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Lecture 15

Lecture 15 - Mass Extinctions

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Earth Sciences

GlG105 – Lecture 15 - November 14 Set-up the drop box on blackboard for Friday November 18 th Mass Extinctions 1: Evolution and Species Images of present day starfish, and a fossil of a starfish that is 400 million yrs old – starfish didn’t change much during that time But not true for most of the animals and plants that we find today on this planet Why are we talking about mass extinctions? We wanna know how life and humans have evolved Does evolution have a mind/purpose? Or was it just chance? Why did suddenly many plants and animals on land and in oceans die off? Are humans mechanisms for mass extinction at the present time? What does the future hold? 1. Famous players/ beginnings of palaeontology Nicolaus Steno – glossopetrae are shark teeth Prodromus – relates some research he did on sharks (dissected a shark) – recognized that some fossils that were found called glossopetrae are actually shark teeth At the time were thought of as snake tongues First testable hypothesis on fossil formation – Robert Hooke – invented compound microscope, similarity of modern and petrified (fossilized) wood Suggested that new life forms had come into being through geological time Many fossil life forms no longer exist Georges Cuvier – compared mammoth jaws to Indian and African elephants– showed distinct species – documented other examples of extinct species Studied sediments of the Paris basin – rare odd mammals at base of succession – different types of fossils have been found – lower = rare odd mammals, higher layers = extinct species of elephant, top layes = present mammals Catastrophic view – succession of epochs of life, each epoch ended with a great flood – most recent = Noah’s flood He was first to recognize mass extinctions – refused to accept evolution (extinct life forms = failures of God’s plan) Jean-Baptiste Lamarck – evolution of species into new life forms - principle of faunal succession – rocks depositied at a specific time contain distinct fossils – each layer contains distinctive set of fossils William Smith – also worked out faunal succession – zone = span of rock layers containing a fossil species – range = span of time in which the species lived *Species appear and disappear – and there are times when mass extinctions occur and you have a lot of species disappearing Geological time Scale – fossil ranges used to establish relative ages – several divisions are based on mass extinctions – period names given by localities or positions – Timescale for entire Phanerozoic layer (“visible life”) 2. Evidence for Evolution a) Homologous structures (eg. Forelimbs of vertebrates) b) vestigal structures – organs that are n
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