Bi 101 (Summer 2006)
Ecology: Community Interactions
Dr. Dutton
Why Are Community Interactions Important?
The interactions among populations within a community serve to maintain a balance between
available resources and the number of …
As the interactions among the populations serve to limit population size, they also lead to …
changes in characteristics and behaviors, increasing the
_________________________ of the total population. This is …
_________________________
When changes in one species results in adaptive changes in an interacting species ...
_________________________ has occurred
What Are the Effects of Competition Among Species?
_________________________ among species, or _________________________
_________________________, has such a strong effect on the species involved that each
evolves ways to reduce any overlap in needs
In other words, each species specializes within the community, developing its
own well-defined, ________________________ ________________________
Adaptations Reduce the Overlap of Ecological Niches Among Coexisting Species
The _______________________ _______________________ _______________________
- no two species can inhabit exactly the same ecological niche simultaneously and
continuously
- just as no two organisms can occupy exactly the same physical space
When two or more species with similar requirements coexist, they typically occupy a smaller
niche than either would if by themselves. This is …
_________________________ _________________________
Figure 40-2
If one of the competing species is removed from the community, the other species may expand
its niche since the competition pressure has been reduced
What Are the Results of Interactions Between Predators and Their Prey?
_________________________ interactions have intense effects on the species involved
Predators have evolved ways to best capture their prey, while the prey have evolved
mechanisms to elude their predators
This _________________________ has resulted in some very complex physical characteristics
and behaviors
Know the examples from your text!
Bats and their moth prey have developed complex "cat and mouse" behaviors, while other
species _________________________ themselves to avoid predators or detection by prey
(Figure 40-4)
In contrast to camouflaged species, others stand out with bright or
_________________________ _________________________ (Figure 40-7)
These species advertise their presence ...
Their _________________________ _________________________ are bright colors that warn
potential predators that they are poisonous or otherwise distasteful and are to be avoided
Species with common characteristics may share warning patterns as well; for example, stinging
insects tend to be bright yellow with black stripes, and poisonous frogs from the tropics
display very colorful skin pigments
Some harmless species have evolved to _________________________ their poisonous
relatives
Mountain King Snakes (non-venomous), for example, have colorful stripes similar to Coral
Snakes (venomous) (Figure 40-8)
“Devious” predators exists as well:
_________________________ _________________________ has evolved among species
that resemble harmless species
Predators, however, may be caught off-guard
Some prey make use of color patterns that mimic a larger organism
These species use their _________________________ _________________________ to
scare away predators (Figure 40-10)
Some prey species have the ultimate defense: "_________________________
_________________________ "
Coevolution, however, has also lead to a few predator species that are not harmed by the
chemical produced and may even use it as its own defense mechanism
What Is Symbiosis?
Within a community, interacting with other species is unavoidable; however, some species have
such close interactions that they have developed _________________________ relationships
When one species of the relationship benefits and the other is unaffected, the relationship is ...
_________________________
If one species benefits and the other is harmed, the relationship is ...
_________________________
If both species benefit, the relationship is _________________________
Let’s Summarize the possible interactions among organisms (Table 40-1)
How Do Keystone Species Influence Community Structure?
The influence of species on community structure is not necessarily equal
When one species has a role that is out of proportion to its population size, that species is a
_________________________ in the community
Often, a keystone species cannot be identified until it has actually been …
At this point it may be too late to reduce the impact its absence will have on the community
Succession: How Do Community Interactions Cause Change over Time?
The interactions among members of a community lead to structural changes within that
community; changes that are identified as stages in _________________________ of the
community
_________________________ succession begins with _________________________
species such as lichen and mosses establishing a hold on bare rock
Figure 40-15
As soil slowly forms, additional species move into the young community in a recognizable
pattern
_________________________ succession occurs after an established community has been
disturbed perhaps by fire, wind storm, or farming
If left undisturbed, succession will continue to a stable endpoint, the
_________________________, determined in a large part by ...
the geography and climate of the area
Figure 40-16
If a community is regularly disturbed, it will be maintained at a succession point below the
climax, a _________________________
Climax communities covering broad geographical regions are _________________________
Biomes are distinguished by specific climatic conditions and characterized by specific plant
communities
Summary: Major Points
This chapter has covered:
1. How organisms interact with members of their own species, as well as with members of
different species
2. That these interactions include mechanisms that have evolved to deal with competition for
limited resources, predator/prey relationships, and symbiotic relationships
3. That the species that are present in a community depends on the ecosystem that is present
4. How an ecosystem changes over time (succession)