With an often unexpected outcome from a simple experiment, students can discover the factors that cause and influence thermohaline circulation in our oceans. In two 45 minute class periods, students complete activities where they observe the melting of ice cubes in saltwater and freshwater, using basic materials: clear plastic cups, ice cubes, water, salt, food coloring, and thermometers. There are no prerequisites for this lesson but it is helpful if students are familiar with the concepts of density and buoyancy as well as the salinity of seawater. It is also helpful if students understand that dissolving salt in water will lower the freezing point of water. There are additional follow up investigations that help students appreciate and understand the importance of the ocean’s influence on Earth’s climate.

This lesson introduces students to the concepts of evolution, specifically the evolution of humans. So often our students assume that humans are well adapted to our environments because we are in control of our evolutionary destiny. The goal is to change these types of misconceptions and get our students to link the concepts learned in their DNA, protein synthesis, and genetics units to their understanding of evolution. Students will also discover that humans are still evolving and learn about the traits that are more recent adaptations to our environment. The lesson is designed to take two one-hour class periods to complete. The activities will allow students to draw connections between environmental pressures and selected traits, both through data analysis and modeling. Most activities can be done without any special materials, although the Modeling Natural Selection activity needs either a tri-colored pasta, or tricolored beans, to be completed effectively.