Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Macroevolution Website: http://evolution.berkeley.edu/ Descent with modification as a theory One of the strengths of a theory is that it can be tested using independent lines of evidence 1 Fossil record provides snapshots of the past remains of organisms or signs of organisms preserved over time Shows different life forms and also clues to the way they lived Fossil record supports descent with modification If one species descended from another: Fossils should show an ordered pattern (through time one form is replaced by similar but different forms) EVIDENCE Fossil record shows that organisms have appeared in an ordered and consistent sequence Fossils that show the intermediate states between an ancestral form and that of its descendants, are called transitional forms example: Tiktaalik 2 Do gaps on the fossil record disprove evolution? Fossils link ancestral species to those living today and also link two species living today Today’s species do not look very similar, but as we go lower in the fossil layers the differences disappear 3 Geographical distribution of organisms on the earth supports descent with modification If one species descended from another: there should be some geographic continuity from where the ancestor species and the descendent species are found Look who lives in America and is a marsupial? Marsupial mammals are found in the Americas as well as Australia They are not found swimming across the Pacific Ocean, nor have they been discovered wandering the Asia. How could marsupials have gotten from one place to a location half a world away? 4 Continental drift Continents have been and are constantly on the move Caused by Constant slow movement of plates of earth’s crust on the underlying molten mantel Continental drift animation Continental drift shows that continents came together 250 mya and drifted apart 180 mya Marsupials rode the continents to their present positions 5 DNA and protein sequences support descent with modification If one species descended from another we expect that similar species should have similar DNA or similar proteins 6 Structures present during embryo stages support descent with modification Since embryo development is coded in the DNA (inherited and changeable) Related species will have similar embryo development 7