Science with Kids: Ecosystem in Miniature, Part 2
Now that your bottle ecosystem is ready and hanging, it's time to talk real science.
If you missed Part 1, please find instructions on how to make your own ecosystem in a bottle here.
Experimenting with the Ecosystem
Encourage your kids to examine how soil, water, and plants interact under the conditions you create together by choosing one of the many options:
You can fill the deep funnel with the soil
- collected from a local area;
- bought in a gardening store.
Fill the bottom reservoir with
- tap water;
- water from a local pond or river;
- water from your fish tank;
- or even water from a puddle!
You can pick any plant seeds, but the ones that germinate and grow fast will be the best choice for registering change:
- lawn mixes grow faster;
- prairie grass has roots that are more interesting to observe;
- beans are easier to obtain, make sure you soak the seeds overnight before you plant them.
The seeds you plant into the deep funnel will sprout up and grow depending on the nutrients they take from the soil and the quality of water from the bottom reservoir:
- The water and soil you collect from a local area are very likely to contain other plant seeds algae, insect larvae, or phytoplankton.
- Tap water and store-bought soil are more "sterile" in this respect.
And since the best method of experimenting is comparison, you'd better make two hanging bottles create different conditions and observe the differences in plant growth that they cause.Create Conditions
You can create completely different conditions like:
- collected water+collected soil vs tapwater+store-bought soil;
- vary only one component and see how the slight change affects the whole system;
- use the same components but vary the treatment, e.g.: add fertilizers and see if they drive algae in the bottom reservoir to grow.
The choice of experimenting options is literally endless, and it may be at times difficult to choose what to study. Start with formulating the question you'd like to get an answer to and see what changes you need to introduce to get it.
You can operate a number of variables to make your experiments more versatile:
- Amount and type of water, soil, and seeds;
- Additional substances (pollutants or fertilizers);
- Way of treatment: additional substances can be applied to the water, soil and/or plants they can be added at different stages, etc.
- External factors: the amount of light, type of light, temperatures or even sounds - you can grow your ecosystems to particular tunes and see which melody promotes faster growth.
Note: keep your experiment simple. Don't change too many variables at a time; otherwise, the results will be confusing.
How to Measure Effects
To draw actionable conclusions from your experiment, look for indicators. These are the characteristics of your ecosystem that are susceptible to change in association with different variables.
You can look for indicators in plants:
- the number of seeds that actually sprout;
- how high or leafy they grow;
- how thick their stems are, etc.
and water-soil system:
- the growth or decrease of the algae population;
- the clearness of the water, etc.
Ask your kids to register every change in a special logbook, if they can write or ask them to formulate the entries and write them down yourself. Log measurements, take photos, draw schemes, etc. In other words, do everything that will make your kids feel like actual scientists!
Miniature Ecosystem Sample Experiment
Below you will find a sample experiment procedure. Follow it to take your first experiment and then, let your creativity loose!
Many US states use salt to remove ice from roads. The choice of salt varies from state to state but the most frequently used substances are sodium chloride (NaCl) and calcium chloride (CaCl2).
Sodium chloride dissolved in melt-water produces an effect on plants growing near the road.
- What effect does salted melt-water produce on plants?
- What concentration of NaCl in the melt-water produces the effect?
We will examine:
- The growth of plants in bottle ecosystems with different concentrations of NaCl in the bottom reservoir water.
The following variables will remain the same for all ecosystems involved in the experiment:
- Type and amount of soil;
- Type and amount of water;
- Plants (type and age);
- Watering schedule;
You will need:
- 4 hanging bottle ecosystems with equal amounts of soil in the deep funnel and 50 ml of water in the bottom reservoir;
- 4 blank labels;
- Grass or other fast-growing plant seeds;
- Road or kosher salt. Don't pick table salt - it may contain iodine, which can affect the overall results of the experiment.
- Glass dropper/
- Optional: pH testing kit.
- Plant the seeds in the 4 ecosystems. Let them germinate.
- Label the ecosystems: 5.0% NaCl, 1.0%NaCl, 0.1% NaCl, and Control.
- Prepare salt solutions: dissolve 1/10 gram of salt in 100 ml water for the 0.1% solution 1 gram for 1.0% solution, and 5 grams for 5.0% solution.
- Feed each plant 10 ml of the solution that corresponds to its ecosystem label. For the Control ecosystem, add plain water.
- Rely on the schedule to feed the plants regularly. You may schedule salt treatment on every fourth day or choose another frequency.
- Take measurements to log plant development: plant height, number of leaves, their size and color. Take photos, if desired, to track changes.
- Optional: test soil pH.
- In a month, draw conclusions to see if the results support your hypothesis.
- Optional: Repeat the experiment to prove the validity and stability of the results.
Help your kids out with the experiment. Don't push; help them monitor and record changes and write a scientific report with pictures afterward or maybe issue your own one-time journal! Who knows, maybe this simple experiment will inspire your child to change the world!
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