Science Lesson on Eco-systems

Students Create and Observe Plant and Animal Community in a Jar

Feb 28, 2009

Elementary and middle school students collect water samples, observe the life within, and learn to record their scientific observations in science journals.

In the forward to Gaia's Garden by Toby Hemenway [Chelsea Green Publishing, 2003], John Todd describes a powerful teaching tool for observing the complex interactions of the natural world. This simple activity allows students to observe intricate relationships between small organisms over time, while developing their observation and recording skills.

Students need to collect three water samples (not tap water) from three different sources. Water can come from a roadside pool, a marshy area, a lake, a creek, an animal wallow, or garden pond. Any water that has not been treated will provide a suitable sample.

Students mix their three water samples together in a quart jar, leaving an inch or two of head space, screw on the lid, and invert the jar. The jars are then placed in a sunny spot on a window ledge. In their science journals students record the date, the source of their three water samples, anything they've noticed, and any predictions they have. Since most jars just look like muddy water, student expectations fairly low.

At first all the jars of water are likely to be turbid, but over the next few days life in the jars will begin to organize itself. Take a few moments each day to have students observe what they see, and record it in their science journals. Magnifying glasses help students focus on the small plants and animals in their jars.

Teach Students How to Record Science Observations

Agree upon what basic information students will record each time they observe their jars. As a minimum, students should record the date, the weather (sunny or overcast), and the room temperature, since these variables may make a difference to the activity in the jars. Encourage students to use detailed diagrams as well as text to record their observations. Record approximate numbers of various organisms, activity level in the jar, any changes since the last viewing.

Life Organizes in the Jar

Initially the sediment in the water will settle to the bottom, microscopic plants will float to the top, and bubbles of oxygen will appear under the plants. Bottom dwellers will take up residence in the sediment that has settled out, aquatic weeds will begin to grow, and small swimming animals will appear.

Students will be able to observe life cycles, predator-prey relationships, food chains and more. Each jar will be different, since each student has collected his or her water from different sources, yet, as John Todd notes, despite the differences, all of the jar communities share the ability to organize and sustain themselves. They all produce oxygen, recycle wastes, and perpetuate life.

To demonstrate the role sunlight plays in sustaining life, put some control jars in a place where they will not receive sunlight. These jars are quickly overcome with waste products from the organisms within. They become murky dead zones. If the life within is not completely dead, moving these jars to sunlight will renew them, and they too will organize and sustain themselves.

Watching life in the jars can be a yearlong activity. John Todd has had a jar of water on his desk for years. Many students choose to keep their jars at the end of the year, and report back many years later that life continues to thrive in the micro-world of their quart jar.

The copyright of the article Science Lesson on Eco-systems in Curricula/Lesson Plans is owned by Sheila Gaquin. Permission to republish Science Lesson on Eco-systems in print or online must be granted by the author in writing.