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2012-‐09-‐07 DES 2012 – 1GV043 Biosphere Biological processes Jorijntje Henderiks Room: Fk217 (Paleobiology) The Biosphere week • Monday 8 October – Friday 12 October • Wednesday 10 Oct.: Computer pracUcal (obligatory) • Friday 12 October: Biosphere discussion groups and seminar (obligatory) • 6 groups (at least 4 people per group) • 6 Themes: 1) 2) 3) 4) 5) 6) Global mass exUncUons – lessons from the past Phytoplankton through Ume Land plants and climate The Cambrian explosion “The second climate problem”: Ocean acidificaUon The hunt for modern-‐analogues: Impacts of ocean acidificaUon 1 2012-‐09-‐07 Life as we know it • What makes a habitable planet? Mercury Venus Mars Life as we know it • What makes a habitable planet? Chemistry Atmosphere Energy (radiaUon / heat control) Liquid water (H2O) Extended regions of liquid water, condiUons favorable for the assembly of complex organic molecules, and energy source to sustain metabolism NASA Astrobiology program 2 2012-‐09-‐07 Life as we know it • • • • Atmosphere Hydrosphere, Cryosphere Geosphere Biosphere: Thin crust of life – Corresponding to thickness of thin outer skin of apple? ... More like an orange peel! Life as we know it Friday morning Philosophy: How do we define Life? Self-‐replicaUng molecules, capable of passing on properUes which are subject to natural selecUon 3 2012-‐09-‐07 Environmental condiUons OccupaUon of fundamental niche on a global scale may be precluded by environmental barriers, etc., producing an observed realized niche spa,al and temporal boundaries! Fitness • Fundamental niche • Abundance and spa,al range of a species influenced by e.g. climate and compeUUon var2 var1 Three domains of Life Animals, plants, fungi and proUsts Bacteria, e.g. cyanobacteria Archaea 4 2012-‐09-‐07 Archaea • • • • More closely related to Eukarya than to bacteria? Unique rRNA Unique membrane lipids & cell wall construcUon live in the most extreme habitats in nature, extremophiles Extremophiles • An extremophile is an organism that thrives under "extreme" condiUons. The term frequently refers to prokaryotes and is someUmes used interchangeably with Archaea Methanogen: An organism that produces methane from the reacUon of hydrogen and carbon dioxide, member of the Archaea. 5 2012-‐09-‐07 Extremophiles Hottest 113°C Coldest -15°C Thermophile Pyrolobus fumanii (Vulcano Island, Italy). Earth’s average surface temperature is 15°C Psychrophile Crypotendolithus (Antarctica) Deepest 3.2 km underground underground These bacteria live in the spaces between rock grains in the Earth’s crust and are exposed to high levels of pressure, heat, and radiation Most acidic pH 0.0 Acidophile These bacteria grow in caves. Most life lives within a pH range of 5 to 8. Most basic pH 11 Alkaliphile Highest radiation 5 million rads Alkaliphilic bacteria are found in areas where large bodies of water have evaporated and left behind layers of alkaline minerals Deinococcus radiodurans is a common soil organism. A dose of 1000 rads will kill a person. Less than 1 rad per year is normal. Longest period in space 6 years Highest pressure Piezophile (Barophile) This was a bacillus living at the bottom of the Marianas Trench, the deepest point beneath Earth’s oceans. Typically, atmospheric pressure at sea level is 1013 millibar. Saltiest 1200 times atmospheric pressure 30% salt Halophile Anoxic No oxygen Anaerobe Halophilic bacteria live in water with a 30% salt content. By comparison, seawater and human blood are about 3.5% salt. Fresh water has very little salt. e.g. Sulphur or Hydrogen reducing bacteria. Facultative Anaerobe: An organism that grows in the presence or in the absence of oxygen. Obligate Anaerobe: An organism that cannot grow in the presence of oxygen; the presence of oxygen either inhibits growth or kills the organism. Bacillus subtilis living in a NASA satellite that exposed test organisms to the extreme conditions of outer space Extremophiles Champagne Pool, Waiotapu, New Zealand 75°C High in heavy metals [As] [Sb] [Ti] [Au] [Hg] majority of microbes are related to organisms involved in either hydrogen or sulphur respiraUon 6 2012-‐09-‐07 Extremophiles Champagne Pool, Waiotapu, New Zealand The orange precipitates are underwater and consist of sulphur with high heavy metal content. At the air/water interface sulphur and silica precipitates form that grow into microstromatolites – built by thermophilic bacteria and archaea! Extremophiles Rio Tinto, Spain Extremely low pH (2) in river, despite rain water influx Fernández-‐Remolar et al., 2005 7 2012-‐09-‐07 Astrobiology Rio Tinto, Spain Life on Mars? Fernández-‐Remolar et al., 2005 NASA/JPL-‐Caltech/Cornell University Origin of Life? • 1953 Miller & Urey experiment • Organic molecules (amino acids) result, but more needed to establish life (e.g. organizaUon (on mineral substrate?), self-‐replicaUon …) 8 2012-‐09-‐07 Origin of Life Proteins? Stanley Miller and Harold Urey tried to prove this DNA? too complex can only replicate with the help from RNA (ribonucleic acid) Origin of Life RNA? RNA is simple and… -‐ Can self replicate (pass its coded message on to descendants) -‐ messengerRNA translates the geneUc code and transferRNA collects the correct amino acids for the producUon of proteins. -‐ RNA funcUons as a catalyst as well (enabling proteins to form) 9 2012-‐09-‐07 Origin of Life Life probably (?!) arose somewhere on Earth (?!) from some kind of “primordial soup” of organic molecules in the seawater With Ume, these molecules were concentrated, reacted with each other and formed more advanced molecules like proteins and nucleoUde bases Next and largest step: From the molecules exisUng in the primordial soup it is possible to make cells, genes and enzymes This final step is surrounded by different theories on how it was achieved One main idea: Some organic molecules could assemble into larger structures through their natural construcUon Simple molecules complex molecules self assembly ? system of molecules that traps energy and reproduces 10 2012-‐09-‐07 Some other ideas: Life from outer space? Amino acids, the building blocks of proteins have been found on meteorites It is possible that life originated on another planet, but the problem remains, how and where did life originate? You have just transferred the problem to another locality in the universe Some other ideas: Black smokers? (“Miller & Urey experiment ) 11 2012-‐09-‐07 Some other ideas: Deep in the crust? In summary … Organic material Protocell Last common ancestor Eukaryota Bacteria Archaea 12 2012-‐09-‐07 Three domains of Life Animals, plants, fungi and proUsts Eukaryotes : nucleus and ordered cell structure Bacteria, e.g. cyanobacteria Archaea Prokaryotes (Bacteria and Archaea): no nucleus, no ordered cell structure Three domains of Life Eukaryotes : nucleus and ordered cell structure Note: 1 order magnitude difference in scale!! Prokaryotes (Bacteria and Archaea): no nucleus, no ordered cell structure 13 2012-‐09-‐07 Origin of eukaryoUc organelles The endosymbioUc hypothesis (Lynn Margulis) Mitochondria: aerobic bacteria? Chloroplast: autotrophic symbionts (cyanobacteria)? Hosted by primordial eukaryotes (with nucleus holding DNA) Diagram: Falkowski et al. 2004 EvoluUon of sexual reproducUon • Prokaryote reproducUon by simple fission: evoluUon depends on (rare) mutaUons, many individuals and generaUons, natural selecUon • Eukaryotes have sex: Greater geneUc variety 14 2012-‐09-‐07 EvoluUon of sexual reproducUon • Double set of chromosomes (diploid, 2N), thoroughly shuffled during meiosis (recombinaUon) • Back-‐up copies in case of detrimental mutaUons during life Ume (e.g. protein building) • Fast promoUon of beneficial mutaUons by natural selec,on (see next lectures in October …) To revise ater today’s lecture: in “Earth-‐Life System” (Open University; edited by Charles Cockell): • Chapter 5 (p. 172 – 184) – Eukaryote beginnings, evoluUon, diversificaUon • Mitosis and meiosis (Box 5.3) • EndosymbioUc hypothesis 15 2012-‐09-‐07 How does Life fit in? Classical Geology vs. Earth System Science Life on a Changing Earth • Life is a conUnuum -‐ from the earliest organisms to the great variety of species that exists today • Geological events change the course of biological evoluUon • Conversely, life changes the planet that it inhabits 16 2012-‐09-‐07 Planetary Boundaries Rockström et al., 2009 17
