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The Origins and Evolution of Life on Earth: From the Cambrian Explosion to Modern Evidence

This overview explores the origins of life on Earth, focusing on key events such as the Cambrian Explosion and the K-T Boundary. It discusses the earliest organisms and conditions that led to life, including the endosymbiont theory and fossil formation methods. Additionally, it outlines dating techniques like relative and radiometric dating, and the geological time scale, highlighting the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. The document also addresses the evolution of cellular life and the evidence supporting the theory of evolution.

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The Origins and Evolution of Life on Earth: From the Cambrian Explosion to Modern Evidence

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Presentation Transcript

  1. Page 1

  2. EQ’s 1-4 • What happened at the Cambrian Explosion? • What happened at the K-T Boundary? • What were the first type of organisms on Earth? • What does the endosymbiont theory?

  3. Page 1 Land Conditions: Earth was molten lava to start. Gravity started pulling elements together. Crust started to form

  4. Page 1 Atmosphere conditions: Probably were gases expelled from volcanoes (water, CO2, sulfur dioxide)

  5. Page 1 MODERN EVIDENCE OF EARLY LIFE Fossils- Any preserved evidence of an organism by mineral replacement, molds/casts, ice mummies or amber.

  6. Page 1 How does a fossil form? Organism must die and be covered in sediment quickly (near moving water).

  7. Page 1 On what parts of the Earth do we find fossils? Areas that were moving, shallow water when those organisms lived.

  8. Inside of cover Steps to Fossils • Organism dies near/in water • Quickly covered in sediments

  9. Inside of cover • Flesh decays, more sediments • Minerals harden in the bones

  10. Inside of cover 5. Bones decay, only minerals are left

  11. Page 2 HOW OLD ARE THESE FOSSILS? Relative Dating- Method used to determine the age of rocks by comparing them with other layers.

  12. Page 2 Radiometric dating- Uses the decay of radioactive isotopes to measure the age of a rock.

  13. Page 2 Half-life- the known amount of time it takes for half of the original isotope to decay (Uranium238 to Lead 206)

  14. Page 3 How is the time scale organized? It expresses the major geological and biological events in Earth’s history.

  15. Page 3 Eon- Time is split into PreCambrian and Phanerozoic.

  16. Page 3 Era- The next largest division (Dinosaurs=Mesozoic) Period- the divisions of an era.

  17. Page 3 Precambrian Era- The first 4 billion years on Earth, prokaryotes 1st then multicellular eukaryotes.

  18. Page 3 Paleozoic Era- Major diversification of body plans and # of species. Life in oceans 1st, then moved to land. 2 mass extinctions.

  19. Page 3 Mesozoic Era- Early mammals 1st, then dominated by reptiles (dinosaurs). 1st flowering plants and birds.

  20. Page 3 Cenozoic Era- Mammals are dominant life-form, diversified quickly

  21. Page 3 Cambrian Explosion- When ancestors of most animal groups diversified.

  22. Page 3 K-T Boundary- Layer between Mesozoic and Cenozoic eras. Evidence of impact event (iridium).

  23. Page 3 Plate Tectonics- Movement of large continental plates.

  24. Page 4 Origins of Earth Spontaneous Generation- Idea that life arises from non-life. Example- mice came from damp hay and corn

  25. Page 4 Theory of Biogenesis- Only living organisms can produce other living organisms.

  26. Page 4 How did complex molecules join together? Primordial Soup Hypothesis- If early Earth had mix of gases, organic cmpds could be made by reactions in the oceans.

  27. Page 4 Deep-Sea Vents- Some believe that these reactions began here, where sulfur forms the base of the food chain.

  28. Page 4 Order of Organic Molecule Organization 1. The first organic molecules originated

  29. Page 4 • Formation of proteins • Genetic code that could produce these proteins.

  30. Page 4 4. Formation of membranes, molecules become cells

  31. Page 4 Cellular Evolution 1. 1st cells were prokaryotes (bacteria), very simple with no nucleus or cell parts. Similar to archaea bacteria (thermophiles)

  32. Page 4 2. Photosynthesizing Prokaryotes- Archaea used sulfur for food, next organisms used light (photosynthesis)

  33. Page 4 3. Endosymbiont Theory- Ancestors of eukaryotes lived in association with prokaryotes. Explains DNA in chloroplasts and mitochondria.

  34. Page 5 Evolution- Idea that organisms CHANGE OVER TIME as a result of “genetic variations” enabling them to ADAPT to changing environments.

  35. Page 5 Evolution explains….. • How living things develop from ancestors

  36. Page 5 b. How Earth came to be populated by species

  37. Page 5 Evidence for evolution can be seen in…. • Cell similarities in all life • Similar proteins in all cells

  38. Page 5 • Many species disappearing from Earth • Living species being different from ancestors

  39. Page 5 • Organisms being suited to environments

  40. Page 5 • Extinction- When a species that once lived on the Earth no longer exists. Death rate is higher than birth rate

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