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Essential Science for Teachers: Life Science

Bottle Biology | Bottle Basics The EcoColumn

The EcoColumn

As one of the most encompassing levels of organization in the living world, an ecosystem is defined as a community of organisms along with their physical environment. The EcoColumn (see building instructions) is designed to model an ecosystem on a small scale. Its components include a terrestrial habitat with a compost unit and an aquatic habitat. We built ours by establishing a TerrAqua Column first and then adding to it—you can build yours the same way or as a complete system from the start.

The Life Science EcoColumn is designed as a study system for concepts addressed in the videos for Session 7 (Energy Flow in Communities) and Session 8 (Material Cycles in Ecosystems). This system provides opportunities to understand how energy is brought into the living world and transferred through food chains, and how the living and nonliving environments are intimately connected through cycles of matter.

Life Science has suggested several activities for the EcoColumn. “Taking Inventory” and “Pondering Change” (also suggested for the TerrAqua Column) provide baseline data for studying the system over time. “What’s on the Menu” examines the energy sources of the organisms in the EcoColumn, which makes it possible to construct a food web. “Basically, I’m a Fungi” reveals a portion of the food web that usually remains unseen in natural settings: the yeasts and molds that act as decomposers. “When It Rains…” turns the EcoColumn into a model of the water cycle. And “Decomposition Tea” compares the growth of plants in distilled water and fertilizer solution versus water that has flowed through the terrestrial and compost components of the EcoColumn.

You can follow along online and “Track Our Progress” with the “Basically, I’m a Fungi,” and “Decomposition Tea” activities.

For more background information and additional activity ideas, you can visit the Bottle Biology Web site at

Build the System: Building Your EcoColumn

The EcoColumn starts with the basic units for a TerrAqua Column — an aquatic and terrestrial habitat — and adds an additional unit in between to act as a compost habitat.

What you stock your EcoColumn with involves your goals for study, the sources of your specimens — local or purchased — and your own creativity. To apply concepts from the videos, it will help you to think about including producers, consumers, and decomposers. The simplest way to stock your EcoColumn is to collect from your local environment so that you can model the ecosystem in which you live. To provide a breadth of examples, we combined local collections with purchased specimens to make our system particularly diverse.

Activity Accessories

Depending on the activities you choose to do, you may need one or more of the following:

  • Petri plates with prepared media (for “Basically, I’m a Fungi” activity
  • 3 Bottle Growing Systems (for “Decomposition Tea” activity)


Materials Needed

For Building

  • Three two-liter plastic bottles (bottle 1 provides a deep base and top, bottles 2 and 3 provide deep funnel units)
  • Three bottle caps (for top and deep funnel units)
  • One 20-cm length of nylon craft cord (for wick)
  • China or non-permanent marker (for making marks)
  • Safety razor or utility knife (for starting bottle cuts)
  • Scissors (for finishing bottle cuts)
  • Soldering iron or drill (for making wick hole in bottle cap)
  • Push pin (for making air holes)

Note: For more information on column construction, visit Bottle Basics.

For Stocking and Maintaining

It’s very important that all materials introduced into the EcoColumn — living, dead, or nonliving — are clean and free of anything that might be toxic to living things (e.g., oil, pesticides, etc.). The organisms you introduce should be small and suited to the habitats you construct. The number of organisms you introduce will depend on what they are, but it is better to add too few than too many, especially in the aquatic habitat. Bigger organisms should definitely be limited to one or two.

You can download an inventory of aquatic and terrestrial plants and animals (PDF) that Paul Williams has found make good choices. Many varieties can be collected from local environments and most can be purchased from Carolina Biological Supply Company (1-800–334–5551) or The Bottle Biology Web site is also a resource for materials “custom designed” for bottle systems like this.

Aquatic habitat

  • Fine grained aquarium gravel (provides “bedrock”)
  • Sand or topsoil (provides bottom sediment)
  • Untreated tap water or distilled water (provides aquatic habitat)
  • “Boulders,” “sunken logs,” and other miniature objects typical of a pond bottom
  • Aquatic plants and animals
  • Fish food (if you include a fish)

Compost habitat

  • Fine grained aquarium gravel (provides “bedrock”)
  • Sand/topsoil mix (provides soil substrate)
  • Leaf litter (provides compost habitat)
  • A few chunks of turnips, potato, apple, or other roots, stems, or fruits
  • Twigs
  • Earthworms, pill bugs, millipedes, and other natural inhabitants of leaf litter

Terrestrial habitat

  • Fine-grained aquarium gravel (provides “bedrock”)
  • Topsoil (provides soil substrate)
  • Leaf litter (provides decaying material)
  • “Boulders,” “dead trees,” and other miniature objects typical of a forest habitat
  • Terrestrial plants and animals
  • Food for animals as needed

Building Instructions

  1. Follow the instructions in Bottle Basics for making a deep base unit, two deep funnel units, and a top unit. An internal unit for either the aquarium or terrarium is optional.
  2. Melt or drill a hole in two of the bottle caps and screw onto the deep funnel units.
  3. Insert the wick through the hole in the bottle cap of what will be the lower deep funnel (compost habitat) with approximately 10 cm on either side.
  4. Invert the upper deep funnel (terrestrial habitat) over the lower and invert both over the deep base (aquatic habitat). Then, secure the top.
  5. Add air holes to the upper areas of each habitat.
  6. If you wish to string your system, refer to the instructions for stringing bottles in Bottle Basics.

Stocking Instructions

Aquatic habitat

  1. Add a layer of sand or topsoil (2-3 cm) to the deep base.
  2. Add a layer of gravel (1-2 cm) on top of the sand or topsoil.
  3. Add water to a level about 1cm below the cap of the lower deep funnel.
  4. Plant aquatic plants with roots in the bottom sediment. A chopstick will help you push the stems or roots into the ground.
  5. Arrange “boulders” and other objects on the bottom sediment.
  6. Add floating aquatic plants.
  7. Let the aquarium sit until the sediment settles.
  8. Add aquatic animals.

Compost habitat

  1. Add a 1 – 2 cm layer of gravel to the deep funnel.
  2. Mix equal parts of sand and topsoil together and add a layer (2 – 3 cm) over the gravel.
  3. Add leaf litter and twigs to about 1 cm below the cap of the upper deep funnel.
  4. Mix food items in, moving them to the sides of the habitat for better observation.
  5. Add compost animals as needed (you will probably collect some with the leaf litter).
  6. Establish a “water connection” between aquatic and compost habitats by slowly pouring water down the side of the terrarium until it drips from the bottle cap into the aquarium. This is essential to ensure “wicking” action.

Terrestrial habitat

  1. Add a layer (1-2 cm) of gravel to the deep funnel.
  2. Mix equal parts of leaf litter and topsoil together, moisten, and add a layer (6-8cm) over the gravel.
  3. Add terrestrial animals that burrow to the soil (e.g., worms).
  4. Plant terrestrial plants in the soil.
  5. Arrange “dead trees” and other objects on soil.
  6. Add the remaining terrestrial animals.

Maintenance Instructions

  1. Provide a light source, preferably indirect window light. A small desk lamp or plant light will work, too. For artificial lights, provide 12 – 14 hours of light daily.
  2. Add a small amount of water to the terrestrial habitat weekly or when it appears to be drying out. A fine spray of water on the plants also maintains the unit well.
  3. Remove algae in the aquatic habitat weekly. Gather filamentous algae by “spooling” with a toothbrush or tweezers. Remove algae along the sides of the bottle with a paper towel.
  4. Change the water in the aquatic habitat weekly. Use a turkey baster to remove and replace 25% of the water each week.
  5. Regularly feed animals that require an external food source.

Petri plates with prepared media

Materials Needed

  • One package of 10 petri plates prepared with Sabouraud Dextrose Agar
  • One package of 100 sterile swab applicators

Both of the above can be purchased from Carolina Biological Supply Company (1-800–334–5551) or Store unused media upside-down in a refrigerator.

Bottle Growing System

The instructions for the Bottle Growing System are provided as part of the Brassica & Butterfly System. There are two suggested modifications for the “Decomposition Tea” activity. The first is to use substrate (i.e., soil) that is free of nutrients. While this isn’t absolutely necessary, if the substrate already contains nutrients, it will be difficult to detect differences due to varying nutrient levels in the water. We used “rock wool,” but other suitable materials include vermiculite, perlite, and dried peat moss mix. All of these, other than rock wool, are available at local garden supply stores. The second suggestion is to use small (740 ml) bottles.


Now that you’ve built the components you need for the EcoColumn, try these activities to further your understanding. First, read the instructions and perform the activity. Then, for selected activities, view an example of our results in track our progress.

  • Taking Inventory and Pondering Change… Carefully describe living things, and predict changes in the system over time.
  • What’s on the Menu?… Use what you know about the organisms in your EcoColumn to create a food web.
  • Basically. I’m a Fungi… Observe and appreciate the diversity and abundance of these decay organisms, which can be found on almost every surface. [track our progress]
  • When it Rains… Use your EcoColumn to model the water cycle.
  • Decomposition Tea… Just how important is the process of decomposition to new life? [track our progress]

Taking Inventory and Pondering Change

The EcoColumn that you’ve designed includes a variety of aquatic and terrestrial organisms. In a study system like this, it’s important to describe the living things that you stock it with before you introduce them into their habitats. “Taking Inventory” will assist you in doing this, and “Pondering Change” will help you predict changes that you think will occur as your EcoColumn develops over time.

Materials Needed


Taking Inventory

  1. Assemble the aquatic and terrestrial (including compost) organisms to be introduced into your EcoColumn.
  2. Observe each item and identify with a common and/or scientific name.
  3. Using your Taking Inventory Data Sheet, describe identifying and interesting characteristics for each organism.
  4. Take and record measurements of each organism.
  5. Make a sketch of each organism, including scale.
  6. Make a graphic inventory of your EcoColumn, showing where each organism is to be placed.

Pondering Change

  1. Use your Pondering Change Data Sheet to make predictions about change in your EcoColumn over time.
  2. Decide the length of a study period for your EcoColumn.
  3. At regular intervals during your study period, observe your EcoColumn and record changes that occur.
  4. At the end of your study period, make another graphic inventory.

Activity Questions

At the start of your study period

  1. What organisms will you introduce into the aquatic habitat of your EcoColumn?
  2. What organisms will you introduce into your terrestrial habitat?
  3. What organisms will you introduce into your compost habitat?
  4. Which of these are producers? Consumers? Decomposers?
  5. How will the energy needs of these organisms be provided for?
  6. What do you expect to happen in your aquatic habitat over time? Your terrestrial habitat? Your compost habitat?
  7. How do you expect the components of each habitat to affect the other habitats?

At the end of your study period

  1. What types of changes occurred in your aquatic habitat? Your terrestrial habitat? Your compost habitat?
  2. What do you think caused these changes?
  3. How would you describe energy flow in your EcoColumn?
  4. How would you describe material cycling in your EcoColumn?
  5. What evidence, if any, indicated that the components of different habitats were affecting each other?
  6. How would you change the design of your EcoColumn for future studies of energy flow and material cycling?


What's on the Menu?

In the video for Session 7 (Energy Flow in Communities), we explored how energy enters and is transferred through the living world. You have designed your EcoColumn to include producers, consumers, and decomposers, which makes it an excellent system for the study of energy flow. In “What’s on the Menu?” you’ll use what you know about the organisms in your EcoColumn to create a food web.

Materials Needed


  1. Make a list of all of the organisms in your EcoColumn, including any “newcomers” that you’ve observed since you stocked the system. You may find it helpful to use your “Taking Inventory” Data Sheet (PDF).
  2. Using your What’s On The Menu Data Sheet (PDF), identify how each organism obtains energy.
  3. Distinguish the producers, consumers, and decomposers from one another.
  4. Use your Food Web Chart (PDF) to create the food web that exists in your EcoColumn.

Activity Questions

  1. In your EcoColumn, which organisms are the producers? The consumers? The decomposers?
  2. How does energy enter the community in your EcoColumn?
  3. How is energy transferred through the community?
  4. The following is the chemical reaction for photosynthesis:light energy + CO2 + H2O -> CH2O + O2

    light energy + carbon dioxide + water -> sugarPick an organism in your EcoColumn and use it as a physical model to describe how photosynthesis works.
  5. To which organisms is cell respiration important?
  6. The following is the chemical reaction for cell respiration: CH2O + O2 -> CO2 + H2O + energy>carbon dioxide + water + energy. Pick an organism in your EcoColumn and use it as a physical model to describe how cell respiration works.
  7. What is the relative importance of photosynthesis and cell respiration in your EcoColumn?
  8. Where do the decomposers fit in your food web?
  9. What happens to energy flow once it reaches the decomposers?
  10. Which organisms are the most important in energy flow in a community? Explain your answer.
  11. How is a constant supply of energy ensured in your EcoColumn?
  12. How does energy flow in your EcoColumn compare to energy flow in a natural community?


Basically, I'm a Fungi

Pronounced by some as “fun guy,” the fungi are part of the mostly microbial world of decomposers. Along with bacteria, fungi are responsible for the decay of dead things that would otherwise pile up around us. Basically, I’m a Fungi makes these organisms readily observable as cultures that grow on special materials — Petri plates that contain prepared media that act as a food source. This particular medium contains a relatively high amount of sugar, which favors fungi over bacterial cultures.

Two types of fungi may grow in your plates. Yeasts tend to grow into smooth, spreading circular colonies, while most molds will eventually develop into fuzzy growths. It’s not important that you identify which is which, just that you observe and appreciate the diversity and abundance of these decay organisms, which can be found on almost every surface.

Materials Needed


  1. When your Petri plates arrive, be sure not to open the lids. You’ll inadvertently introduce microbes if you do.
  2. To conserve media and make side-by-side comparisons, use a permanent marker to divide each plate into thirds on both the lid and the bottom.
  3. Select surfaces to be tested for the presence of fungi. A good variety will include soil, water, air (the inner surface of the bottle), plants, and animals.
  4. In each of the three Petri plates, write the name of one of the surfaces that you’re testing at the outer edge of the bottom side of the plate (the top may move around). Consider making one of the sections a “control,” which you do not disturb. The control can be used to make comparisons.
  5. Using a sterile swab for each surface, gently swipe the surface. Take care not to pick up debris.
  6. Open the appropriate Petri plate. Start at the outer edge of the appropriate section and make a streak in an “S” shape. Be sure not to press too hard and to keep your streak within section boundaries.
  7. Replace the lid and tape it closed.
  8. Turn each plate upside-down to avoid a “rain” of condensation from the lid as the colonies grow.
  9. Incubate in a warm place.
  10. Observe microbial growth in your plates over a two-week study period and record what occurs on your “Basically, I’m a Fungi” Data Sheet.

Note: It is safe to culture microbes in this way — they grow in a closed container and are types that are already present in the environment. To dispose of the plates, spray with disinfectant solution, seal, and throw away. The only thing to be careful about is opening the plate during your study — each time you do, you may introduce new microbes!

Activity Questions

Before you swab your plates:

  1. What are the distinguishing characteristics of fungi?
  2. Which surfaces do you think harbor these microbes?
  3. How do you think different surfaces might compare?

After your study period:

  1. What surfaces did you test for the presence of fungi?
  2. Describe the growth that resulted from testing these surfaces.
  3. How did different surfaces compare?
  4. Were you surprised by your results? Why?
  5. What can you conclude about fungal life in your EcoColumn?

TRACK OUR PROGRESS: Basically, I’m a Fungi

When It Rains...

It could be argued that the substance that is most important to the support of life is water. One of the reactants in photosynthesis — the chemical reaction that brings energy into the living world — is water. And, most cell processes must take place in the presence of water. Yet life relies on the physical environment for its water supply. Why doesn’t this water supply run out?

Along with other material cycles, the water cycle is essential to life on Earth. In “When It Rains…” you’ll use your EcoColumn to model the water cycle.

Materials Needed

  • Stocked EcoColumn
  • Ice water with ice in it
  • 20 cm of string or craft cord


  1. Remove the top unit of your EcoColumn and tie the string around the neck so that one end hangs freely.
  2. Invert the top of your EcoColumn over the terrestrial habitat.
  3. Add water with ice in it.
  4. Observe what happens over several hours.

Activity Questions

Water Cycle Concepts:

Evaporation — the change of state of water from a liquid to a gas (water vapor)
Transpiration — the evaporation of water from the surfaces of leaves
Condensation — the change of state of water from a water vapor to a liquid
Precipitation — water that falls in the form of rain, sleet, hail, or snow
Percolation — the flow of water through a substrate (e.g., soil)
Surface water — still or flowing water on the surface of the Earth
Groundwater — still or flowing water in the ground

  1. How is each habitat in your EcoColumn supplied with water?
  2. Within each habitat, how do organisms obtain their water?
  3. How would these habitats and organisms be supplied with water in nature?
  4. Does surface water exist in your EcoColumn? Groundwater? Explain your answer.
  5. What happened when you added ice to the inverted top of your EcoColumn?
  6. Which of the above concepts was illustrated by the addition of the ice?
  7. Make a diagram of your EcoColumn and use the water cycle concepts to label your drawing.


Decomposition Tea

In the video for Session 8 (Material Cycles in Ecosystems), the focus was on how the chemical elements required by living things are cycled between the living and nonliving environments. The action of decomposers is important in this process. Bacteria and fungi use the bodies of dead things for food, and in doing so, break down and release the chemical elements within. These become a store of nutrients for new generations of living things.

Just how important is the process of decomposition to new life? In “Decomposition Tea,” you’ll plant seeds and supply them with three different types of water: distilled water, fertilizer solution, and water taken from the aquatic habitat in your EcoColumn. We call this water “decomposition tea.”

Materials Needed

  • Stocked EcoColumn after 4-5 weeks.
  • Three Bottle Growing Systems planted with Fast Plant seeds in nutrient-free “soil”
  • One Light House (instructions from Brassica & Butterfly system)
  • One turkey baster
  • Distilled water (no nutrients)
  • Fertilizer solution (nutrient levels determined to promote optimum growth)
  • Decomposition tea (nutrients supplied by decomposition)
  • Decomposition Tea Data Sheet (PDF)

Note: You can use seeds of any type for this activity. We suggest Fast Plants because of their rapid life cycle and predictable growth habits under the controlled conditions in a Light House. “Decomposition Tea” is water extracted from the aquatic habitat of your EcoColumn after it has developed for several (approximately four to five) weeks.


  1. Build three Bottle Growing Systems. We used 740 ml water bottles as the smaller size works best for this activity.
  2. To each funnel, add material that is free or low in nutrients to act as soil. We used rock wool, which we purchased from Carolina Biological Supply Company (1-800–334–5551) or Vermiculite, perlite, or dried peat moss can also be used.
  3. Moisten the planting material with water.
  4. Plant an approximately equal number of seeds in each system (15 – 20). Try to distribute the seeds evenly within the system.
  5. Prepare fertilizer solution. Follow instructions on the container to make it full strength.
  6. Use a turkey baster to extract decomposition tea from the aquatic habitat of your EcoColumn. Replace the water you removed with untreated tap water.
  7. Add distilled water, fertilizer solution, and decomposition tea to different Bottle Growing Systems and apply appropriate labels.
  8. Place each system in a Light House so that the seeds sprout about 10 cm from the light. Adjust this distance to the top of the plants as they grow. Your study period begins at this point.
  9. Using your Decomposition Tea Data Sheet, track plant growth in each system for two weeks (or longer).
  10. Be sure to keep each system supplied with the appropriate type of water.

Activity Questions

Before the study period begins

  1. What plant characteristics might be affected by supplying different levels of nutrients in the water?
  2. What do you predict will happen to the plants grown in distilled water? Fertilizer solution? Decomposition tea?

After the study period ends

  1. What occurred during the study period to the plants in distilled water? In fertilizer solution? In decomposition tea?
  2. How do you account for any differences you observed?
  3. How does decomposition tea become a source of plant nutrients?
  4. How does this compare to what happens in nature?
  5. In the video, the nitrogen cycle was described. How does nitrogen cycle in your EcoColumn?
  6. Draw a diagram to show how nitrogen cycles in your EcoColumn.

TRACK OUR PROGRESS: Decomposition Tea

Track Our Progress

Get a glimpse of our system at various points in selected activites. Remember that every system is unique: don’t expect yours to look exactly like ours!

Series Directory

Essential Science for Teachers: Life Science


Produced by Harvard-Smithsonian Center for Astrophysics. 2003.
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  • ISBN: 1-57680-730-4