49 Community Ecology Lab
Lab adapted by Staci Forgey and Dr. James Holden, Tidewater Community College biology faculty, with permission from Dr. William Edwards, biology faculty at Niagara University.
Lab Objectives
- Describe the processes of primary succession and secondary succession
- Explain what makes a community and an ecosystem different
- Describe the differences between abiotic and biotic factors
- Explain why disturbances play an important role in the progression of succession
- Define a climax community
- Describe why most areas will not make it to a climax community
- Describe the plant communities present after glacial succession and how they change the environment
- Explain the stages of succession of milk
- Describe how pH changes as milk goes through successional stages
- Explain the difference between Gram-negative and positive bacteria
- Draw and describe the shapes of bacteria
- Formulate a hypothesis based on background data
Download a PDF of the lab to print.
Ecological Succession of Bacteria in Milk
The communities within ecosystems develop over time, from very simple species assemblages, to complex, rich ecosystems. In this process, called succession, each succeeding species facilitates changes in the environment which allow new species to come into the ecosystem. As the community becomes more and more complex, the biodiversity of the ecosystem also increases. Both biotic and abiotic processes can reset the succession process. That is, events caused by both the community itself and outside events can return the community to an earlier succession state. The gradual changes in the community are both orderly and predictable in many ecosystems. The peak or most complex, advanced community that can develop in any abiotic environment is called the climax community. The picture below describes the developing communities as a series of steps, each of which can be driven against the succession process by disturbances:
Question
- What types of events could “reset” a succession process? Name at least one biotic and one abiotic disturbance.
One example of a severe disturbance, reducing the land to bare ground, is the passage of a glacier. Though glaciers have not covered this part of North America for ten thousand years, there are parts of the continent that are even now being uncovered by receding glaciers. One area is the Pacific Northwest. From Juneau to Glacier Bay, many glaciers that have previously fallen directly into the ocean are now leaving bare soil that has not been exposed for more than fifty thousand years. Because the glaciers retreat very slowly, we can watch communities change over time in a single snapshot. Take the glaciers of Glacier Bay National Park, midway between Juneau and Anchorage, Alaska. The glaciers there have been retreating since the explorer Vancouver’s first expedition in 1794. Since then, the retreat has covered over 100 km, including new coastlines, meadows, and mountains:
Question
- Explain how thi