Overview: Students focus on the evolution of three species of lizards using real data sets – geographical and geological data, then morphology, and finally molecular data – to determine possible phylogenetic explanations. Author/Source: Filson, R.P. Grade level: 9-12 Time: Two full class periods Concepts: Biological evolution accounts for diversity over long periods of time. Traits that confer an advantage may persist in the population and are called adaptations. Speciation is the splitting of one ancestral lineage into two or more descendent lineages. Occupying new environments can provide new selection pressures and new opportunities, leading to speciation. Scientists test their ideas using multiple lines of evidence. Scientific knowledge is open to question and revision as we come up with new ideas and discover new evidence. Our knowledge of the evolution of living things is always being refined as we gather more evidence. Our understanding of life through time is based upon multiple lines of evidence. Scientists use the similarity of DNA nucleotide sequences to infer the relatedness of taxa. Scientists use anatomical evidence to infer the relatedness of taxa. Scientists use the geographic distribution of fossils and living things to learn about the history of life. Classification is based on evolutionary relationships. Evolutionary trees (i.e., phylogenies or cladograms) are built from multiple lines of evidence. Speciation is often the result of geographic isolation. Evolutionary trees (i.e., phylogenies or cladograms) portray hypotheses about evolutionary relationships. Scientists may explore many different hypotheses to explain their observations. Teacher background: Classification/Phylogenetics Speciation Evidence for Evolution

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