Evidences of Evolution

Genetic change in a population over time Evolution Genetic change in a population over time Population Dynamics POPULATIONS IN ECOSYSTEMS

Charles Darwin On his journey around the world, Darwin found evidence of gradual change (evolution). Darwin cited evidences he found in fossil records, homologous structures, and geographic distribution.

Evidences of Evolution Today most evidences for evolution are grouped into five main categories: Fossil Record Biochemical Comparative Anatomy Biogeography Observable Events

Fossil Record Paleontology- the study of fossils Fossils – remains or traces of organisms that lived long ago Remains: ex. bones, teeth, or shells Traces: ex. burrows, footprints, or imprints Photos by cbray

Most fossils are found in layered Fossil Record Most fossils are found in layered sedimentary rock Layers diagram by cbray Oldest fossils are on the lowest layer

Fossil Record The fossil record is incomplete Some environments are less likely to cause fossil formation Bodies of some organisms decay faster than others The fossils that have formed present strong evidence that evolution has taken place Relative and radiometric dating

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

Biochemical Evidence Universal Genetic Code Triplets of DNA nitrogen-base sequences that code for specific amino acids The similarity of triplet DNA codes making-up amino acids shows: a probable common ancestor for all life on Earth Genetic code table by cbray

Number of differences from human hemoglobin Biochemical Evidence Amino Acid Sequencing The amino acid sequence in a particular protein is compared between organisms. Species that have few differences are thought to have shared a common ancestor more recently. 8 125 45 27 Amino acid differences designed by cbray (with PPT clip art) 67 1 Number of differences from human hemoglobin

Amino Acid Difference in Hemoglobin Compared with Human Biochemical Evidence Amino Acid Sequencing is probably the STRONGEST evidence for relationships among organisms. Amino Acid Difference in Hemoglobin Compared with Human Species Difference Gorilla 1 Rhesus Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125 Amino acid differences chart by lpriddy Human hemoglobin has 146 amino acids

Number of Amino Acid Differences Amino Acid Difference in Hemoglobin Compared with Human Biochemical Evidence Species Difference Gorilla 1 Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125 Cladogram: diagram that shows the evolutionary relationship among a group of organisms. B A C D Number of Amino Acid Differences 150 100 50 40 20 30 10 Where would the common ancestor be? What organism belongs at each branch? E F Amino acid differences chart by lpriddy G Common ancestor

Ancient lobe-finned fish Comparative Anatomy Homologous structures- structures that share a common ancestry; similar structures with different functions Turtle Alligator Bird Mammal Ancient lobe-finned fish Homologous structures show: an organism’s evolutionary past and common ancestry

Comparative Anatomy Vestigial structures- structures that are present but diminished in size or function Vestigial structures show: an organism’s evolutionary past a common ancestor with species that have similar structures that are still functioning Examples: Human tailbone, snake pelvic bones and limb bones, and some cave-dwelling salamanders have eyes even though members of the species are completely blind.

Comparative Anatomy Embryology- embryos of different species may appear similar in early stages of development Example: vertebrate development Tail buds and pharyngeal pouches Embryo drawings by cbray

Comparative Anatomy Comparison of similarities in embryos can show: relationships to a common ancestor Embryo drawings by cbray

Geographic Distribution of Organisms Biogeography Geographic Distribution of Organisms Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara Organisms living widely apart (even different continents) may be similar because they share a common ancestor

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