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Define life? or Describe life? The Nature of Life on Earth Life in the Universe Astrobiology Dr. R. L. Hudson (Fall, 2015) Characteristics of Life on Earth Chemistry C H O N Atoms, molecules, ions Non-equilibrium Isolated from surroundings Takes stuff in and moves it out Reproduction, passes on traits Evolves Common Elements and Compounds H C N O CH4 NH3 H2O methane ammonia water Cells Energy Environment Chiral Molecules Mirror Twenty Amino Acids (AAs) Proteins = Chains of Amino Acids Twenty-Five Alanines (20)25 = 340 000 000 000 000 000 000 000 000 000 000 1 Big Question: Double helix Complimentary strands How does biology get it right? A Big Answer: T Chemistry! G DNA, the Master Molecule C DNA’s Protein Synthesis Method (In Brief!) DNA Data A few billion base pairs in the DNA of a cell DNA (our hero) Thousands of base pairs per human gene Total DNA mass … about 0.5 grams DNA in a human cell ~ 2 meters! 1013 cells … 10 billion miles! See page 176. The Genetic Code Simplified version 1. RNA copies ATGC sequence 2. RNA attaches to other molecules, which line up AAs (genetic code) 3. AAs link to give proteins! DNA’s Reproductive Method (In Brief!) 2 DNA is common to all terrestrial life. Earth Life Shares a Common Chemistry 1. CHON + PS DNA is everywhere! DNA is Common to all Terrestrial Life Characteristics of Life on Earth 2. Amino acids 3. Proteins (and enzymes) 4. DNA Chemistry Cells Energy Environment Cells – Also Common! Prokaryote Eukaryote Three Domains of Life 3 Characteristics of Life on Earth Life Needs Energy! Chemistry Cells Energy Environment Plants Use Light – Photosynthesis! 6 CO2 + 6 H2O C6H12O6 + 6 O2 C6H12O6 + 6 O2 Plants Animals ENERGY Animals Use Plants C6H12O6 + 6 O2 6 CO2 + 6 H2O Some Astrobiology Lessons Chemistry – CHON (and PS) Molecule doing DNA’s work 6 CO2 + 6 H2O 6 CO2 + 6 H2O Some Astrobiology Lessons Chemistry – CHON (and PS) Molecule doing DNA’s work Dr. Julius Hibbert Dr. Stephan Jay Gould Cells – Primitive ones Energy – Plant types first 4 Characteristics of Life on Earth Environments Chemistry Cells Energy Environment Extreme Environments Spirochaeta americana, a thermophile Extremophiles Cryophiles: 5 F (-15 C) Cryptoendoliths (Antarctica) news.nationalgeographic.com/news/2003/09/photogalleries/throughthelens/photo3.html http://www.astrobio.net/news/ 5 Halophiles are salt-loving bacteria. Tubeworms Can grow to ~ 9 feet long “Record holders can survive 30% salt, or 9 times human blood saltiness.” Depend on bacteria living inside them “These bacteria convert the chemicals that shoot out of the hydrothermal vents into food for the worm.” http://www.astrobio.net/news/ http://www.ocean.udel.edu/kiosk/riftia.html Desert varnish Methanobacterium thermoautotrophicum, A reddish coating "of clay and iron oxide precipitated by remarkable bacteria” a methanogenic archaeon www.desertusa.com/magdec97/varnish/dec_varnish.html “Methane ice worms …ingest bacteria that feed off of methane hydrate deposits in deep, dark, cold ocean depths.” www.science.psu.edu/iceworms/iceworms.html www.micrbiol.sci.kun.nl/gallery.html Deinococcus radiodurans “… can withstand without loss of viability a dosage that is 3,000 times greater than what would kill a human.” science.nasa.gov/newhome/headlines/ast14dec99_1.htm 6 Spirochaeta americana Many Life-Supporting Environments “... found in … an alkaline, briny oxygen-limited lake in a closed volcanic crater ...” Green = living cells Others = dead cells Hot Bright, Dry Acidic Cold Dark, Wet Basic High Radiation Doses www1.msfc.nasa.gov/NEWSROOM/NSSTC/news/photos/2003/photosN03-007.html An Example Sources of Material Europa, a moon of Jupiter Most of the images used here are either original, from our class’s textbook, or in the public domain. Material not fitting into these categories has been credited in cases where I knew the sources. I will be glad to add any credits missed. Obviously a few othe images are copied from well-known television programs. 7