Plastic sheet, pencils, and color markers -> concepts of contrast
Short lecture slides
Go over problems: worst question, virus and ribosomal RNA 85% correct.
Contrast demo using plastic sheets. Use color to demonstrate contrast.
Q: Why only anaerobic microbes exisit on Earth for the first 2 billion years?
Q: why is it incorrect to say that an object is partially sterile?
Summary of the class. Lessons learned.