CHAPTER 14: EARTH’S HISTORY Earth’s History • Earth’s history is long and fascinating. • There have been great biological and geological changes Fossil Records • The fossil record provides strong evidence of the evolution of life Triceratops Nicholas Steno • Earth’s history has been unveiled by scientists applying the tools of critical thinking • Nicholas Steno was a Danish theologian • First to suggest that fossils had once been living organisms • Developed the Principles of Original Horizontality, Superposition, and Lateral Continuity James Hutton • Scottish naturalist and physician • Father of geologic time • Proposed that geologic time was indefinitely long • Believed the Earth was self-renewing (basis of rock cycle) • Formulated the principle of uniformitarianism Charles Lyell • • • • • British lawyer Father of Modern Geology Wrote Principles of Geology Popularized Principle of Uniformitarianism Developed the Principles of Cross-cutting Relationships and Inclusions Charles Darwin • English naturalist and geologist • Studied Lyell’s Principles of Geology • Wrote On the Origin of Species by Means of Natural Selection • Credited with the Theory of Evolution Natural Selection • All living things develop over time from a very few simple forms All individuals survive equally Conditions change and only welladapted individuals survive New generation is dominated by welladapted individuals Can you think of a change in conditions that might lead to natural selection? Fossils • Fossils are the remains of animals and plants, or traces of their presence, that have been preserved in the crust. • Fossils preserve a record of past life. How Are Fossils Made? • Fossilization is the process that turns a once-living thing into a fossil. • The Fossil record is biased. Rapid burial is required. In most cases just shell, teeth, and bones are preserved. • Preservation is typically by: replacement or formation of a mold or cast. Brachiopod shells Rare, soft part preservation (dinosaur skin) Are these molds or casts or both? Is there evidence of replacement here? There are several lines of evidence for evolution • Phylogeny Phylogeny is the history of organismal lineages as they change through time. What are some of the changes evident in the phylogeny of the horse? Homologous Structures Vestigial Structures How does the existence of vestigial structures support the concept of evolution? Embryology • Even distantly related organisms have similar embryonic forms that can be traced back to their evolutionary history Molecular biology also provides evidence of evolution • Changes within separate populations of the same species result in new species through natural selection. • Genetic Mutation – (random changes to RNA or DNA) • Genetic Variation – (differences in inherited traits) Molecular biology documents the relationship of living organisms to their ancestors Parasitic microbes, viruses, bacteria ... all evolve! Extinctions • Mass extinctions are dramatic events in the otherwise slow process of evolution Which of the Phanerozoic extinctions had the greatest impact on marine organisms? Which one lead to the extinction of the terrestrial dinosaurs? Extinction • During a mass extinction large numbers of species die out within a relatively short period of time. There are various hypotheses for each mass extinction ... Geologic Time Scale • The Geologic Time Scale is the “calendar” of events in Earth’s history Geologic Column Drag and Drop Animation Hadean Eon • • • • • • • • • Heating of the interior Magma “ocean” “Iron Catastrophe” Eventual cooling Earliest crust and oceans Ended ~ 3.8 bya Began ~ 4.6 bya Extraterrestrial barrage Atmosphere rich in methane, ammonia and carbon dioxide Why was the Earth so much hotter during the Hadean than it is now? The Archean and Proterozoic Eons lasted from 3.8 million to 542 million years ago Archean and Proterozoic cratons (i.e., continent crustal blocks) Archean Eon • Atmosphere noxious to modern organisms (methane, ammonia, carbon dioxide, and water vapor) • More extraterrestrial bombardment • More volcanic outgassing • Continental Cratons form • Abundant life first appears (stromatolites) • Photosynthesis initiated The atmosphere of the Archean would have been noxious to us. What component of our atmosphere would have been noxious to the Archeans? Ancient and modern stromatolites Proterozoic Eon • • • • Continents develop, clustered together (Rodinia) in the southern hemisphere Mountain building Atmosphere becomes gradually more oxygenated Diversification of soft-bodied organisms Phanerozoic Eon • • • • • • • ~ 542 mya to present Includes the Paleozoic, Mesozoic and Cenozoic eras Major mountain-building events Pangaea continues break up into modern continents Complex life evolves with much diversification Geographic separation isolates some populations Punctuated by mass extinctions Tiktaalik roseae - a critical transitional organism from Canada’s Arctic In the Paleozoic Era complex life evolved and the continents reorganized The Cambrian Explosion • Organisms that evolved during the Cambrian Explosion, developed some of the basic inherited traits that are still present today, and others that vanished forever. Steven Earle Steven Earle Steven Earle Steven Earle What is so important about the fossils of the Burgess Shale in the Canadian Rockies? In the Mesozoic Era biological diversity increased and continents reorganized yet again Mesozoic diversity Steven Earle Plesiosaur Allosaurus claw Dicot leaf The Tethys Sea • Continents separated and moved towards their present configuration. The Tethys Sea (the ancestor to the Pacific Ocean) wrapped the globe along the equator. Tethys Sea Mammals and birds diversified and primates arose during the Cenozoic Era a b c d (a) Sahelanthropus tchadensis (b) Australopithecus afarensis (c) Homo erectus (d) Homo sapiens sapiens Earth in the Quaternary Period Why was sea level relatively low during much of the Quaternary? COPYRIGHT Copyright © 2014 John Wiley & Sons Canada, Ltd. All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful. 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