1 / 33

Chapter 20 : Life’s Origin & Early Evolution

Chapter 20 : Life’s Origin & Early Evolution. Looking for Life in All the Odd Places. Fig. 20-1a, p.318. Fig. 20-1b, p.318. Looking for Life in All the Odd Places. Fig. 20-2, p.319. The Big Bang. Fig. 20-3, p.320. The Big Bang Theory.

ttibbetts
Download Presentation

Chapter 20 : Life’s Origin & Early Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 20: Life’s Origin & Early Evolution

  2. Looking for Life in All the Odd Places Fig. 20-1a, p.318

  3. Fig. 20-1b, p.318

  4. Looking for Life in All the Odd Places Fig. 20-2, p.319

  5. The Big Bang Fig. 20-3, p.320

  6. The Big Bang Theory • 12-15 billion years ago all matter was compressed into a space the size of our sun • Sudden instantaneous distribution of matter and energy throughout the known universe

  7. Archeon Eon and Earlier • 4,600 mya: Origin of Earth • 4,600 - 3,800 mya • Formation of Earth’s crust, atmosphere • Chemical and molecular evolution • First cells (anaerobic bacteria)

  8. Earth Forms • About 4.6 and 4.5 billion years ago • Minerals and ice orbiting the sun started clumping together • Heavy metals moved to Earth’s interior, lighter ones floated to surface • Produced outer crust and inner mantle

  9. Earth Is “Just Right” for Life • Smaller in diameter, gravity would not be great enough to hold onto atmosphere • Closer to sun, water would have evaporated • Farther from sun, water would have been locked up as ice

  10. First Atmosphere • Hydrogen gas • Nitrogen • Carbon monoxide • Carbon dioxide • No gaseous oxygen

  11. First Atmosphere Fig. 20-4a, p.321

  12. First Atmosphere Fig. 20-4b, p.321

  13. Origin of Organic Compounds • Amino acids, other organic compounds can form spontaneously under conditions like those on early Earth • Compounds may have formed due to events like lightning, volcanoes, asteroid impacts

  14. Chemical Evolution chlorophyll a • Spontaneous formation of porphyrin rings from formaldehyde • Components of chlorophylls and cytochromes formaldehyde porphyrin ring system Fig. 20-5, p. 322

  15. RNA World • RNA may have been first genetic material • RNA can assemble spontaneously • DNA is genetic material now • DNA-to-RNA-to-protein system is complicated • How switch from RNA to DNA might have occurred is not known

  16. Proto-Cells • Microscopic spheres of proteins or lipids can self assemble • Tiny sacs like cell membranes can form under laboratory conditions that simulate conditions in evaporating tidepools

  17. Proto-Cells Fig. 20-6b, p.322

  18. Proto-Cells Fig. 20-6c, p.322

  19. Stepped Art living cells membrane-bound proto-cells self-replicating system enclosed in a selectively permeable, protective lipid sphere enzymes and other proteins DNA RNA formation of protein-RNA systems, evolution of DNA formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions Fig. 20-7c, p.323

  20. Cambrian: Explosion of Life • Origin of photosynthetic Eubacteria • Noncyclic pathway first • Cyclic pathway next • Oxygen accumulates in atmosphere • Origin of aerobic respiration

  21. The First Cells • Originated in Archeon Eon • Were prokaryotic heterotrophs • Secured energy through anaerobic pathways • No oxygen present • Relied on glycolysis and fermentation

  22. Prokaryotes Fig. 20-8a, p.324

  23. Prokaryotes Fig. 20-8c, p.324

  24. Prokaryotes Fig. 20-7, p.324

  25. Eukaryotes • The rise of Eukaryotes was thought to have stemmed from prokaryotes

  26. Eukaryotes Fig. 20-9a, p.325

  27. Eukaryotes Fig. 20-9b, p.325

  28. Advantages of Organelles • Nuclear envelope may have helped to protect genes from competition with foreign DNA • ER channels may have protected vital proteins DNA infolding of plasma membrane Fig. 20-10, p. 326

  29. DNA infolding of plasma membrane Fig. 20-10a, p.326

  30. Theory of Endosymbiosis • Mitochondria and chloroplasts are the descendents of free-living prokaryotic organisms • Prokaryotes were engulfed by early eukaryotes and became permanent internal symbionts • Chloroplasts and Mitochondria have their own DNA

  31. Theory of Endosymbiosis photosynthetic organelle that resembles a cyanobacterium mitochondrion nucleus Fig. 20-11b, p.327

  32. hydrogen-rich anaerobic atmosphere atmospheric oxygen, 10% archaean lineage d ancestors of eukaryotes h endomembrane system and nucleus noncyclic pathway of photosynthesis f cyclic pathway of photosynthesis e b origin of prokaryotes a gaerobic respiration 3.8 billion years ago 3.2 billion years ago 2.5 billion years ago Fig. 20-12a, p.328

  33. atmospheric oxygen, 20%; the ozone layer slowly develops korigin of animals j origin of eukaryotes, the first protists korigin of fungi i endosymbiotic origin of mitochondira korigin of lineage leading to plants j endosymbiotic origin of chloroplasts Aerobic species becomes endosymbiot of anaerobic forerunner of eukaryotes. 1.2 billion years ago 900 million years ago 435 million years ago Fig. 20-12b, p.328

More Related