Paul Andersen explains how variation is created within a cell. He starts by showing how molecular variation can increase fitness at the local level. He explains how an additional chlorophyll molecule allows plants to absorb more light from the sun. He also explains how cells can vary the composition of phospholipids in their cell membrane. He explains the significance of heterozygote advantage and how gene duplication can create novel genes. The antifreeze protein evolved from a simple digestive protein.