BIOSPHERE The earth without life is an dynamic place, active geologically and climatically, and we assume all this complexity must be consistent with scientific ideas. But the world as it is now also differs dramatically from what we would expect from basic ideas of physics and chemistry. Especially in the composition of the atmosphere. Key question, are gases in ________________ or not? CO 2 - Carbon Dioxide O 2 - Oxygen N 2 - Nitrogen Percent Composition of the Atmosphere CO 2 O 2 N 2 Venus Mars Earth (w/o life) Earth (w/ life) Oxygen gas (O 2 ) is dangerously reactive It can only be maintained by constant input Is something strange happening on earth? If we look a little closer we see This altered atmosphere is visible from space altered _________________ NASA Viewed from space, much of the planet has an unexpected greenish appearance. Of course, this is due to the presence of LIFE in particular, ______________. Global climate modelers refer to this green layer in the biosphere as the __________, a source of annoying complication Lithosphere + Hydrosphere + Atmosphere + LIFE = _________________ Does the presence of life have anything to do with the problem of our bizarre atmosphere? 2-9/2-8 How is it possible that something as humble as LIFE could fundamentally alter something as vast as the atmosphere?? 12-1 How big is the atmosphere? Hardly any air above _____________ How deep is the hydrosphere? Oceans cover about ___% of earths surface Average depth _____m (_______ ft) Deepest depth Mariana Trench, Western Pacific - _________m (________ ft) How tall is the lithosphere surface? Everest (Himalayas) is ______m (________ ft) So this zone where life exists is about __ miles thick 2-9/2-8 Earth is LARGE but Biosphere ______ Earth 8,000 miles in diameter Ocean + atmosphere about 20 miles thick 20/8000 = 1/400 if earth 40cm, biosphere _____ 8,000 Effectively two-dimensional Like the skin on an apple Or a soap bubble Because the biosphere is _____, life (including humans) can play important roles in its dynamics Global patterns of _____________ (CO) _____________, which generates __________ as a by-product, is the source of the __________-rich atmosphere on earth. Major consequences of this change include - potential for ______________ - development of an _______ layer in the atmosphere National Geographic Sunlight in the upper atmosphere interacts with ___________ to produce __________. __________strongly absorbs ___________ waves in the sunlight, which are high energy and potentially damaging to living organisms. Biology is a branch of chemistry, and chemistry is the study of the interactions among elements and molecules. These interactions are generally formulated in terms of ______________________ For example, ozone involves the splitting of an ________molecule (___) into two _________ atoms which then combine with other ________ molecules to form ___________. This interaction is expressed as 3__ => 2___ This is fairly simple because it only involves one element (__) What is Life? Generally reactions involve multiple elements and molecules AB + CD => AC + BD Some molecules have a strong tendency to react together they spontaneously react and release energy called _____________ reactions Other reactions wont run unless energy is added, called ___________reactions Reactants => Products A key feature of a living organism is the capacity to transform ___________ in the environment (________, ________) into ______ (_________________, _________) The two essential classes of resource are 1. _________2. ______ (________) These are essential resources for cells, energy is required to drive_____________ (construction of life from elements). The ultimate sources for these for most life today are 1. _______ the sun, by photosynthesis 2. ____________ earth, sea and air The immediate source of this energy for all known living systems are energy-rich organic molecules. Organic refers to molecules based on _____________ The controlled breakdown of these molecules is ___________ (energy releasing) and coupled to biosynthesis, which requires energy input (__________) C 6 H 12 O 6 or CH 2 O The key event in photosynthesis is when ___________, absorbed by pigments (e.g. ___________ a green pigment), raise the energy state of an _____________. Through an intricate linked series of reactions, the energy of this ______ is used to assemble sugar. Sugar is made from carbon dioxide and water using light! This is often called __________ fixation _______________ light energy stored in sugar (see ch2) CO 2 + H 2 O + light = sugar + O 2 C 6 H 12 O 6 ____________ uses up ____ and releases ____ How does this reaction compare with the anomalous atmosphere we see on earth? Percent Composition of the Atmosphere CO 2 O 2 N 2 Venus Mars Earth (w/o life) Earth (w/ life) Photosynthesis uses up CO 2 and releases O 2 What about nitrogen? (reminder) Most photosynthesis today produces oxygen (O 2 ) as a byproduct (water, H 2 O, is split to obtain the electron). This is called ____________ photosynthesis. Interestingly, there is an alternative pathway that doesnt split water, that re-uses electrons instead, called ______ photosynthesis. Most photosynthesizers today do a small portion of their photosynthesis via the _________ pathway. It is likely that the ________ pathway evolved first. If that mode had persisted, there would be _________ in the atmosphere today, _______. Respiration (aerobic) energy in sugar used for metabolism Sugar + O 2 = Energy + CO 2 + H 2 O Once oxygen increased in the atmosphere, life could make use of its strong reactivity Both fire and respiration have exactly the same reaction equation the oxidation of carbohydrate Respiration is sometimes called a controlled burn where the energy is extracted in small steps to maximize the useful ___________________. Major biochemical pathways and processes in life today Photosynthesis light energy stored in sugar CO 2 + H 2 O + light = sugar + O 2 Respiration energy in sugar used for metabolism Sugar + O 2 = Energy + CO 2 + H 2 O Each is a complex chemical pathway Carbon (& Oxygen) Cycle Life has created new _________cycles in the biosphere Photosynthesis and Respiration create a linked cycling of _____________ between life and the atmosphere -and also a link to the ____________________ cycle. photosynthesis CH 2 O(sugar) respiration O2O2 CO 2, H 2 O That these gases are relatively stable in the atmosphere suggests that these two processes are in_______ a _________________ Wait a minute!! If this is a balanced cycle, why would CO 2 ever go down and O 2 up??? Current view - this is a result of_________of photosynthetically fixed carbon in carboniferous rocks and fossil fuels. - shells of marine animals (______________) create _________ rock like limestone under oceans - accumulation of buried _______material on land creates _____ fuels like coal, shale, petroleum The excess ______ then accumulates in the atmosphere This creates a longer term carbon cycle the buried carbon is not released until ____________ (______, ____) exposes these deposits to oxygen and weathering. It is estimated that this rock weathering combined with volcanic activity are essential to replace the carbon lost by burial thus continued life depends on the _____________ releasing this carbon Carbon Fixation C Deposition C Burial & Compression C Uplift & Weathering 2-20/2-26 These two levels of cycling are well illustrated in this figure, not so well in the current edition The really striking fact here is how life has altered the dynamics not only of the atmosphere, but of the lithosphere as well entirely new kinds of rock. In brief, there is a fast carbon cycle and a slow carbon cycle or maybe we should say slow and slower. Atmospheric CO2 Photosynthesis Respiration Carbonaceous rocks Fossil Fuels Volcanoes Uplift & Weathering Combustion Geology Biology Deposition & Compaction Biological & Geological regulation of CO2 Light photosynthesis CH 2 O (sugar) respiration biosynthesis heat O2O2 CO 2, H 2 O Photosynthesis and respiration transform non-life into life using material and energy. The relation between the two processes expands our generalization about living systems Energy _____ through the system (degraded to heat, light to space ) Energy ______ the cycle Light Materials can ____ indefinitely (are re-used) End