KEY CONCEPT Evidence of common ancestry among species comes from many sources.

Evidence for evolution in Darwin’s time came from several sources. Fossils Geography Embryology Molecular Biology Anatomy

Fossils Fossils – preserved remains or markings left by organisms that lived in the past Fossils provide evidence of evolution. Fossils in older layers are more primitive than those in the upper layers.

Fossils Fossil record – the chronological collection of life’s remains in sedimentary rock layers.

Transitional forms are links between modern animals and ancient. Mesonychilds are the hypothesized link between modern whales and hoofed mammals.

Geography The study of geography provides evidence of evolution. Island species closely resemble nearest mainland species Populations show variation from one island to another Different plants, climates, and predators favored different traits in the population

Embryology provides evidence of evolution. Identical larvae, different adult body forms Similar embryos, diverse organisms Larva Adult barnacle Adult crab

Embryology Embryology provides evidence of evolution. Embryos of fish, birds, reptiles, and mammals are all similar They all have gill slits which develop into gills in adult fish and ears and throat in mammals Molecular Biology DNA and protein sequences are similar between related organisms

Anatomy The study of anatomy provides evidence of evolution. Homologous structures are similar in structure but different in function. Homologous structures are evidence of a common ancestor.

The study of anatomy provides evidence of evolution. Analogous structures have a similar function. Analogous structures are not evidence of a common ancestor. These species evolved separately They faced similar environmental challenges and developed similar solutions Human hand Bat wing Mole foot Fly wing

Vestigial structures are remnants of organs or structures that had a function in an early ancestor. Ostrich wings are examples of vestigial structures. Examples in humans- appendix and coccyx (tail bone)