08 - Evolution Reconstruction of the fossil whale...

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1 Evolution Evolution Reconstruction of the fossil whale Ambulocetus natans from the Eocene of Pakistan (~ 49 million years ago). Ambulocetus, discovered in 1994, was the first in a series of remarkable discoveries of whale skeletons that documented the evolutionary transition from land mammals to obligate aquatic whales. What is a fossil? What is a fossil? • A fossil is the mark of ancient life preserved in the rock record • Three types of fossils – Body fossil = a fossil in the shape of all or part of an ancient organism’s body – Trace fossil = a fossil documenting an organism’s interaction with its environment – Chemical fossil = a (usually organic) molecule produced by an ancient organism Body fossil Trace fossil Chemical fossil What do we learn from What do we learn from fossils, and how? fossils, and how? • The information available from fossils depends on type • Body fossils tell us about the shape (or form) of an organism – They provide no direct information about what an organism does, but – They can be used to infer an enormous amount of information because of the relationship between form and function Form is related to function Form is related to function Janjucetus, 25 million year old whale ancestor close-up view of minke whale baleen
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2 What do we learn from What do we learn from fossils, and how? fossils, and how? • Trace fossils tell us about the activity of an animal – They provide a direct record of behavior, but – They often provide limited evidence for the shape of the animal that created them, so we don’t know which organism they represent ~200 million year old Thalassinoides , burrows produced by crustaceans What do we learn from What do we learn from fossils, and how? fossils, and how? • Chemical fossils record the earliest life on Earth, and tell us about the biochemistry of ancient organisms – The chemicals produced by organisms also serve functions , and so tell us a lot about what ancient organisms did Souza-Egipsy et al., 2006 “biomarkers” Sudden appearance of life at the Sudden appearance of life at the beginning of the Paleozoic Known Diversity Through Geologic Time 1860 Sudden appearance of life The fossil record: What types of The fossil record: What types of organisms, when? organisms, when?
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3 The fossil record: Change The fossil record: Change • One simple message from the fossil record has been evident for millennia: that the history of life is full of change Change leads to modern diversity! 505mya (Cambrian) 80 mya (Cretaceous) 0.02 mya (Pleistocene) Mezosaur- marine reptile Change = evolution Change = evolution • The central ideas of evolution are that life has a history—it has changed over time—and that different species share common ancestors . • The process of evolution produces a pattern of relationships between species.
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08 - Evolution Reconstruction of the fossil whale...

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