Problem 10

Background and context

• Anatomy. Species may share similar physical characteristics because this feature was present in a common ancestor (homologous structures).
• Molecular Biology. Genetic code and DNA represent the shared lineage of life. DNA comparisons can show how related species are.
•  Biogeography. The global distribution of fauna and the unique features of island species reflect evolution and geological change.
• Fossils. Fossils document the existence of now-extinct past species that are related to today's species.
• Direct observation. We can directly observe small-scale evolution in organisms with short life cycles (for example, insecticide-resistant insects).