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I have been teaching selection and adaptation as the driving forces of evolution. When we are discussing the electron transport chain my senior biology students ask how did the electron acceptors get in this order of increasing electronegativity. My answer is always that these molecules did not get in the order nor were they placed in this order, rather the order was an accident of trying different possibilities. The arrangement we see now is the one that worked. We don't know how many different variations existed that did not survive. After this morning's discussion about Paul's story of evolution being change, diversity, and explanation, I plan to change my approach to their questions. The evolution challenge game created an aha moment for me that sent shivers through my brain- yes, I felt them!

In October, when we study cellular respiration, I will be ready. Mitochondrial organization, as we see it now, came out of randomness. The electron acceptors developed through a system of randomness leading to diversity. The environment, fine and coarse, selected for certain acceptors. The acceptors embedded in the inner mitochondrial membrane randomly into a diversity of arrangements. The arrangement that lead to the most opportunities for the creation of a proton gradient to drive the phosphorylation of ADP into ATP and result in the source of kinetic energy that permitted cell work for life was selected for until adaptation eliminated diversity into the arrangement of electron acceptors by increasing electronegativity. The need for a large energy source in a eukaryotic cell was the selective pressure that reduced diversity and resulted in order.

The class will then take the environmental challenge. The students will see the randomness leading to diversity. We will impose a selective pressure so that the students can see that adaptation will reduce diversity. Next we will participate in the National Geographic Genographic Project. We will compare our individual results to again see that the diversity of human life that migrated out of Africa was selected upon by the different environments into which people travelled. The different environments put selective pressure on the migrating groups that caused adaptations with a resulting decrease in diversity. It was the reduction in diversity that resulted in a unique genetic marker for humans in each path of migration. The uniqueness of these markers permitted the tracing of humans as they populated the Earth.

A new idea for next year's biology discussion. Thanks, Paul.