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Change Through Time

Change Through Time. 14-1. Concepts and Principles of Evolution and Classification. The History of Life The Theory of Evolution Primate Evolution Organizing Life’s Diversity. Evolution is change.

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Change Through Time

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  1. Change ThroughTime 14-1

  2. Concepts and Principles of Evolution and Classification • The History of Life • The Theory of Evolution • Primate Evolution • Organizing Life’s Diversity

  3. Evolution is change • One of the characteristics of living things is adaptation over time to changes in their environments. • Observe the birds on page 374 – How are they adapted to their environment? • As the environment changes, populations of organisms adapt, migrate, or become extinct.

  4. Chapter 14 – History of Life • How did life begin on earth? • How are fossils used to reconstruct the history of life on earth?

  5. Early History of Earth • Early earth (4.6 billion years ago) was probably very hot. • Volcanoes erupted. • Gases helped form the atmosphere (water vapor, carbon dioxide, nitrogen, very little free oxygen)

  6. About 3.9 billion years ago… • The earth cooled, rains began, water filled the oceans. • The first living organisms are thought to have emerged between 3.9 and 3.5 billion years ago.

  7. Fossils • A fossil is evidence of an organism that lived a long time ago. • Paleontologists are scientists who study ancient life. They learn a lot from fossils: • What were organisms like? • What was the environment like?

  8. How do fossils form? • Most fossils are found in sedimentary rocks. Click here to see how. • Check out the types of fossils on page 378 of your textbook.

  9. How old is my fossil? • Scientists determine the age of fossils by: • Relative dating – fossils in top layers of rock are more recent than fossils in deeper layers (this is a geological law) • Radiometric dating – more specific age can be determined by measuring radioactive isotopes in rocks and fossils

  10. Radiometric Dating • Radioactive isotopes are atoms with unstable nuclei that decay over time and give off radiation. Carbon-14 → Nitrogen-14 • The decay rate of a radioactive isotope is called its half-life (how long it takes for half of the isotope to decay)

  11. Half-lives of some isotopes (click here to learn more about Carbon-14 dating)

  12. Geological Time Scale • Chronology of earth’s history based on fossil evidence. • History of earth is divided into 4 major eras: • Precambrian • Paleozoic • Mesozoic • Cenozoic

  13. Precambrian • 87% of earth’s history • Oldest fossils are: • 3.5 billion years old • Resemble modern photosynthetic bacteria • Prokaryotes • 1.8 billion years ago • eukaryotes evolved, • then multicellular eukaryotes like sponges and jellyfish

  14. Paleozoic • 544-245 million years ago • “Explosion” of life in the oceans • Worms, arthropods • Fish • Ferns and seed plants • Amphibians – on land! • Reptiles • Then, mass extinction wiped out 90% of ocean species and 70% of land species!

  15. Mesozoic • 245 million years ago • Continents move apart • Mammals (small) • Dinosaurs • Birds • Flowering plants • Then another mass extinction kills dinosaurs and 2/3 of all living species! (meteorite?)

  16. Cenozoic • 66 million years ago – present • Primates appeared • Modern human species appeared about 200,000 years ago

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