Evolution Change over-time How does evolution happen? Natural Selection: o Variation caused by mutation o Environmental pressure o Selection of certain inheritable traits o Adaptation over many generations The Evidence for Evolution/ The evidence for a common ancestor The Fossil Record Anatomy & Embryology Biological Molecules The Fossil Record Fossil the remains or traces of an organism that died long ago Fossils show that different organisms appeared at different times and places on Earth What do you know about fossils? Rock Layers Transitional Species Missing link link between characteristics in past and present species Vestigial Structures Have no apparent function, but that resemble structures their presumed ancestors had. Examples: whales have pelvic bones, boa constrictors have hip and leg bones Embryology & Anatomy Anatomy the study of body structures of organisms Embryology the study of how organisms develop A. B. C. D. E. #1 A. B. C. D. E. #2 A. B. C. D. E. #3 A. B. C. D. E. #4 A. B. C. D. E. #5 A. B. C. D. E. Homologous Structures Similar structures that occur in different species that were inherited from the most recent common ancestor Example: forelimbs of vertebrates Analogous Structures Structures that have similar functions but do not come from the same ancestor. Example: wings Biological Molecules Biologists can compare DNA, RNA, amino acid sequences, proteins, and other biological molecules from many different organisms More similarities = more closely related Share a recent ancestor DNA Comparisons Human Chimpanzee Mouse A CG T Humans are 45% similar to black cottonwood tree 60% similar to chickens 85-89% similar to mice 98-99% similar to chimpanzees 99.8% similar to each other Gel Electrophoresis A technique that uses an electrical field within a gel to separate DNA by their size and charge. ABCD