1 Review Why are fossils important evidence for evolution Interpret Visuals use the figure on pg 394-395 to describe how a modern mystcete whale is different from Ambulocetus 2 Explain what is the relationship between Hox genes and embryological development Draw Conclusions Organisms A and B have very similar Hox genes, and their embryos, in early development, are also very similar. What do these similarities indicate about the ancestry of organisms A and B 3 Explanation In your own words, write a paragraph that explains how evidence since Darwin’s time has strengthened his theories. CH 16 DARWIN’S THEORY OF EVOLUTION 16.4 Evidence of Evolution The fields of geology, physics, paleontology, chemistry, and embryology, did not have the technology or understanding to test Darwin’s assumptions during his lifetime Genetics and molecular biology didn’t exist. In the 150 years since Darwin published On the Origin of Species, discoveries in all these fields have served as independent tests that have supported Darwin’s ideas about evolution. Biogeography Study of where organisms live now and where they and their ancestors lived in the past. Closely Related but Different Biogeography of Galapagos species suggested that populations on the island had evolved from mainland species Natural selection on the islands produced variations among populations that resulted in different, but closely related, island species. Distantly Related but Similar Rhea, Ostriches, and Emus Differences in body structures provide evidence that they evolved from different ancestors Similarities provide evidence that similar selection pressures had caused distantly-related species to develop similar adaptations. The Age of Earth and Fossils Fossils form series that trace the evolution of modern species from extinct ancestors. The Age of Earth Evolution takes a long time Hutton and Lyell argued that Earth was indeed very old, but couldn’t determine just how old Geologists use radioactivity to establish the age of certain rocks and fossils which indicates the Earth is about 4.5 billion years. Recent Fossil Finds Since 1859 MANY more fossils have been found Page 394-395. Limb structure suggests that these animals could both swim in shallow water and walk on land. The hind limbs were short and probably not able to bear much weight Spent most of their time in water. Streamlined body and reduced hind limb. suggest it spent its entire life swimming in the ocean. Retain reduced pelvic bones and some even upper and lower limb bones No longer play a role in locomotion. Comparing Anatomy and Embryology Homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. Homologous Structures Similar structures that may serve different functions in various organisms. Analogous Structures Body parts that share a common function, but not structure Wing of a bee and a wing of a bird. Vestigial Structures Inherited from ancestors, but have lost much or all of their original function due to different selection pressures Hipbones of bottlenose dolphins Wings of flightless cormorant . Embryology Early developmental stages of many vertebrates look very similar Same groups of embryonic cells develop in the same order and in similar patterns to produce many homologous tissues and organs in vertebrates. Life’s Common Genetic Code All living cells use information coded in DNA and RNA to carry information from one generation to the next and to direct protein synthesis. Homologous Molecules Many different organisms share homologous proteins Hox gene. Testing Natural Selection Grants tested the Galapagos finches. Two Testable Assumptions 1. 2. There must be enough heritable variation in beak size and shape to provide raw material for natural selection Differences in beak size and shape must produce differences in fitness. Used medium ground finch on the island of Daphne Major Supports good-sized finch populations Allows them to catch, tag, and identify nearly every bird of the species. Periodically recapture the birds Record which individuals are alive and which have died, which have reproduced and which have not Record anatomical characteristics like wing length, leg length, beak length, beak depth, beak color, feather color, and total mass of each bird. When food becomes scarce during dry periods, birds with the largest beaks are more likely to survive. The Grants have documented that natural selection takes place in wild finch populations frequently, and sometimes rapidly Without heritable variation in beak sizes, the medium ground finch would not be able to adapt to feeding on larger, tougher seeds during a drought. Like any scientific theory, evolutionary theory is constantly reviewed as new data are gathered There is significant uncertainty about exactly how life began Questions that remain are about how evolution works - not whether evolution occurs. Competition and environmental change drive natural selection Traits that don’t matter much under one set of environmental conditions became adaptive as the environment changes during a drought.