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What Scientists Agree On – Earth is about 4.6 billion years old – Life has inhabited Earth for most of its history – All organisms living today have evolved from earlier, simpler organisms Evidence #1 Pg. 45 Fossils • Preserved remains or imprints of an organism – Remains include bone, teeth, or shells Fossils Fossilized species in older rock are simpler from those found in newer rock 140 million years 800 million years Intermediate Fossils • “Transitional fossils” link the older and newer species • Many have been found: – Fish and Amphibians – Dinosaurs and Birds – Reptiles and Mammals Intermediate Fossils • In 1990, transitional whale fossils were discovered • Evidence shows that whales evolved from 4legged land mammals Whale Example Why We Don’t Have More Fossil Clues • Fossils only form when the conditions are right! • Most common in streams, lakes, shallow seas, and near volcanoes Why We Don’t Have More Fossil Clues • Even if the conditions are right sometime the body plan is not! – Exoskeleton vs. soft body VS. Evidence #2: Pg. 46 Anatomy Development • Comparing different body structures between species suggests relatedness a. Homologous Structures • Different functions but same bones/structures • These organisms likely evolved from a closely related common ancestor b. Analogous Structures • Same functions but different bones/structures • These organisms likely evolved from distantly related ancestors c. Vestigial Structures • Structures that are present but are no longer needed for survival Tailbone Tonsils Appendix Evidence #3 Pg. 47 Biological Molecules Contain Evolutionary Record • If species change over time, so does the genetic material • Study proteins and DNA code for clues Proteins • Your DNA code determines what proteins are being made in your cells • Your proteins determine what you look like! • Proteins are made up of chains of amino acids • Closely related = similar amino acids = similar proteins Cytochrome C Protein Relationship to Humans Species Protein Differences Gorilla 1 Rhesus Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125 Evidence #4: • Closely related species have more similar embryo development Pg. 46 Embryo Development • Closely related species have more similar embryo development
