Evidence of Evolution

1.Fossil Record 2.Homologous Body structures 3.Similarities in Embryology 4.Biochemical Evidence

Evidence of Evolution: The Fossil Record Fossil record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

Relative vs. Absolute Dating

Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Drawbacks – provides no info about age in years

Absolute Dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain Drawbacks - part of the fossil is destroyed during the test

–A half-life is the amount of time it takes for half of the isotope to decay. Radiometric dating uses decay of unstable isotopes. –Isotopes are atoms of an element that differ in their number of neutrons.

Primate Fossils AustralopithecusHomo erectusHomo sapien

Primate Bone Structure

Evidence of Evolution: Homologous Body Structures – Structures that have different mature forms but develop from the same embryonic tissues Ex: Wing of bat, human arm, leg of turtle Turtle Alligator Bird

Evidence of Evolution: Homologous Structures Features that are similar in structure but appear in different organisms and have different functions. Strong evidence for common ancestor. Ex: forelimbs of humans, bats and moles. Human hand Bat wingMole foot

Analogous Structures Structures that perform a similar function. Not evidence of common ancestry.

Vestigial Structures Remnants of organs or structures that had a function in an early ancestor. Ex: Ostrich wings, used for balance but not flight Ex: Humans’ appendix

Evidence of Evolution: Similarities in Embryology In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

Embryological Development

Evidence of Evolution: Biochemical Similarities Scientists study nucleotide sequences in DNA and proteins in different organisms to determine ancestry. If the organisms are closely related they will have similar sequences of nucleotides in their DNA and arrangement of amino acids in proteins.

Evidence of Evolution: Biochemical Similarities OrganismAmino Acid Differences OrganismAmino Acid Differences Human beta chain0Mouse27 Gorilla1Kangaroo38 Rhesus monkey8Chicken45 Dog15Frog67 Cow25Soy bean124 The more similar the amino acid sequence, the more closely related the organisms are.