Structure, Function, and Information Processing

Problem 265: Estimating Maximum Cell Sizes Students estimate tyhe maximum size of spherical cells based on the rates with which they create waste and remove it through their cell walls. [Grade: 11-12 | Topics: differential calculus, unit conversion]

Matter and Energy in Organisms and Ecosystems

Problem 63 Solar Activity and Tree Rings - What's the connection? - Trees require sunlight to grow, and we know that solar activity varies with the sunspot cycle. Can an average tree sense solar activity cycles and change the way it grows from year to year? This activity uses a single tree to compare its growth rings to the sunspot cycle. This is also an interesting suggestion for science fair projects! Here is the accompanying Excell Spreadsheet Data File. [Grade level: 4-6 | Topics: Spreadsheets and technology; decimal math]

Growth, Development, and Reproduction of Organisms

Problem 392: Exploring the DNA of an organism based upon arsenic. Students estimate the increase in the mass of the DNA from an arsenic-loving bacterium in which phosphorus atoms have been replaced with arsenic. [Grade: 8-10 | Topics: integer math; percentages] (PDF)