Brine+Shrimp

by John A. Cigliano, Ph.D., Cedar Crest College
 * Tolerance for varying environmental conditions in Brine Shrimp**

__**Learning Goals for DVI Fellows:**__

Organisms evolve adaptations that maximize their fitness (survival and reproduction) given the environmental conditions (biome) that they live in. Example: Animals living in cold regions must have thick fur to keep warm where animals living in hot, dry regions must be able to dissipate heat and retain moisture.

Because of this, organisms can only survive and reproduce over a range of environmental conditions. This range will vary for specific conditions and among species. For example, reef building corals can only survive in water that where the average temperature between 18°C and 40°C, with an optimum range of 23-25C and a salinity range of 32-35 psu. This is known as //tolerance//: the ability of an organism to function (i.e., grow, survive and reproduce) within a minimum and maximum range of conditions. //Conditions// are abiotic (physiochemical) features of the environment that are not consumed by organisms and do not become limited (e.g., salinity, pH, temperature, humidity).

The **learning goals** of this workshop include:
 * developing an understanding of the concept of tolerance and how it relates to natural selection and adaptation
 * learning how to develop and test (appropriate) hypotheses.

The **learning objectives** include:
 * develop an appropriate hypothesis and prediction to answer the research question: “What is the tolerance range for [environmental condition] in brine shrimp.”
 * plan and execute an experiment to test the prediction
 * analyze, graph, communicate and discuss results with the entire group.

__**Summary of Activities:**__

Why do organisms live under a specific, and sometimes, narrow range of environmental conditions? Think polar bears in the arctic. Think cactus in the desert. Less common examples include the salt marsh grass //Spartina alterniflora//, which can live in soil that is nearly anoxic while its congener //S. patens// cannot grow in anoxic soil. Then there is the barnacle //Chthamalus stellatus//, a southern species of barnacle found in the British Isles. This barnacle is restricted by temperature to the western British coast because it cannot survive in the colder waters off the eastern coast; its upper limit in the intertidal zone is restricted primarily by its ability to resist desiccation and also its tolerance for high temperatures. This species is more tolerant to desiccation and heat than is the barnacle //Semibalanus balanoides//. This species does not make it as high up in the intertidal zone as //C. stellatus//.

The answer is that organisms have evolved to grow, survive, and reproduce within a range of environmental conditions. For some organisms, the range is narrow but in other organisms the range is more broad. This is known as //tolerance//: the ability of an organism to function (i.e., grow, survive and reproduce) within a minimum and maximum range of conditions. //Conditions// are abiotic (physiochemical) features of the environment that are not consumed by organisms and do not become limited (e.g., salinity, pH, temperature, humidity). When organisms find themselves in conditions that are optimal, they do well (i.e,, grow, survive, and reproduce). When conditions are marginal, they don’t do so well: they might survive, barely, but not reproduce. When they find themselves in conditions that are outside their tolerable range (too hot, too cold, too acidic, not enough moisture. etc.), they either move or die. The effect that an organism’s response to environmental conditions has on it’s survival, growth, and reproduction is known as the //Shelford's Law of Tolerance//.

This activity is a study of tolerance for varying environmental conditions in brine shrimp. Brine shrimp is being used as a model organism; this concept is applicable to all organisms. This activity can be used to study the tolerance of other animals and plants; any organism that can be easily grown in the classroom (e.g., //Daphnia//, Fast Plants) can be used. Working in groups, you will develop a hypothesis, prediction, and experiment to answer the question: “What is the tolerance range for [environmental condition] in brine shrimp.” Each group will also develop a tolerance curve. A tolerance curve is a graphical representation of an organism’s tolerance to certain environmental conditions. Each group will communicate its results to the entire group and we will discuss the hypothesis and experiment and what the results mean. We will also discuss how to apply this to other organisms in the classroom.

Background information on the ecology and natural history, as well as how to raise brine shrimp can be found at:

http://animaldiversity.ummz.umich.edu/site/accounts/information/Artemia_salina.html

http://web.archive.org/web/20070814003850/http://web.cecs.pdx.edu/~davidr/discus/articles/artemia.html

http://ut.water.usgs.gov/shrimp/index.html

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