MIT Department of Biology 7.014 Introductory Biology, Spring 2005 7.014 Lecture 16: Introduction to Ecology and the Biosphere March 11, 2005 Figure by MIT OCW. 1 Image is taken from NASA's Web site: http://www.nasa.gov. Figure removed due to copyright reasons. Please see: figure 50.12a in Freeman, Scott. Biological Science. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239. 2 Figure removed due to copyright reasons. Please see: figure 50.12 in Freeman, Scott. Biological Science. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239. NITROGEN FIXATION Nitrogenase Enzyme Substrate, N2 N N N N N N H Binding of Substrate H Reduction +2H N N N H H Reduction +2H N N H H Reduction +2H N N Free Nitrogenase can Bind Another Molecule of N2 Release of Product H H H N H H Product: Ammonia, NH3 N H Figure by MIT OCW. 3 The Global Nitrogen Cycle 1 Gt “gigaton” gigaton” Industrial N fixation 100 = = = 109 ton 1015 g 1 billion Gigatons yr-1 <3 fixation by lightening ATMOSPHERE 200 denitrification 140 biological fixation 110 denitrification 36 river flow 15 biological fixation groundwater 1200 internal cycling 8000 internal cycling 10 burial SOIL OCEANS Nitrogen “Cycle” Without Microbes Industrial N fixation 100 <3 fixation by lightening ATMOSPHERE 200 denitrification 140 biological fixation 140 denitification ? 15 biological fixation river flow groundwater 1200 internal cycling 8000 internal cycling ? burial SOIL OCEANS 4 Life on Earth Today: Abridged (Photosynthesis = Respiration) Solar energy Photosynthesis Plants Phytoplankton CO2 + H2O carbon dioxide gas water Chemical energy or heat N,P,S,Fe…. “CH2O” + O2 organic oxygen carbon (mass) Respiration Animals Bacteria Figure removed due to copyright reasons. Please see: figure 6.9, 7.10a, and 7.13 in Freeman, Scott. Biological Science. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239. 5 Image is taken from NASA's Web site: http://www.nasa.gov. 6 CO2 Concentration in Atmosphere (parts per million) Emergent Property R >P P>R Year Image is taken from NASA's Web site: http://www.nasa.gov. EARLY Life on Earth: Abridged (Photosynthesis > Respiration) Solar energy Photosynthesis Plants Phytoplankton CO2 + H2O carbon dioxide gas water Chemical energy or heat N,P,S,Fe…. “CH2O” + O2 organic oxygen carbon (mass) Respiration Animals Bacteria 7 CO2 + H2O Today: Release of Fossil Carbon Dinosaurs 2 Development of Ozone Shield Oxygenic Phototrophs (cyanobacteria) 3 Anoxygenic Phototrophs (photosynthetic bacteria) 10% Prokaryotes 1% Archaebacteria Eukaryotes Eubacteria 0.1% Banded Iron Formations Modern Eukaryotes Carbon Burial Billions of Years Before Present 20% 1 Red Beds 21% Metazoans Marine Origin Terrestrial Origin 0 "CH2O" + O2 % O2 in Atmosphere Origin of Life - 3.8 Billion Years Ago 4 Chemical Evolution Photochemical Synthesis Formation of Earth 4.5 Billion Years Ago Figure by MIT OCW. Figure removed due to copyright reasons. Please see: figure 25.7 in Freeman, Scott. Biological Science. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239. 8 Present Day Planetary Atmospheres Mars Earth Venus CO2 95 % 0.035 % 98 % N2 2.5 % 78 % 2% O2 0.25 % 21 % Trace H2O 0.1 % 1% 0.05 % Temp (°C) -53 16 474 Adapted from Slesinger, W. 1991. Biogeochemistry: An Analysis of Global Change. Academic Press. P.34 The same processes operate at all scales Figures removed due to copyright reasons. Cell BIOSPHERE Figure by MIT OCW. 9 Molecular Ecology Viewing the Biosphere as a network of genes ag tt ca t Is… A Network of Genes (“dissolved information”) agt tc c taa t 1 billion microbes per liter 99.9 % have not been cultivated c tt ag ag tta at ag t ctaa t at ta information content of 1 liter = that in human genome gt t taa cc a tt cc t t ag at ta c t ag a c ct aa t most of unknown function tc ct aa t at ct a ttc ag A Sea of Organsims 10 Cover of Wired Magazine featuring photo of Craig Venter, August 2004, removed due to copyright considerations. Screenshots of the Sorcerer II web site have been removed due to copyright considerations. Please see: http://www.sorcerer2expedition.org/version1/HTML/main.htm 11 Take Home Messages ¾ Ecology – life at different scales ¾ Emergent Properties ¾ Organism ↔ Environment TWO WAY ¾ Life has shaped Earth’s features ¾ Biosphere - geosphere have co-evolved ¾ Genetic inventory unknown ¾ Microbes Rule! 13