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The Fossil Record and Geologic Time Scale 19-1 The Fossil Record The Fossil Record and Geologic Time Scale Chapter 19.1 Essential Questions • What do fossils reveal about ancient life? • How do we date events in Earth’s history? • How was the geologic time scale established, and what are its major divisions? • How have our planet’s environment and living things affected each other to shape the history of life on Earth? The Fossil Record and Geologic Time Scale Fossils and Ancient Life – Fossil record: Provides evidence about the history of life on Earth. Shows how organisms have changed over time. – More than 99% of all species that have ever lived on Earth are extinct. Copyright Pearson Prentice Hall The Fossil Record and Geologic Time Scale • Specific conditions are needed for fossilization. • Small % of living things became fossils. • Many did not leave a trace • fossil record is incomplete. The Fossil Record and Geologic Time Scale Fossils can form in several ways. • Permineralization occurs when minerals carried by water are deposited around a hard structure. • A natural cast forms when flowing water removes all of the original tissue, leaving an impression. The Fossil Record and Geologic Time Scale • Trace fossils record the activity of an organism. The Fossil Record and Geologic Time Scale Interpreting Fossil Evidence: Relative Dating The Age of fossils can be determined by: Relative dating and/or Radiometric dating Relative dating: Compare the placement of fossils in layers of rock Index fossils! The Fossil Record and Geologic Time Scale • Radiometric dating uses decay of unstable isotopes. – Isotopes are atoms of an element that differ in their number of neutrons. – Radioactive isotopes decay into stable isotopes at a rate that can be measured. neutrons protrons The Fossil Record and Geologic Time Scale • Radiometric Dating – A half-life (t1/2) is the amount of time it takes for half of the isotope to decay. The Fossil Record and Geologic Time Scale Copyright Pearson Prentice Hall The Fossil Record and Geologic Time Scale The Fossil Record and Geologic Time Scale Evidence of Continental Drift The Fossil Record and Geologic Time Scale 19-2 Patterns and Processes of Evolution The Fossil Record and Geologic Time Scale Chapter 19.2 Essential Questions • What processes influence whether species and clades survive or become extinct? • How fast does evolution take place? • What are 2 patterns of macroevolution? • What evolutionary characteristics are typical of coevolving species? The Fossil Record and Geologic Time Scale Speciation and Extinction Macroevolution refers to largescale evolutionary patterns and processes that occur over long periods of time. The Fossil Record and Geologic Time Scale Macroevolution Six important topics in macroevolution are: 1. Extinction 2. Adaptive radiation 3. Convergent evolution 4. Coevolution 5. Punctuated equilibrium 6. Changes in developmental genes (Hox Genes) The Fossil Record and Geologic Time Scale Extinction • Background extinction: Slow and steady extinction • Mass extinction: Drastic change causes many species to become extinct in a short period of time. The Fossil Record and Geologic Time Scale Extinction • What effects have mass extinctions had on the history of life? • Mass extinctions have: – Provided ecological opportunities for organisms that survive – Resulted in bursts of evolution that produced many new species The Fossil Record and Geologic Time Scale The Fossil Record and Geologic Time Scale Gradualism • Darwin felt that evolution was slow and steady The Fossil Record and Geologic Time Scale Punctuated Equilibrium: The Fossil Record and Geologic Time Scale Reasons for rapid evolution • Small population – becomes isolated – migrates to a new environment • Mass extinctions allow species to fill their niche The Fossil Record and Geologic Time Scale The Fossil Record and Geologic Time Scale Macroevolution : Adaptive Radiation • Adaptive radiation: • Process by which a small group of species evolves into several different forms. The Fossil Record and Geologic Time Scale Adaptive Radiation • Two species can’t occupy the same niche within an ecosystem – i.e. can’t have large mammal carnivores and large reptile carnivores…one is going to prevail • If there is an opening within a system, due to extinction, then another species will fill that niche – i.e. dinosaurs became extinct, so mammals filled the niches left open The Fossil Record and Geologic Time Scale Macroevolution: • Convergent evolution: The process by which distantly related organisms come to resemble one another, which results in analogous structures. The Fossil Record and Geologic Time Scale • Sometimes organisms that are closely connected to one another by ecological interactions evolve together. • Coevolution: Process by which 2 species evolve in response to changes in each other over time. The Fossil Record and Geologic Time Scale 19-3 Earth’s Early History The Fossil Record and Geologic Time Scale Chapter 19.3 Essential Questions • What do scientists hypothesize about early Earth and the origin of life? • What theory explains the origin of eukaryotic cells? • What is the evolutionary significance of sexual reproduction? The Fossil Record and Geologic Time Scale The Mysteries of Life’s Origin Formation of Earth • Cosmic debris collided • Meteor strikes caused it to melt • Earth cooled 4.2 BYA • Elements rearranged themselves according to density – Most dense-core – Moderately dense – crust – Least dense - atmosphere The Fossil Record and Geologic Time Scale Miller-Urey Experiment Attempted to demonstrate whether or not organic molecules could have been produced before life was present. After a week produced sugars and 21 amino acids! The Fossil Record and Geologic Time Scale Formation of Microspheres • Protenoid microspheres: bubbles given off from organic molecules – have many characteristics of living cells Semi-permeable membrane, Able to store and release energy • First forms of life were prokaryotic cells – Over time they became more and more advanced (3.8 BYA) The Fossil Record and Geologic Time Scale Evolution of RNA and DNA • RNA world hypothesis: RNA existed before DNA. • Small sequences of RNA formed from simpler molecules. The Fossil Record and Geologic Time Scale The Heterotroph Hypothesis The 1st organisms on the Earth were: • Anaerobic Heterotrophs • First prokaryotes • Simple archaen bacterial cells • Photosynthetic prokaryotes • aerobic prokaryotes, eukaryotes, multicellular organisms The Fossil Record and Geologic Time Scale Comparing Atmospheres Many scientists think Earth’s early atmosphere may have been similar to the gases released by a volcano today. The Fossil Record and Geologic Time Scale Origin of Eukaryotic Cells Endosymbiotic Theory: Eukaryotic cell organelles arose from prokaryotic organisms Specific Evidence • Mitochondria and chloroplasts: – DNA similar to bacterial DNA – Similar ribosomes – Reproduce by binary fission The Fossil Record and Geologic Time Scale Endosymbiotic Theory The Fossil Record and Geologic Time Scale Sexual Reproduction and Multicellularity • Once eukaryotic cells arose they reproduced sexually – increasing genetic variation and speeding up evolutionary change. • Multicellular organisms arose – a few hundred million years after the evolution of sexual reproduction.