Clues About EvolutionClues About Evolution

Chapter 6, Section 2Chapter 6, Section 2

Support for EvolutionSupport for Evolution

FossilsFossils– Remains or traces of organisms found in Remains or traces of organisms found in

sedimentary rock.sedimentary rock.– Provide an incomplete record of changes that Provide an incomplete record of changes that

have occurred in organisms and in the have occurred in organisms and in the climate.climate.

Support for EvolutionSupport for Evolution

FossilsFossils– Dating a fossil:Dating a fossil:

Relative DatingRelative Dating– Gives an estimated date based on ages of rock layers Gives an estimated date based on ages of rock layers

above and below the fossil.above and below the fossil.

Radioactive DatingRadioactive Dating– Gives an exact date by comparing the amount of Gives an exact date by comparing the amount of

radioactive element in a rock with the amount of the radioactive element in a rock with the amount of the stable element.stable element.

Support for EvolutionSupport for Evolution

EmbryologyEmbryology– Study of the development of embryos (earliest Study of the development of embryos (earliest

stage of a life form).stage of a life form).Example:Example:

– All vertebrates at some point have both gills and a tail.All vertebrates at some point have both gills and a tail.

Support for EvolutionSupport for Evolution

Homologous Structures:Homologous Structures:– Structures that are similar in structure and Structures that are similar in structure and

origin (and sometimes function).origin (and sometimes function).Example:Example:

– Human arm, bat wing, and a dolphin flipper.Human arm, bat wing, and a dolphin flipper.

Support for EvolutionSupport for Evolution

Vestigial StructuresVestigial Structures– Structures that appear to have no function.Structures that appear to have no function.

Examples:Examples:– Appendix, pelvic bones of snakes and whales.Appendix, pelvic bones of snakes and whales.

Support for EvolutionSupport for Evolution

DNADNA– Similarities in DNA can suggest similar Similarities in DNA can suggest similar

ancestry. ancestry.

Support for EvolutionSupport for Evolution

Direct Observations:Direct Observations:– Antibiotic resistant, selective breedingAntibiotic resistant, selective breeding