Chapter 17 The History of Life

1. Chapter 17The History of Life The Fossil Record (pp. 417-422) Earth’s Early History (pp. 423-428) Evolution of Multicellular Life (pp.429-434) Patterns of Evolution (pp. 435-440 Created by C. Ippolito July 2005

2. Chapter 17 Section 1The Fossil Record Objectives: Describe the fossil record. State the information that relative dating and radioactive dating provide about fossils Identify the divisions of the geological time scale. Created by C. Ippolito July 2005

3. Fossils and Ancient Life • Paleontologists • Scientists who collect and study fossils • Structure of organisms • What organisms ate • Who ate them • Environment lived in • Fossil Record • All information inferred by study of fossils • Evidence of the history of life on Earth • How groups of organisms changed over time Created by C. Ippolito July 2005

4. How Fossils Form • Fossils form in sedimentary rock • Rock exposed to rain, heat, wind, and cold breaks into small particles • Particles settle to the bottom in layers • Fossils form when: • Particles cover remains of dead organism • imprint left in rock after decay (imprint) • hard parts replaced by minerals (petrifaction) • complete cover before decay by fine particles (mold) • Body caught in plant resin (amber) Created by C. Ippolito July 2005

5. Types of Fossils • Mold Fossils • Imprint Fossil • Petrified Fossil • Fossil in Amber Created by C. Ippolito July 2005

6. Interpreting Fossil Evidence • Two ways to determine age of fossil: • Relative Dating – age compared to other fossils • Sedimentary rock forms in layers • Oldest in lower layers • More recent in upper layers • Index Fossils • Short lived • Found in specific layers • Radioactive Dating – age calculated based on amount radioisotopes found in sample • Half-life – time for half of radioisotope to decay • Carbon-14 ---- 5730 years • Potassium-40 ---- 1.25 billion years Created by C. Ippolito July 2005

7. Geological Time Scale • Developed to represent evolutionary time • Precambrian Time – Big Bang to first multicellular life forms (88% of time) • Eras • Paleozoic – vertebrates & invertebrate life • Mesozoic – age of dinosaurs • Cenozoic – age of mammals • Periods • Smaller subdivisions of the eras Created by C. Ippolito July 2005

8. Geological Time Scale • If we consider time scale as 24 hours: Created by C. Ippolito July 2005

9. Homework Section Assessment 17-1 on page 422 (1 thru 4) and Checkpoints on pages 418 and 420 Created by C. Ippolito July 2005

10. Chapter 17 Section 2Earth’s Early History Objectives: Describe how conditions on early Earth were different from conditions today. Explain what Miller and Urey’s experiments showed. State the hypotheses that have been proposed for how life first arose on Earth. Identify some of the main evolutionary steps in the early evolution of life. Created by C. Ippolito July 2005

11. Formation of Earth • Post Big Bang cosmic debris attracted together over 100 million years • As surface cooled molten material  crust; then oceans • Surface broken by many volcanoes • Early Atmosphere – very different gases • hydrogen cyanide (HCN) • carbon dioxide (CO2) • carbon monoxide (CO) • nitrogen (N2) • hydrogen sulfide (H2S) • water (H2O) Created by C. Ippolito July 2005

12. First Organic Molecules • Urey Miller Experiment • Lab simulation of early atmosphere • Gases • methane (CH4) • ammonia (NH3) • water (H2O) • Energy • Spark (lightning) • Heat (Bunsen burner) • Radiation (sun lamps) • Result • Water contained amino acids and simple sugars Created by C. Ippolito July 2005

13. How Did Life Begin? • Formation of Microspheres • Sidney Fox Experiment • Clusters of proteins form cell-like structures (a.k.a coacervates or proteinoids) • Some may contain “enzymes” • Evolution of DNA and RNA • Origin unknown some hypothesis include various ways of self replication Created by C. Ippolito July 2005

14. Free Oxygen • Microfossils – prokaryotic cells • Appear to be similar to modern bacteria • Anaerobic Respiration Life • Lack of free oxygen in atmosphere • Used nutrients in oceans and add carbon dioxide • Photosynthetic Life • Primitive photosynthetic bacteria • Make own food and add free oxygen • Aerobic Respiration Life • Free oxygen allows more frugal use of nutrients Created by C. Ippolito July 2005

15. Origin of Eukaryotic Cells • Endosymbiotic Theory • Proposed by Lynn Margulis • Eukaryotic cells with organelles formed from communities of prokaryotic cells • DNA in mitochondria and chloroplasts Created by C. Ippolito July 2005

16. Homework Section Assessment 17-2 on page 428 (1 thru 5) and Checkpoints on page 424 and 426 Created by C. Ippolito July 2005

17. Chapter 17 Section 3Evolution of Multicellular Life Objectives: Describe the key forms of life in the Paleozoic, Mesozoic, and Cenozoic Eras. Created by C. Ippolito July 2005

18. Precambrian Time • Longest period of Earth’s history • Prokaryotic cells • Anaerobic • Photosynthetic • Aerobic • Eukaryotic Cells • Soft Bodied Multicellular Organisms Created by C. Ippolito July 2005

19. Paleozoic Era • Rapid evolution of marine life • Cambrian Period • Invertebrates – jellyfish, worms, sponges • Shelled – clam and mussel ancestors • Exoskeleton – Trilobites • Ordovician and Silurian Periods • Invertebrates – octopi, squid, insects • Land Plants • Vertebrates – jawless fish • Devonian Period • Ferns • Fish – sharks, bony fish with scales • Land Animals - amphibians • Carboniferous and Permian Periods • Land Animals – reptiles and winged insects • FIRST MASS EXTINCTION occurs – most marine organisms die out Created by C. Ippolito July 2005

20. Mesozoic Era • Age of Dinosaurs • Flowering Plants appear • Triassic Period • First dinosaurs • Small mammals • Jurassic Period • Dinosaurs dominant • Archaeopteryx – first bird • Cretaceous • T. Rex dominant • Flowering plants • SECOND MASS EXTINCTION occurs – 50% of organisms die out – all of dinosaurs Created by C. Ippolito July 2005

21. Cenozoic Era • Age of Mammals • Tertiary Period • Grasses evolve • Large grazing mammals and birds • Quaternary Period • Multiple Ice Ages and Glacial Movements • Man appears at end Created by C. Ippolito July 2005

22. Homework Section Assessment 17-3 on page 434 (1 thru 4) and Checkpoints on pages 430 and 432 Created by C. Ippolito July 2005

23. Chapter 16 Section 4Patterns of Evolution Objectives: Identify important patterns of macroevolution. Created by C. Ippolito July 2005

24. Macroevolution • Large scale evolutionary changes that occurred over long periods of time • Mass Extinction • Permian – volcanic activity and shifting continents • Cretaceous – asteroid collision in Caribbean Ocean • Adaptive Radiation • One ancestral form changes in to many different form to take advantage of adaptations (finches) Created by C. Ippolito July 2005

25. Convergent Evolution • Natural selection causes unrelated species to resemble one another. • Analogous structures are produced by convergent evolution. bandicoot rat Created by C. Ippolito July 2005

26. Coevolution • Two or more species evolve in response to each other through cooperative or competitive adaptations Created by C. Ippolito July 2005

27. Rate of Evolution • Gradualism - species arise slowly and continuously as changes accumulate over millions of years • Punctuated Equilibrium - species stay same for long periods and change abruptly by spurts of rapid evolution Created by C. Ippolito July 2005

28. Homework Section Assessment 16-4 on page 440 (1 thru 5) and Checkpoints on pages 437 and 438 Created by C. Ippolito July 2005