Points to Consider
- Now that you understand what makes up a population, what do you think makes up
a community? - You have learned about some of the factors that limit populations. What do you think
are some interactions that affect the community?
23.3 Lesson 23.3: Communities
Lesson Objectives
- Explain what a community is.
- Describe community interactions
- Explain what competition is and how it affects the community.
- Describe predation and how that affects prey density.
- Explain what symbiosis is and give examples of different kinds of symbiosis.
Check Your Understanding
- What is a population?
- How do density-dependent factors promote competition between members of the same
population?
Introduction
Now that we have examined the dynamics of a single species at the population level, we are
now ready to move to the next higher level. This is the community level, where we look at
how populations of different species that occupy the same area interact with each other. As
we will see, there are a number of types of interactions, including competition, predation
and symbiosis. These interactions in turn affect the species’ interactions with one another.
What is a Community?
Acommunityis an assemblage within the same area, of populations of different species
interacting with one another. The term can be used in various ways with differences in
meaning. For example, it may be limited to specific places, at specific times, or certain types
of organisms. Thus, one may study the fish community in Lake Ontario or the fish in this
lake during a specific period, such as the period before industrialization.