
species rely on the same
resource, such as food,
water, or space.
Competitive Exclusion
occurs when competition
leads to a clear winner and
clear loser.
Within a community, each
species has a unique niche
(or living arrangement)
No two species can have the
exact same niche!
Kenai Fjords National Park
Predation
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The interaction in which
one organism eats another
Both predators and prey
evolve adaptations to
survive (camouflage,
stingers, poisonous
chemicals, etc.)
Symbiotic Relationships
A close interaction between species that live in or on
each other:
 Parasitism- One organism (parasite) obtains its
nourishment at the expense of the other (host)
Ex: tapeworm in intestine
 Mutualism- Both species benefit
Ex: bees and flowers
 Commensalism- One organism benefits and the other
is neither helped nor harmed
Ex: Barnacle on a whale
Disturbance in a Community
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Communities tend to be in a continual state of
change
Natural disturbances such as fires, volcanic
eruptions, floods, and tornadoes can destroy
organisms and their resources
Fortunately, some organisms thrive in the
wake of destruction. The process of rebuilding
the community is called ecological succession
Types of Succession
PRIMARY
When a community
arises out of a lifeless
area that has no soil
Lichens and moss are pioneer species
SECONDARY
When a disturbance
damages an existing
community but leaves
the soil intact
Climax Community
A stable group of plants and animals that is
the end result of the succession process
Does not always mean big trees:
Grasses in prairies
Cacti in deserts
Human Disturbances Threaten
Communities and Biodiversity
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Humans clear-cut forests for lumber and land
We also intentionally or accidentally introduce
exotic species to communities when we travel from
one geographic region to another. The invasive
species may out compete or prey upon native
species.
Overexploitation reduces population size and can
threaten species to the point of extinction
Conservation can slow the loss of
Biodiversity
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Biodiversity is import to the health
and sustainability of ecosystems
because species are interconnected
We can practice conservation by
protecting “hot spots”, understanding
species habitat, and balancing
demands for resources.
Sustainable development is about
developing resources so that they can
renew themselves and be available
for the future.