Biodiversity, Species Interactions, and Population Control
1. Two major factors affect the number of species in a community: the latitude in terrestrial communities and salinity/nutrients in aquatic systems.
2. Species play different roles in a community. Native species sustain the ecosystem in which they are a part. Some nonnative species will crowd out native species. Indicator species alert us to harmful changes in the community. Keystone species play ecological roles in the specific community: they may assist in pollination help regulate populations. Foundation species affect the community’s habitat to benefit other species.
3. Species interact with each other in these different ways: interspecific competition, predation, parasitism, mutualism, and commensalism.
4. As environmental conditions change, one species may be replaced by other groups of species. This gradual change in the composition of species in a given area is called ecological succession.
5. A community has three aspects of sustaining itself: its persistence, the ability to resist being altered, its constant population, and its resilience in repairing damage. High biodiversity may give a community some edge in surviving, but we do not know this for certain.
Key Questions and Concepts
5-1 How do species interact?
CORE CASE STUDY. Sea otters are a keystone species found on the west coast of the United States that are endangered. For many years they have been in recovery. Why should we be concerned about their status? Sea otters are charismatic, they generate tourist revenue, and they are very valuable in terms of controlling biological populations.
A. Five basic species interactions are competition, predation, parasitism, mutualism, and commensalism. B. Competition between species for food, sunlight, water, soil, space, nest sites, etc. is interspecific competition. 1. With intense competition for limited resources,