Designing a Biological Community

This page authored by Charles Dodd, Shoreline Community College.
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This page first made public: Oct 9, 2012


In this Physical Geography Lab, students are responsible for designing a simple biological community. Students are provided abiotic environmental conditions specific to certain geographic areas. Students then design a community of decomposers, producers and consumers. Students are required to select appropriate species from a list provided to them consistent within the constraints of food avalibility within their community and the abiotic conditions of their environment. Students are required to identify and describe trophic structure, different interspecific relationships, biomass patterns as well as keystone species if relevant. This assignment places emphasis on the aboitic components of climate and its role in influencing biological communities.

Learning Goals

Students should learn the trophic structure and relationships of a community, limiting factors to species, the role of diversity in community stability and complexity. Differences in abiotic conditions influencing community structure, diversity and size (biomass) are the meta-theme of this exercise. Basic quantitative skills involving addition, subtraction, multiplication and division, and the use of ratios are also emphasized.

Context for Use

This is a Lab Exercise and is intended for 1st and 2nd year college introductory Physical Geography courses. This exercise is designed as a group exercise (3-4 students per group). Ideally there are five to six groups within the class.

Description and Teaching Materials

Students receive instructions for the exercise including background description, specific objectives of the assignment, a table of species and their characteristics, and abiotic conditions associated with each environment. Each group is assigned an "environment" with abiotic environmental conditions in terms of minimum light (shortest period of light during the year), minimum and maximum temperatures during the course of the year, minimum and maximum annual precipitation, and total nitrogen availability for a given area. It is important to note that this exercise represents a model. ALL VALUES IN THIS EXERCISE ARE ABSTRACT AND DO NOT REFLECT REAL MEASUREMENTS.

Student groups are then asked to do the following:

a) the species that can exist in their community

b) number of individuals (population) of each species in their community

c) calculate the total biomass for each species, and calculate the total biomass for each trophic level

d) draw a simple representation of their community's food web

e) identify and discuss the significance of any "keystone" species in their community

f) describe the role of decomposers and detritivores in their community

g) present their findings in a powerpoint format identifing and describing: 1) the biome the their environement community best conforms to, 2) the trophic structure of their community, 3) the existance and role of any keystone species

This assignment includes the following items

Designing a Simple Biological Community

5 Different Environments

A Biological Community Matrix

An Example of Calculating Producers Biomass using the Community Matrix

An Example of Calculation Primary Consumer Biomass using the Community Matrix

Designing a Simple Biological Community (Microsoft Word 133kB Aug23 11)

Environment A (Microsoft Word 34kB Aug22 11)

Environment B (Microsoft Word 34kB Aug23 11)

Environment C (Microsoft Word 34kB Aug23 11)

Environment D (Microsoft Word 34kB Aug23 11)

Environment E (Microsoft Word 34kB Aug23 11)

Community Matrix Example (Microsoft Word 67kB Aug23 11)

Community Matrix Example Step 1 Producers (Microsoft Word 50kB Aug23 11)

Community Matrix Example Step 1 Primary Consumers (Microsoft Word 70kB Aug23 11)

Teaching Notes and Tips

The most common problems with this assignment are: 1) determining which species are adapted to the abiotic conditions of the environment the group is given 2) calculating decomposers

References and Resources

Hess, Darrel. McKnight's Physical Geography: A Landscape Appreciation, 10th ed. (Pearson Prentice Hall, 2011) Chapter 10 "Cycles and Patterns in the Biosphere" pp. 261-271; Chapter 11 "Terrestrial Flora and Fauna" pp. 302-313

Luoma, Jon. The Hidden Forest: The Biography of an Ecosystem, (Oregon State University Press, 2006), pp. 68-89; 92-101.

Evergreen State College