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Theory of Evolution Evidence of Evolutionary Change Vocabulary Words 1. Evolution- change over time; the process by which modern organisms have descended from ancient organisms. 2. Fossil- preserved remains or traces of ancient organisms. 3. Homologous structures- structures that are similar in different species of common ancestry. 4. Vestigial structure- structure that is inherited from ancestors but has lost much or all of its original function 5. Analogous Structures- Body parts that share a common function but not structure 6. Biogeography- The study of where organisms live now and where they and their ancestors lived in the past Where did Darwin get his ideas? Darwin made several observations when formulating his theory of evolution. These observations were based on the following concepts: 1. 2. 3. 4. 5. The Fossil Record Biogeography Comparative Anatomy Comparative Embryology Molecular Biology (Genetic Code) The Fossil Record • Fossils are evidence of deceased organism from their preserved remains retained by the earth • There are several layers of the earth which fossils are found in • Law of Superposition: What about the fossils changes as we dig deeper into the layers of the earth? Biogeography Pangaea was the time when the continents were all connected as one large land mass Due to plate tectonics, this united large landmass progressively separated into several continents The separation of the landmass also separated populations of organisms Biogeography: the study of where organisms live now and where they and their ancestors lived in the past Comparative Anatomy What do a chicken and a human have in common? What do a shark and a dolphin have in common? You probably first thought to compare physical structures of each species Comparative anatomy compares the physical, anatomical structures of species to understand their ancestral relationship Homologous structures: Structures that are shared by related species and have inherited from a common ancestor Human Cat Whale Bat Each of these organisms have similar bone structures that modified through evolution, yet still resemble descent from a common ancestor Comparative Anatomy Cont’d Bats and bee’s both have wings Is there a major difference between the wings of a bird and the wings of a bee? Do they do the same thing for each organism? Structures that are similar in unrelated species are called Analogous Structures • They do not have common ancestry… so why do you think they have similar structures? • What can studying analogous structures tell us about the evolution of certain animals? Vestigial Structures • Some homologous structures have lost most or all of its function but still are present in some organisms • For example, our appendix does not serve a significant function in our bodies • Vestigial Structures: structures inherited from ancestors but have lost much or all of its original function due to selection pressures. Watch Hank Green’s Vestigial structures video Comparative Embryology According to Comparative Embryology, All vertebrate embryos follow a common developmental path due to their common ancestry How does this support the theory of evolution? Lizard Turtle Pig Human Molecular Biology Recent evolutionary research is heavily focused on studying ancestry at the molecular level • Genes • DNA • Molecules We can now compare the patterns found in the genetic code and homologous molecules in different species to help understand the missing links in evolutionary evidence A Common Genetic Code All living organisms are governed by the same GENETIC CODE which is based on the sequence of bases found in DNA molecules DNA is composed of sequences of 4 different nucleotide based Guanine (G) Adenine (A) Tyrosine (T) Cytosine (C) The sequences and amounts of where these bases occur differentiate proteins within organisms NOVA- Bird Brains Investigate how molecular biology can help understand the evolutionary relationship between two organisms such as Humans and Birds Watch Bird Brains Complete Bird Brains Activity Bird Brains Follow Up Activity • The protein Cytochrome C is found in many different species • Different species have different DNA sequences which produce different sequences and amounts of amino acids within proteins • Find the differences in the cytochrome C protein of several organisms, comparing it to the Human Cytochrome C protein • PREDICT: which organism do you think will be more closely related to humans based on this molecular evidence?