1 / 44

Origin of Life on Earth Characteristics of Early Life Self-Replication

Origin of Life on Earth Characteristics of Early Life Self-Replication Proteins aren’t self-replicating RNA may carry out catalytic functions Ribozyme – Autocatalytic RNA RNA may have been first informational molecule DNA more stable; may have arisen from RNA Nutrition

peyton
Download Presentation

Origin of Life on Earth Characteristics of Early Life Self-Replication

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. Origin of Life on Earth • Characteristics of Early Life • Self-Replication • Proteins aren’t self-replicating • RNA may carry out catalytic functions • Ribozyme – Autocatalytic RNA • RNA may have been first informational molecule • DNA more stable; may have arisen from RNA • Nutrition • First cells likely heterotrophic • No free oxygen in atmosphere of early earth • First heterotrophs probably used anaerobic fermentation (less efficient than aerobic metabolism) • First autotrophs may have used hydrogen sulfide (H2S) as hydrogen source (modern purple & green sulfur bacteria still get H from H2S) • First autotrophs to split water for H probably ancestors of modern cyanobacteria (3.1 – 3.5 bya) • Production of O2 had profound effects

  2. Origin of Life on Earth • Characteristics of Early Life • Aerobes • O2 abundant by 2.5 bya • Replaced obligate anaerobes in most areas • Aerobic metabolism much more efficient than anaerobic metabolism • Stabilized concentrations of O2 and CO2 in atmosphere • Development of ozone (O3) layer • Eukaryotes • Appeared ~2.1-2.2 bya • How might eukaryotes have arisen from prokaryotes? • Organelles (mitochondria, chloroplasts) may have originated from symbiotic relationships between prokaryote species • Chloroplasts closely related to cyanobacteria • Mitochondria closely related to alpha proteobacteria • Serial endosymbiosis

  3. Fig. 25.8

  4. Origin of Life on Earth • Characteristics of Early Life • Aerobes • O2 abundant by 2.5 bya • Replaced obligate anaerobes in most areas • Aerobic metabolism much more efficient than anaerobic metabolism • Stabilized concentrations of O2 and CO2 in atmosphere • Development of ozone (O3) layer • Eukaryotes • Appeared ~2.1-2.2 bya • How might eukaryotes have arisen from prokaryotes? • Organelles (mitochondria, chloroplasts) may have originated from symbiotic relationships between prokaryote species • Chloroplasts closely related to cyanobacteria • Mitochondria closely related to alpha proteobacteria • Serial endosymbiosis

  5. Fig. 25.9

  6. Fig. 25.9

  7. Fig. 25.9

  8. Origin of Life on Earth • Characteristics of Early Life • Eukaryotes • Evidence for serial endosymbiosis • Inner membranes of plastids & mitochondria have enzymes and transport systems similar to those of plasma membranes in modern bacteria • Plastids & mitochondria replicate by binary fission process similar to that of bacteria • Plastids & mitochondria each contain single, circular DNA molecule without histones or other proteins (similar to bacteria) • Plastids & mitochondria have ribosomes that resemble prokaryotic more than cytoplasmic ribosomes (size, sequence, sensitivity to antibiotics)

  9. Geological Record • Rocks, sediments, fossils – Occur in layers (strata) • Oldest fossils – Stromatolites from 3.5 bya

  10. Geological Record • Dating • Index Fossils • Based on common species • Useful for establishing relative ages • Used by petroleum industry • Radiometric Dating • Technique for absolute dating • Based on decay of radioactive elements in rocks

  11. Fig. 25.5

  12. Geological Record • Dating • Index Fossils • Radiometric Dating • Half-life unaffected by temperature, pressure, etc. • Ex:40K 40Ar with t0.5 = 1.3 billion years • Initial rock has 100% 40K and no 40Ar • Rock with 40K:40Ar = 1:1 is 1.3 billion years old • Rock with 40K:40Ar = 1:3 is 2.6 billion years old • Commonly used radioisotopes • 40K with t0.5 = 1.3 billion years • 235U with t0.5 = 704 million years • 14C with t0.5 = 5730 years

  13. Geological Record • Geological Time Scale • Earth’s history divided into periods based on major geological, climatic, & biological changes

  14. Mass Extinction (K-T) First Bird (150 mya) ? Mass Extinction (96% of marine spp.) First Amniote Egg ? ”Age of Fishes” First Land Plants/Animals ? First Fishes

  15. - Siberian Volcanism - Increased CO2 - Altered Ocean Mixing Fig. 25.15

  16. Cretaceous Mass Extinction Fig. 25.16

  17. Time Scale: One Year Homo appears: Dec 31 @ 5 pm Fig. 25.7

  18. Global Plate TectonicsJurassic to Present Day By L.A. Lawver, M.F. Coffin, I.W.D. Dalziel L.M. Gahagan, D.A. Campbell, and R.M. Schmitz 2001, University of Texas Institute for Geophysics February 9, 2001

  19. Earth – Future Drift

More Related