Download
22 4 early life on earth n.
Skip this Video
Loading SlideShow in 5 Seconds..
22.4 – Early Life on Earth PowerPoint Presentation
Download Presentation
22.4 – Early Life on Earth

22.4 – Early Life on Earth

538 Views Download Presentation
Download Presentation

22.4 – Early Life on Earth

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. 22.4 – Early Life on Earth

  2. Origin of Life • Bombardment from outer space prevented life from developing on Earth until at least 3.9 billion years ago (BYA) • Where and how the first life-form developed, however, remains an active area of research

  3. Origins of Life • Earliest atmosphere contained hydrogen, methane and ammonia • This atmosphere + energy supplied by lightning would give rise to organic matter in shallow oceans

  4. Primordial Soup • Miller & Urey devised an apparatus to test this hypothesis in 1953 • Within one week their apparatus had produced organic molecules • Organic molecules included amino acids, the building blocks of proteins (& life) http://www.pas.rochester.edu/~afrank/A105/LectureXVII/FG28_002.PCT.jpg

  5. http://www.centauri-dreams.org/wp-content/uploads/2007/07/interstellar_chemistry.jpghttp://www.centauri-dreams.org/wp-content/uploads/2007/07/interstellar_chemistry.jpg Other Scenarios • Amino acids organized somewhere else in the universe and were brought to earth by asteroids or comets • Chemical synthesis of organic molecules is possible in interstellar clouds • Amino acids have been found in meteorites

  6. http://www.rsc.org/images/b820577a-350-FOR-TRIDION_tcm18-145077.jpghttp://www.rsc.org/images/b820577a-350-FOR-TRIDION_tcm18-145077.jpg Other Scenarios • Amino acids originated deep in Earth or its oceans • Conditions there are favorable for chemical synthesis • Organisms have been found at depths exceeding 3 km

  7. Other Scenarios • Possibility that life emerged deep in the ocean at hydrothermal vents http://www.divediscover.whoi.edu/images/vent_chemistry.jpg

  8. http://www.astrochem.org/endoexo.jpg

  9. Essential Characteristic of Life • Ability to reproduce • All cells require RNA and DNA to reproduce • Recent experiments suggest that RNA molecules might have been the first replicating molecules on Earth http://www.odec.ca/projects/2004/mcgo4s0/public_html/t3/DNA-RNA_strcture.gif

  10. Proterozoic Life • Nuclei are separate compartments that contain RNA and DNA • Prokaryotes = Organisms that do not contain nuclei • Eukaryotes = Organisms whose cells contain RNA and DNA in nuclei

  11. Simple Eukaryotes • Can be unicellular or multicellular • Because they contain nuclei and other internal structures, they are larger than prokaryotes • Extinction came from a widespread glaciation event 750 million years ago (mya)

  12. http://io.uwinnipeg.ca/~simmons/16cm05/1116/28-04-EukaryoteOrigin-L.gifhttp://io.uwinnipeg.ca/~simmons/16cm05/1116/28-04-EukaryoteOrigin-L.gif

  13. Multicellular Organisms • About 630 mya, the climate warmed dramatically and the first multicellular organisms appeared in the oceans • Fossils first discovered in 1947 in Australia • Collectively called the Ediacaran biota, these fossils show the impressions of large, soft-bodied eukaryotes.

  14. Edicaran biota • Seemed to answer the question of why there are no fossils of organisms that existed during the first period of the Paleozoic era https://www.nampost.com.na/shop/products_pictures/eriacaran-fosils-2008.jpg

  15. Edicaran Fossils • In recent years, geologists have found Ediacaran fossils in all parts of the world. • Flourished between 630 mya and 540 mya. • Mass extinction = most of them disappeared • More likely related to present-day organisms began to inhabit the oceans

  16. In-Class Assignment/Homework • WKT 22.4 • AND pg. 641-2 #1-23 • Answer on the back of WKT 22.4