Ecosystem in a Jar

Chapter

In September 1993, the first mission of Biosphere II, the largest self-sustaining

closed ecological system ever made, came to a close. From its 3600 kiloliter, coral-filled ocean to its emerald rain forest, this unique laboratory was designed to study the fundamental ecological processes on Earth. Biosphere II demonstrated that there must be a dynamic balance between biotic and abiotic factors in the environment, and that two conditions must be met if an ecosystem is to remain stable: energy from sunlight must be converted into energy usable by organisms, and organic and inorganic nutrients must be recycled back into the environment. In this activity, you’ll test this idea by constructing a sealed, mini- environment of your own.

Procedure:

1. Obtain a small, clean glass jar with lid. A small jelly orpickle jar works best. Mark your name on the lid.2. Spread a 4–5 cm layer of sand on the bottom of the jar.3. Slowly fill the jar three-fourths full with distilled wateror tap water that has aged at least three days. Allow sandto settle on the bottom of the jar.4. Carefully plant a live Elodea or other freshwater plant inthe sand. Gently trim the top of the plant to fit the sizeof the jar, and make sure it is completely submerged.. Use a dropper to pick up several (7–10) Daphnia, andadd these to the jar. Add a pinch of brewer’s yeast to thejar to serve as a temporary food source for the Daphnia.6. Close the jar and place your mini-environment in asunny area or near some other light source. You’ve justconstructed a self-sustaining, balanced ecosystem thatcan last from several months to a year.

1. With the addition of live plants, nutrient-recycling bacteria were also introduced to your minienvironment.

Bacteria, as well as yeast, serve as food for Daphnia. In your own words, describe whyyour mini-environment is a balanced ecosystem. Include the words consumer, producer, and decomposerin your answer.2. A food chain is the specific sequence in which organisms obtain energy in an ecosystem. In the space below, diagram the food chain in your mini-environment. ________________________________________________________________________________________________________________________________________________________

3. Ecosystems will remain in equilibrium unless disturbed by external factors. Describe the ecological consequences of the following situations. ________________________________________________________________________________________________________________________________________________________a. A rare disease kills all the Daphnia in the mini-environment.________________________________________________________________________________________________________________________________________________________b. The mini-environment was placed in a dark part of the room.________________________________________________________________________________________________________________________________________________________c. Elodea plants were thoroughly cleansed of all bacteria before being planted.________________________________________________________________________________________________________________________________________________________4. Describe how carbon and oxygen are recycled in your mini-environment._______________________________________________________________________________________________________________________________________________________

Source: Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc