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Darwin's Eden

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Letter from Alan Alda

Related Sites for Voyage to the Galapagos
in the classroom
TEACHING GUIDES


Voyage to the Galapagos:
"Darwin's Eden"


Our journey begins on the island of Espanola, where host Alan Alda comes face to face with a land iguana. When Charles Darwin visited here in 1835, differences he observed in iguanas, tortoise shells, finches and other unique species became the first clues for developing his later theories of evolution and natural selection.

Curriculum Links
National Science Education Standards
Activity: Backyard Chemistry




CURRICULUM LINKS


BIOLOGY/
LIFE SCIENCE


biodiversity, evolution

EARTH SCIENCES


ecosystems

GENETICS

 

GEOGRAPHY


archipelago, equator

SOCIAL STUDIES

Latin America

(Please visit the Subject-Area Search feature on this website for related Frontiers shows and activities!)



NATIONAL SCIENCE EDUCATION STANDARDS

SCIENCE AS INQUIRY / LIFE SCIENCE
5-8: Structure and Function in Living Systems; Reproduction and Heredity; Populations and Ecosystems; Diversity and Adaptations of Organisms
9-12: Molecular Basis of Heredity; Biological Evolution; Interdependence of Organisms; Matter, Energy and Organization in Living Systems; Behavior of Organisms
EARTH & SPACE SCIENCE
5-8:
Structure of Earth's Systems
9-12: Origin and Evolution of Earth's Systems
SCIENCE IN PERSONAL AND SOCIAL PERSPECTIVES
5-8: Populations, Resources and Environments
9-12: Natural Resources
HISTORY AND NATURE OF SCIENCE
5-8,
9-12:
Science as a Human Endeavor; Nature of Science/Scientific Knowledge



ACTIVITY: BACKYARD CHEMISTRY

The igneous islands of the Galápagos are relatively young, in geologic time. Over millions of years, the barren rock of the new islands decomposed to form soil. Heat, cold, glacial movements, rain and other factors can all influence soil formation.

As farmers and gardeners know, soil chemistry is critical. The degree of acidity or alkalinity of soil is measured in terms of pH. Plants need the correct pH to thrive and utilize nutrients. Some plants fare better in acid soils, others in alkaline. Use a soil testing kit to find out what the pH values are in different regions of your yard at home or in the school garden area.

As important as soil chemistry is, water is perhaps even more vital in sustaining life. Because the Galápagos Islands are located in the Pacific Ocean, 600 miles from the nearest mainland, the quality of the Galápagos waters is integral to the survival of the islands' wildlife. Like soil, water holds dissolved nutrients that affect the organisms dependent upon the water supply.

  • The pH value expresses the degree of activity in an acid or base in terms of hydrogen ions (hence the H in pH). pH can be measured on a scale from 0 to 14. A pH value of 7 is neutral; less than 7 represents acid substances; higher than 7 represents base or alkaline substances. The pH of soil determines how well the plants utilize nutrients like phosphorus, potassium and nitrogen.

  • To conduct specific pH tests, use pH paper, a meter or an electronic probe.

After testing your soil and water, visit the Destination: Galapagos Islands website to compare your data with data from tests conducted by the Frontiers team during their visit to the Galápagos in December 1998.

MATERIALS
  • soil thermometer
  • small empty milk cartons or other clean containers
  • pH paper, meter or other testing devices (garden centers sell soil testing kits)
  • soil samples from various sites
  • water samples from various sources (tap, pond, bottled, rainfall)
Note: You can find information on soil test kits and supplies at the "Test the Earth" activity on the Destination: Galápagos Islands website.

SOIL TESTING PROCEDURE

  1. Decide what factors you want to test. Set up charts and tables to enter your data.

  2. Collect soil from three or more different locations: various spots from your yard at home, the school yard or garden, and another site, such as a wetlands area. You could also test and compare clay soil, top soil and beach sand.

  3. Use the soil thermometer to take the temperature of different soils and compare.

  4. Test soil samples with the pH kit. Once you have taken the pH values, try to figure out reasons for the results.

  5. Use a soil testing kit to analyze soil for levels of nitrogen, phosphorus and potassium.

  6. Compare and analyze data. Graph the results.

  7. After gathering your data, visit the "Test the Earth" activity on the Destination: Galápagos Islands website, where you can compare your results with data on soil in the Galápagos. Look for the interactive graphs in this activity, which will help you analyze results.

WATER TESTING PROCEDURE

  1. Decide what factors you want to test. Set up charts and tables to enter your data.

  2. Use pH paper or a test kit to conduct comparative studies of water from various sources.

  3. Compare and analyze data.

  4. After gathering your data, visit the "Water World" activity on the Destination: Galápagos Islands website, where you can find out how to test for salinity and dissolved oxygen and compare your results with data on water in the Galápagos. Look for the interactive graphs in this activity, which will help you analyze results.
EXTENSIONS

  1. What importance would pH value have for hydroponic plants grown in water?

  2. Find out more about the geologic history of your region. How was the land formed? Was it affected by glaciers? Was it under water at one time? How did the natural history affect the soil?

  3. Set up an experiment to measure the effects of acid rain where you live.

  4. Compare the pH values of bottled waters and rain water.






 

Scientific American Frontiers
Fall 1990 to Spring 2000
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