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History of Life

History of Life. Chapter 19. The Fossil Record 19.1. Any evidence of an organism that lived long ago and are now extinct Most are formed in sedimentary rocks Provides info about structure, environment and way of life. Types of Fossils. Imprint. Cast. Mold. Trace. Amber-preserved.

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History of Life

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  1. History of Life Chapter 19

  2. The Fossil Record 19.1 • Any evidence of an organism that lived long ago and are now extinct • Most are formed in sedimentary rocks • Provides info about structure, environment and way of life

  3. Types of Fossils Imprint Cast Mold Trace Amber-preserved

  4. How are fossils formed?

  5. Dating Earth’s History

  6. Relative Dating • Uses the position of fossils in sediment layers • Oldest at the bottom layer, youngest on top, not actual age • Index fossil • an easily recognized and widespread fossil used to compare the relative ages of rocks, ex. trilobites

  7. Radiometric Dating • Uses radioactive isotopes (atoms with unstable nuclei that break down or decay) • Half-life – the time required for half of the radioactive atoms in a sample to decay • Potassium 40, half-life = 1.3 billion years • Carbon 14, half-life = 5730 years

  8. Geologic Time Scale

  9. Geological Time Scale • Based on both relative and absolute dating • Major divisions • Eons • Eras • Periods

  10. Precambrian Era • Starts 4.7 bya • Life began • Accounts for 90 % of Earth’s history • Primitive prokaryote were the first forms of life

  11. Paleozoic Era • Appearance of plants and animals including fishes, reptiles, amphibians and ferns • Mesozoic Era • Mammals and dinosaurs • Flowering plants • Cenozoic Era • Primates • Modern human (200,000 years ago)

  12. Life on a changing planet • Physical forces • Geological forces (building mountains and moving whole continents) have altered habitats of living organisms throughout Earth’s history • Plate tectonic theory • Explains the movement of continents (3 cm/year) • Africa and South America separated by Atlantic Ocean

  13. Biological forces • Actions of living organism have changed conditions in the land, water, and atmosphere of the Earth • Earth cooled as CO2 decreased; used by early photosynthetic organisms

  14. Patterns and Processes of Evolution 19.2

  15. What processes influence survival or extinction of species and clades? • Clades • Group of species that includes a common ancestor and all descendants of that ancestor, living or extinct.

  16. The more varied the species (more diversity) in a particular clade are, the more likely the clade is to survive environmental change.

  17. Patterns of Extinction • Background extinction • Slow steady process of natural selection • Mass extinction • An event during which many types of living things suddenly die out • Makes new habitats and resources available to organisms left after a major catastrophe

  18. Rate of Evolution

  19. Gradualism • Species originate through a slow and steady change of adaptations

  20. Punctuated Equilibrium • Speciation experience long, stable periods interrupted by brief periods of rapid evolutionary change

  21. Patterns of Macroevolution

  22. Adaptive radiation • When a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways.

  23. Hawaiian honeycreepers

  24. Convergent Evolution • Distantly related organisms evolve similar traits • Unrelated species occupy similar environments in different parts of the world

  25. Coevolution • Process by which two species evolve in response to changes in each other over time • Ex. Flowers and pollinators (birds, bees, etc.)

  26. Earth’s Early History 19.3 • About 4.5 billion years old • Formed from cosmic debris colliding • Earth cooled enough for solid rocks to form and water vapor to condense and fall as rain, produce oceans • Earth’s atmosphere was primarily composed of • Carbon dioxide, water vapor, nitrogen

  27. Hypotheses on how life began

  28. Stanley Miller and Harold Urey’s experiment • Produced 21 amino acids—building blocks of proteins. • Proved incorrect • Nonlife to life is a big leap!

  29. Microspheres • Proteinoid microspheres • Contain selective permeable membrane • Water passes through • Store and release energy • About 3.8 billion years ago

  30. RNA and DNA • Hypothesized that RNA formed before DNA

  31. Origin of eukaryotic cells

  32. Endosymbiotic theory • Prokaryotes were the ancestors of eukaryotic organisms • Small prokaryotes began living inside the larger cells

  33. Mitochodria • evolved from endosymbiotic prokaryotes that are able to use oxygen to generate energy-rich ATP • Chloroplasts • Evolved from endosymbiotic prokaryotes had the ability to photosynthesize

  34. Modern evidence • Lynn Margulis (1960) • Supported endosymbiotic theory • Mitochondria and chloroplasts have DNA similar to bacterial DNA • Both have ribosomes resembling those of bacteria • Reproduce by binary fission when cells containing them divide by mitosis

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