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Clemson BIOL 3350 - The Evidence for Evolution
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BIOL 3350 1st Edition Lecture 2Outline of Last Lecture I. What is Evolution?II. How can evolution occur?III. What does evolution do for you?Outline of Current Lecture I. Evidence exists for change in the eartha. Geologyb. Stratigraphyc. Principle of superpositiond. Principle of cross-cutting relationshipse. Principle of faunal successionf. Cladogramsg. Radiometric Datingh. Phylogenies reconstruct evolutionary historyi. Understanding the origin of key innovationsj. Hypothesis of the evolution of feathers starting in theropodsk. Early hypotheses to explain changes in earthCurrent LectureI. Evidence exists for change in the eartha. Geologyi. Fossils are found in layersii. Azoic layers are always deeper than Zoic layers1. Azoic – without evidence of past life (w/o fossils)2. Zoic – with evidence of past lifeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Stratigraphyi. The geological history of Earth is found in its layersii. Clear layers of different color and rock composition 1. Different layers correspond to different time periods2. Paleozoic period lasted about 3 million years – explosion of diversity of multicellular organisms in the beginning, 251 million years ago there was a mass extinction (90% of marine life disappeared)3. Layer of basement rocks – hard rock life granite and schist (typically do not contain fossils)c. Principle of superpositioni. Principle of superposition - Layers that are found lower in a rock formation are older than the layers that occur higher upii. New red layer that cuts across layers is younger b/c plate tectonics and rocks move apart allowing new sediment to fill in the gapsiii. Can use this info to date fossils depending on which layer in which the fossils were found – Relative Datingd. Principle of cross-cutting relationshipsi. Principle of cross-cutting relationships – layers/veins that are cutting through old layers is made up of younger, igneous rock (rock from volcanoes)1. Hypothesis – cracks in layers, volcanic activity, and molten rock filled in crackse. Principle of faunal successioni. Principle of faunal succession – the lower level fossils represent an earlier stage in evolution for group that shows relation also in higher levels, the higher levels are more recent and evolvedii. Ex. – Trilobites, the ones in the lower Cambrian level are older and more primitive than the ones in the Permian Periodf. Cladogramsi. Location of fossils allows reconstruction of phylogeny and time since divergence from common ancestorsii. Look how certain traits may have changed through time, from organism inlower layer to related organism in higher leveliii. Guanlong – fossil found by scientists that was dated to 160 million years ago, 9 feet long fossil of T. rex, had number of traits found only in T. rex but lacked some traitsiv. Had 3 fingers on its hand in stead of 2 (like the later ones) à use of handsbecame less later on, 2 fingers was a more advance traits that evolved later than the primitive 3 finger traitv. After time, larger body sized became more important and increased in evolutionary timeg. Radiometric datingi. Indicates that the earth is 4.5-4.6 billion years oldii. Radiometric dating (absolute dating method) uses the idea that some elements on earth are not stable, but they are radioactive and lose neutrons (to become a different element)iii. Look at rate of change over time at proportions of radioactive elements atdifferent times to see how much time has passediv. Overtime, the parent isotope decays into another element (daughter element) until eventually none of the original unstable element is leftv. Typically scientists measure how long it takes until only half of the parent isotope is left = “half-life”vi. By knowing the half-life of the element, the age of the rock can be estimatedh. Phylogenies reconstruct evolutionary historyi. Evidence exists that allows us to reconstruction evolutionary history of a groupii. Scientists use cladogram to show relationships among groups of related speciesiii. This is a hypothesis of how traits change and how species are related through timeiv. The further down on the cladogram, the more ancient the traits are; the closer to the top, the more recently evolved the speciesv. Living species are located at the terminal nodes (at the top)vi. The pattern of branching reflects the relationships between different speciesi. Understanding the origin of key innovationsi. 1970s a professor at Harvard noticed similarities between some dinosaurs(theropods) and birds à made hypotheses that birds were related to dinosaurs more than snakes and lizardsii. Think layer of filaments on its back and tail found in the Sinosauropteryx fossil àhad more than just scales; maybe they were closely related to birds and were showing primitive kinds of feathersiii. Now we have evidence of thousands of different kinds of theropods that had “proto-feathers” or primitive kinds of feathersj. Hypothesis of the evolution of feathers starting in the theropodsi. Single, unbranched, little filaments (like “A”) were the beginning ii. Now feathers are asymmetric to allow for more aerodynamic feathers in modern day birds à the living group is called “Crown-group birds” b/c it it at the top of the cladogramiii. Dinosaurs and birds shared wishbonesiv. Feathers extended across body and into dense plumage leading to modern day birdsv. Most dinosaurs couldn’t use feathers too fly b/c arms too short and bodies too heavy vi. Evolution of running up hills and flapping wings lead to longer arms/wings(hypothesis)k. Early hypotheses to explain changes on the Earthi. Catastrophism – Cuvier 1769-18321. Series of floods and sedimentation formed different layers2. Each successive fossil layer shows separate creations by God3. These catastrophes have not been observed in historic timesii. Uniformitarianism – Hutton and Lyell1. Geological processes now are the same as in the pasta. They are gradual, not catastrophes2. Implies that earth is very old and these processes are still happening


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Clemson BIOL 3350 - The Evidence for Evolution

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