These explorations lead into a series of activities that focus on the fundamental life processes of information storage and its translation. Students examine the structure of DNA, and simulate the translation of DNA into protein. The evidence for the early evolution of life is the focus of the third lesson, History of Life on Earth . In addition to examining the fossil and rock records, students also explore the molecular evidence that can be found in modern day organisms. By comparing DNA and RNA, scientists have inferred relationships between current organisms and postulated a common, prokaryotic-like ancestor.
Students examine the aspects of the physical environment under which life began.
This lesson focuses on conveying not only what scientists know, but how they know what they know. In the concluding activity students construct a timeline that highlights the fact that most of life's history on earth has been in the form of single-celled organisms. Students explore some of the prevailing scientific ideas and the supporting evidence for them through readings and videotaped interviews of scientific experts. Students gain experience with the diversity of single-celled organisms through Winogradsky columns and microscope images. They then study the hypothesis for the evolution of cells with nuclei and other organelles, endosymbiosis, and the evidence for it.