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Evidence for Evolution Archaeopteryx Main lines of evidence for evolution come from: 1. Fossils 2. Embryology 3. Geographic Distribution of 4. Artificial Selection 5. Homologous Structures 6. Vestigial Structures 7. Comparative Analysis of DNA 1 Fossils: Fossils are _________________________________________________________. Scientists determine the age of fossils by : 1. Examining the ___________ above and below the fossil’s ______________. 2. Radiometric Dating is…. 3. Earth is ________________________ years old. Transitional Fossils are important because: Whale evolution example: Below are just a few of the transitional fossils between modern whales and their terrestrial (land-dwelling) ancestors. Modern Whale - ___________________________ Tail evolved into flipper Ears modified to hear underwater Basilosaurus -______________________________ Sturdy Flippers Still has small weak hind legs Ambulocetus - _________________________________ Forelimbs with fingers/small hooves Hind feet and tail adapted for swimming Mesocynids - _________________________________ Limbs adapted to moving on land Ears adapted to hearing in air Scientists combine evidence from fossil record with other lines of evidence to provide the most complete understanding of the change in organisms over time as possible. As more evidence is accumulated, this understanding is continuously modified. Sometimes this involves heated debates! 2 Embryology Activity: Organize the cards on the chart: Q 1: How did you decide which card went in which area of the chart? Q 2: Where did you struggle deciding the correct place for embryos? Why? AFTER THE TEACHER SHARES THE ANSWERS Q 3: Which organisms do you think are more related? Why? Embryology: Study of early ___________ developmental stages of organisms Early developmental stages of related animals are ____________________. More ____________ = more ____________________________________. Example: Analyzing Geographic Distribution of Organisms around the world Similar environments around the world contain organisms that are DIFFERENT species but have similar anatomies and/or behaviors because: ______________________________________________________________________________ Example: Artificial Selection: When ________________________ with a desired _____________ repeatedly until the trait becomes _____________ in the population Examples: Homologous Structures: A shared _____________________ that provides evidence that the organisms had a ______________________ with that trait. Example: 3 Vestigial Structures: A trait that was useful to an ______________ and has been ________________, but is not useful to the current __________________ Examples: Comparative Analysis of DNA: If all _______ evolved from the same ______________ (3.5 bya), then all should share some common ______________. The greater the __________________between 2 species = more recent they have a _________ Analysis Questions: Use your notes and the book (esp. pages 382-385) to answer the following questions. 1. Fill in the description of the whale trait we find in each of the transition fossils: Mesochynids Ambulocetus Basilosaurus Modern cetaceans Location of nostrils Why are transition fossils important in understanding evolution? 2. Compare and contrast artificial selection with natural selection. 3. How do homologous structures provide evidence for evolution? 4. What is a vestigial structure? Give an example of a vestigial structure and its former function in the ancestral organism. 5. Why do the early stage embryos of vertebrates look strikingly similar? 6. Would you expect the DNA of 2 species that share an ancestor 1 million years ago to be more or less similar than 2 species that share an ancestor 100 million years ago? WHY? 4