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The History of Life

The History of Life. Alan D. Morales, ATC/L, M.Ed. Earth’s Early History. Formation of Earth Not born in a single event Cosmic debris collided together producing heat that formed planet. Occurred over 100s of years Earth age: 4.5-4.6 mya

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The History of Life

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  1. The History of Life Alan D. Morales, ATC/L, M.Ed.

  2. Earth’s Early History • Formation of Earth • Not born in a single event • Cosmic debris collided together producing heat that formed planet. • Occurred over 100s of years • Earth age: 4.5-4.6 mya • Elements rearranged themselves according to their density

  3. Earth’s Early Atmosphere • Consisted hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, & water • 4 billion yrs ago • Earth cooled enough to allow rocks to form • Violent volcanic activity shook the Earth’s crust • Comets & Asteroids bombarded its surface • 3.8 billion yrs. Ago • Earth’s surface cooled to allow water to remain liquid • T-storms drenched the planet covering earth surface with water • Fossils indicated when 1st life form appeared

  4. Earth’s Early Atmosphere

  5. Fossil Review • Paleontologist: • scientist who study fossils & develop fossil records • Fossil record: • provides evidence about the history of life on Earth & shows how different groups of organisms have evolved. • How fossils form: • In sedimentary rock • Particles settles in bottom of seas or lakes • Layers of sediment accumulate over specimens causing it to sink, bury, & compress • Quality will vary producing imprint or preserve

  6. Fossil Review • Interpreting Fossil Evidence • Scientist reconstruct extinct species from fossil pieces and strata layers

  7. Age of Fossils • Relative Dating • Method used to determine the age of rocks by comparing them with those in other layers • Law of Superposition • states that younger layer of rock are deposited on top of older layers. • Radioactive Dating • Using the decay of radioactive isotopes to measure the age of the rock.

  8. Earth’s Strata Layers

  9. Geologic Time Scale • A record of Earth’s history • Subdivisions • Mya-million years ago • Epochs-several million years • Period-10s of millions of years • Era-100s of millions of years • Eon-billions of years

  10. Geologic Time Scale • Precambrian Time • Simple anaerobic; photosynthetic; & aerobic life form • Eurokaryic cells & multicellular organisms appeared • Palezoic Era • Cambrian • Ordovician & Silurian • Devonian • Carboniferous & Permian • Mesozoic Era • Triassic • Jurassic • Cretaceous • Cenozoic Era • Tertiary • Quaternary

  11. Era of Earth History • Precambrian Time • About 88% of Earth History • Paleozoic Era • Cambrian explosion • Evolution of fishes, land plants, insects, and reptiles • Permian extinction

  12. Era of Earth History • Mesozoic Era • Evolution of land animals • Continental drift • Plate tectonics • Cretaceous extinction • K-T Boundary-Earth’s layer with high level of iridium

  13. Continental Drift

  14. Era of Earth History • Cenozoic Era • Age of the Mammals

  15. How did life begin?

  16. Early Origins of Life • Spontaneous generation • Life arises from nonlife • Theory of Biogenesis • States that only living organisms can produce other living organisms

  17. First Organic Molecules • Miller & Urey experiment • Filled flask with hydrogen, methane, ammonia, & water which represented earth atmosphere • Passed a electric spark in environment • Produced some amino acids. • Suggested how mixtures of the organic compounds necessary for life could have arisen form simpler compound present on a primitive Earth

  18. Miller & Urey experiment

  19. Origin of Life • Formation of Microspheres • Amino Acids and clay • Similar structures might acquired more characteristics of living cells • Evolution of RNA & DNA • Suggested that RNA could have evolved before DNA. • Several steps could lead to protein synthesis and organism formation

  20. First Cells • Prokaryotic cells (cyanobacteria) • Prokaryotic cells developed process of photosynthesis • Produced free oxygen • About 2.5 bya • Changed Earth atmosphere

  21. Free Oxygen • First atmosphere had little or no oxygen • O2 combined with iron producing rust which fell to the floor changing the color to blue-green • O2 accumulated in atmosphere causing decrease in methane & hydrogen sulfide • Rise of O2 drove some life forms to extinction while others evolved

  22. Origin of Eukaryotic Cells • Endosymbiotic Theory • Proposed that eukaryotic cells arose from living communities formed by prokaryotic organisms about 1.8 bya • Supported: • Mitochondria & Chloroplast DNA, ribosomes, and reproductive methods

  23. Endosymbiotic Theory

  24. Sexual Reproduction & Multicellular Life • Eukaryotic cells developed the ability to sexual reproduce • Why important? • Speeds up evolutionary process

  25. The End

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