A collection of images shows the diversity of eyes found in the natural world, and it's explained how eyes are a product of natural selection that evolved for best use. It is explained how these diverse eyes work; from the simple collection of light-sensitive cells in an earthworm, to the indented cells in a nautilus and onto eyes that possess lenses. The differences are clearly shown using practical models, including the pinhole camera at the Greenwich Observatory.
Students could explain in their own words how the physiology and effectiveness of eyes of an earthworm and a nautilus differ. They could then be asked to explain how the lens might have evolved.