GENETIC CHANGE IN A POPULATION OVER TIME

Types of evidence of evolution  Fossils  Homologies  Anatomical  Molecular  Developmental  Biogeography  Observable Events

Fossil Record Helps scientists understand pathway of evolution  Paleontology  Fossil Remains: ex. bone, tooth, or shell Traces: ex. burrow, footprint, or imprint

Fossil Record  Most fossils are found in layered sedimentary rock  Oldest fossils are in the lowest layer  Newest fossils are in the top layer

Fossil Record  Comparing fossils from different layers shows:  Life on Earth has changes  Increased number of life forms

Fossil evidence Reduction of toes over time

Anatomical Homologies  Homologous Structures: Similar structure but different function  Shows: Similar genes Common ancestor Turtle Alligator Bird Mammal

Anatomical Homologies  Vestigial Structure: Body part reduced in function in a living organism but may have been used in an ancestor  Shows: Organisms evolutionary past Whale pelvis & tailbone humans

Developmental Homologies  Shows: Similar genes Common ancestor

Fish, reptiles, birds, & mammals (yes, even us!) all have a tail, limb buds & pharyngeal pouches in the early stages of development Developmental Homologies

Molecular Homologies  DNA & the genetic code DNA codes for amino acids proteins “Universal” Genetic code The similarity in DNA shows:  A probable common ancestor for all life on Earth

Molecular Homologies  The amino acid sequence in a particular protein is compared between organisms. Number of differences from human hemoglobin

 Comparing amino acid sequence shows:  Closeness of relationship  A probable common ancestor Molecular Homologies

 Amino Acid Sequencing is probably the STRONGEST evidence for relationships among organisms. Amino Acid Difference in Hemoglobin Compared with Human Human hemoglobin has 146 amino acids SpeciesDifferenc e Gorilla 1 Rhesus Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125

What organism belongs at each branch?  CLADOGRAM: diagram that shows the evolutionary relationship among a group of organisms. Number of Amino Acid Differences G F E D C B A Common ancestor Where would the common ancestor be? Molecular Homologies

Biogeography  Geographic distribution  organisms living far apart may be similar because they share a common ancestor

Observable Events  Some changes in species have been observed and studied  Shows: Evolution is an ongoing process Peter & Rosemary Grant’s Study of Beak Size Shift in Darwin’s Finches H. Kettlewell’s Study of Peppered Moth Color Shifts