Download Niche and Biodiversity

Community interactions are classified
by whether they help, harm, or have
no effect on the species involved
• Ecologists call relationships between species in a
community interspecific interactions
• Example: Interspecific competition
• Interspecific interactions can affect the survival and
reproduction of each species, and the effects can be
summarized as positive (+), negative (–), or no effect
(0)
Competition
• Interspecific competition (–/– interaction) occurs
when species compete for a resource in short supply
Competitive Exclusion
• Strong competition can lead to competitive exclusion,
local elimination of a competing species
• The competitive exclusion principle states that two
species competing for the same limiting resources
cannot coexist in the same place
Ecological Niche
• A plant's or animal's ecological niche is a way
of life that is unique to that species.
• Niche and habitat are not the same. While
many species may share a habitat, this is not
true of a niche. Each plant and animal species
is a member of a community.
• The niche describes the species' role or
function within this community.
• For example, the red fox's habitat, which might include
forest edges, meadows and the bank of a river, is
shared with many animals .
• The niche of the red fox is that of a predator which
feeds on the small mammals, amphibians, insects, and
fruit found in this habitat. Red foxes are active at night.
They provide blood for blackflies and mosquitoes, and
are host to numerous diseases. The scraps, or carrion,
left behind after a fox's meal provide food for many
small scavengers and decomposers. This, then, is the
ecological niche of the red fox.
• Only the red fox occupies this niche in the meadowforest edge communities. In other plant communities
different species of animal may occupy a similar niche
to that of the red fox.
• Changing one factor in an ecosystem can
affect many other factors.
• A keystone species is a species that has an
unusually large effect on its ecosystem.
Keystone
If you moved this stone the
whole arch would fall down
Reintroducing Wolves to Yellowstone
National Park
http://vimeo.com/86466357
Beaver
http://vimeo.com/28055044
Keystone species form and maintain
a complex web of life.
creation of
wetland
ecosystem
increased waterfowl
Population
keystone species
increased
fish
population
nesting
sites for
birds
Diversity and trophic structure characterize
biological communities
• In general, a few species in a community exert
strong control on that community’s structure
• Two fundamental features of community structure
are species diversity and feeding relationships
Species Diversity
• Species diversity of a community is the variety of
organisms that make up the community
• It has two components: species richness and
relative abundance
– Species richness is the number of different
species in the community
– Relative abundance is the proportion each
species represents of all individuals in the
community
Figure 54.10
A
B C
D
Community 1
A: 25% B: 25% C: 25% D: 25%
Community 2
A: 80% B: 5% C: 5% D: 10%
• Communities with higher diversity are
– More productive and more stable in their
productivity
– Better able to withstand and recover from
environmental stresses
– More resistant to invasive species, organisms
that become established outside their native
range