Evidences of Evolution

Evolution Genetic change in a population over time

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

Most fossils are found in layered sedimentary rock 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 Fossil Record

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

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

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. Number of differences from human hemoglobin

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

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

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

Comparative Anatomy Comparison of similarities in embryos can show: relationships to a common ancestor

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

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