Concepts of Biology (BIOL115) - Dr. S.G. Saupe (; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321

Evolution vs. Creationism: Some Case Studies

General Directions
     The following case studies describe situations that have been observed by biologists.  Biologists seek to understand and explain how these situations arose.  Read each case study and then describe how how each of the following individuals would explain it:  (1) Darwin - evolution via natural selection; (2) Lamarck - evolution via acquired characteristics; (3) a �scientific� creationist

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Case Study #1:  Mines, Grass & Wales
    The soils and workings (mining tailings) around mines in Wales are enriched in heavy metals such as lead, copper and nickel.  Populations of a small grass, Agrostis tenuis, are tolerant of toxic levels of these heavy metals.  However, other individuals of this same species of grass, growing on uncontaminated sites only a few meters away, cannot survive and grow on the tailings.  In fact, these sensitive individuals will die if transplanted to the site with tailings.  Likewise, individuals growing in the tailings will not grow well if transplanted to uncontaminated sites.  Heavy metal tolerance/sensitivity is inherited.  Explain why the grasses on the tailings can grow in the presence of heavy metals but grasses meters away cannot. 

Case Study #2:  Finches on the Galapagos Islands
    As you know, the Galapagos Islands are an archipelago (cluster of islands) off the coast of Ecuador.  These islands are volcanic.  Darwin and others have long noted that the species of finches that occur on the Galapagos are unique and occur no where else in the world.  However, these species are most similar to finches on the Ecuador mainland.  Explain why the Galapagos finches are unique yet similar in appearance to mainland ones.

Case Study #3:  Maize
     Maize (=corn) does not occur in the wild.  The only reason that it persists is because humans collect and plant its seeds from season to season.  Archaeological records show that the first cobs appeared about 10,000 ybp in Central America.  These early cobs were smaller than modern ones, but otherwise relatively similar.  Prior to 10,000 ybp no evidence has ever been found.  Explain how a new species such as maize could arise.

Case Study #4:  Crabs and Periwinkles

     This case study was provided on the handout in class.  Explain why the thickness of the periwinkle shells increased from 1850's to the present.


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