Evidence for Evolution

Evidence for Evolution

Evidence for evolution comes in...

• Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
• Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
• Biogeography. The global distribution of organisms 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 present-day species.
• Direct observation. We can directly observe small-scale evolution in organisms with short life cycles (e.g., pesticide-resistant insects).

What is Evolution?

• Evolution- a key unifying principle in biology, is a change in the genetic makeup (and often, the heritable features) of a population over time
• Two different types of evolution based on a scale are...
• Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups.
• Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.

What are Homologous Features?

• If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor.
• Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
• Some homologous features can only be seen in embryos.