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Destination: Galapagos Islands Cyber Field Trip

Cyber Field Trip Teaching Guide
Test the Earth: Soil Comparison Between the Galapagos Islands and Your Home

Student activity available at

This interactive activity will be available for students beginning Wednesday, December 9, 1998. Data from the Galapagos will be added Wednesday through Friday.

National Science Education Standards
Concepts and Terms
Safety Precautions
Critical Thinking Questions


Soil may be defined as the naturally deposited material that covers the Earth's surface and is capable of supporting plant growth and development. All life on Earth, including plants, animals and human beings, depends on soil for existence. Soil is formed as a result of natural decomposition processes that occur over extremely long periods of time. There are five basic factors involved in the formation of soil:
  1. material from which the soil is derived
  2. living organic matter
  3. climate
  4. slope and land form, or "relief"
  5. time
Natural soils vary greatly in their composition. Because soil formation requires a long period of time and all life depends on soil in some way, conservation and management of soil is critical. Soil testing, or analysis of soil composition, is a very important step in the conservation of soil.


5-8: Structure of Earth Systems
9-12: Energy in Earth Systems, Geochemical Cycles, Origin and Evolution of Earth Systems
5-8: Populations and Ecosystems
9-12: Interdependence of Organisms; Matter, Energy and Organization in Living Systems; Behavior of Organisms;


  1. To specify the importance of macronutrients in soil.

  2. To prepare an analysis of three important macronutrients found in your regional soil.

  3. To compare soil composition from different regions of the Earth, including the Galapagos Islands.


Macronutrients are elements required in very large quantities. There are six essential nutrient elements supplied through the soil: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S).

Nitrogen, which makes up 78% of the Earth's troposphere, is involved in virtually all biochemical processes that sustain plant and animal life. Free nitrogen is unusable by plants and animals and must be converted to other forms -- nitrates (NO3) and ammonia (NH3) -- in order to be utilized by plant tissues. This conversion is called "nitrogen-fixation" and is accomplished naturally by blue-green algae in aquatic ecosystems, by nitrogen-fixing soil bacteria found in the roots of legumes (beans, alfalfa, peas, clover, etc.) in terrestrial ecosystems, and by lightning in the atmosphere.

Phosphorus is essential for all animals and plants, and soil is a major source of this important macronutrient. Plants accumulate phosphorus directly from the soil, and animals ingest phosphorus by eating plants. Phosphorus is an essential component of nucleic acids, which are present in all living systems.

Potassium plays a vital role in the function of all plants. Some important benefits of potassium in plants are the prevention of disease and water loss; the prevention of wilting from loss of turgor pressure; the enhancement of fruit size, development and flavor; the production of amino acids, which are utilized in protein synthesis; the formation of chlorophyll; and the transportation of starch and sugar throughout plant tissues.

Another important factor in soil is pH, which controls how well plants utilize soil nutrients, such as P, K and N. All plants have a pH preference -- for example, many cacti and succulents thrive in soils that are slightly acidic and have pH values between 5.0 and 6.0.

Temperature is one of the most important physical factors in the environment of any organism. Soil-dwellers make use of the physical characteristics of soil to regulate their temperature. Organisms in the soil play an integral role in the stability of ecosystems. In a single handful of topsoil, bacteria and other decomposer microorganisms are found by the billions! These organisms recycle nutrients by breaking down complex organic compounds found in the upper soil layers. By doing so, these organisms return vital nutrients to the soil that are necessary for plant and animal growth.


  • Three clean milk containers, cut in half
  • Soil test kit*
  • Air thermometer
  • Soil thermometer*
NOTE FROM SHERRI: You can use any soil test kit that performs nitrogen, phosphorus, potassium and pH tests, such as a Rapitest, which can be found at your local nursery. Lab-Aids Kit: Chemical Composition of the Soil is a quick, easy and safe soil test kit that can be purchased from any biological supply. LaMotte Soil Science Field Testing Outfit (model AM-31) is the best all-around soil test kit for the field. It includes materials for 50 soil tests for pH, nitrogen, phosphorus and potassium, and refills are available. It can be ordered from LaMotte Chemical, 800-344-3100. Microorganisms in the Soil Kit are available from Science Kit and Boreal Laboratories, 800-828-7777. Soil thermometers are inexpensive and can be purchased from a garden center or biological supply company.

Any soil analysis kit that reports its values as "pounds per acre" (PPA) should be converted to parts per million (PPM). The conversion is 2 PPA=1 PPM.

In general, soil testing is a great way to introduce scientific field testing in chemistry, biology, geology, physical science, as well as environmental science. Soil testing equipment is relatively inexpensive. Your regional Environmental Protection Agency office is a great source of information and often can provide guest speakers for your classes. Another great source of information on soils is your local Soil Conservation District.


  • Wear safety goggles when handling chemicals
  • Take precautions against poisonous, stinging or biting animals/insects in the field
  • Follow all laboratory and field safety regulations!


  1. Identify three different areas of your school grounds or garden from which you will collect soils. Make notes regarding the environmental conditions of the area from which you will collect sample, e.g., "collected on the damp side of the tool shed"; "by the roots of the shady oak"; "on the edge of the pond about 5 feet from the water, lots of gnats"; "sunny, dry spot in the middle of the field"; etc. Record this data in the Soil Analysis Data Chart observations section.

  2. Before taking the soil samples, measure and record the soil temperature and the air temperature right above the soil. Record this data in the Soil Analysis Data Chart temperature sections.

  3. Using the milk containers, collect about a half of a deciliter (approximately one pint) of soil from each of the three different areas.

  4. Following the directions of your soil test kit, analyze the soil samples for levels of nitrogen (N), potassium (K) , phosphorus (P) and acidity (pH). (Sherri will be using the LaMotte Soil Science Field Testing Outfit, model AM-31.)

  5. Record the values for all three samples of each test in the Soil Analysis Data Chart.

  6. Click the "chart my data" button to compare your data to the Galapagos Islands soils collected and measured by Sherri. (Data from samples will be added from Wednesday, December 9, through Friday, December 11, 1998.)


  • Based on your soil analysis and that of the Galapagos Islands, do you think a relationship exists between soil and temperature? If so, what is it?

  • What differences in macronutrient levels exist between your environment and that of the Galapagos Islands? Between different islands of the Galapagos?

  • Based on your findings, create a hypothesis about the differences between (a) local and Galapagos Island soils and (b) soils from island to island.

  • Are there differences in the pH levels of the soil samples? What factors might lead to these differences?

  • Is it useful to present your data or the Galapagos Islands data as averaged values, rather than as individual measurements? How do the data support your conclusions?


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