Download Final Examination What is a Community?

Final Examination
35 - 40 Questions:
~5 – Exam I
~35 – Populations,
Communities, and
Ecosystems
http://www.vcld.org/pages/newsletters/01_02_fall/testtaking.htm
What is a Community?
• An ecological community consists of all
the interacting populations in an
ecosystem.
• Interactions among populations in a
community limits their abundance,
distribution, and density.
– Populations are associated with resource
availability.
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Habitat Change
Ecological Succession
Ecological Succession: a change in species composition
through time in response to an environmental change, which
they change structurally over time.
Habitat Change
Ecological Succession
• Succession is usually preceded by a disturbance
– A physical event that disrupts the
community/ecosystem either by altering the
community, its abiotic structure, or both.
Habitat Change
Plant Succession
Succession after disturbance in a given area often
involves a relatively repeatable sequence of species
replacements over time.
Succession is usually studied in plant
communities and those of sessile animals, but all
communities may undergo this process.
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Habitat Change
Plant Succession
The types of species in an area (referred
to as species composition) is influenced by:
- Climate
- Soil Conditions
- Topographic Features
- Disturbances
Biotic and Abiotic
(living) and (non-living)
Time
Habitat Change
Plant Succession
• During succession, most terrestrial communities go
through stages
– Succession often progresses to a relatively stable and
diverse climax community.
– Recurring disturbances can set back the progress of
succession
• Maintain communities in
subclimax stages.
Primary
Succession
• During succession, most terrestrial communities
go through stages
– Succession begins with arrival of a few hardy
invaders called pioneers.
• They alter the ecosystem
in ways that favor other
species, which
eventually displace the
pioneers.
3
Secondary
Succession
• Secondary succession occurs after a
disturbance changes, but does not obliterate an
existing community
– Often takes just
hundreds of years.
– Example:
succession when
a disturbance
leaves behind soil
and seeds.
Climax Communities
• Unless disturbances intervene, succession
usually ends with a relatively stable climax
community
• Species in climax communities have narrower
niches than pioneer species
– Allows many species to coexist without replacing
one another
Climax Communities
• Climax species tend to be larger and longerlived than pioneer species
• The exact nature of the climax community at a
site reflects local geological and climatic
conditions
– Examples: type of bedrock, temperature, and
rainfall
4
The Edge Effect
Ecotone
Edge
Edge/Ecotone: A
narrow band of overlap
between/among
communities that denote
changes in the physical
state of the habitat.
Ecotone
Community Ecology
Key Concepts
1. A habitat is the type of place where individuals
of a species normally live. A community is an
association of all the population of species that
occupy the same habitat.
Community Ecology
Key Concepts
2. Every species in the community has its own
niche, defined as the sum of all activities and
relationships in which its individuals engage as
they secure and use the resources required for
their survival and reproduction.
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Community Ecology
Key Concepts
3. Community structure begins with
adaptive traits that offer individuals
of each species the capacity to respond to the
physical and chemical features of their habitat,
and to the levels and patterns of resource
availability over time.
Community Ecology
Key Concepts
4. Interactions among species influence the
structure of the community. They include
mutually beneficial reactions & interactions,
competition, predation, and parasitism.
© Thomas D. Mangelsen (USA)
Community Ecology
Key Concepts
5. Community structure depends on the geographic
location and size of the habitat, the rates at
which the member species arrive and disappear,
and the history of physical disturbances to the
habitat.
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