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  2. 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? CO2 - Carbon Dioxide O2 - Oxygen N2 - Nitrogen

  3. Percent Composition of the Atmosphere CO2 O2N2 Venus Mars Earth (w/o life) Earth (w/ life)

  4. Oxygen gas (O2) is dangerously reactive It can only be maintained by constant input

  5. This altered atmosphere is visible from space – altered _________________ Is something strange happening on earth? If we look a little closer we see…

  6. NASA

  7. NASA

  8. 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

  9. Lithosphere + Hydrosphere + Atmosphere + LIFE = _________________ 2-9/2-8 Does the presence of life have anything to do with the problem of our bizarre atmosphere?

  10. How is it possible that something as humble as LIFE could fundamentally alter something as vast as the atmosphere??

  11. How “big” is the atmosphere? Hardly any air above _____________ 12-1

  12. How deep is the hydrosphere? Oceans cover about ___% of earth’s surface Average depth – _____m (_______ ft) Deepest depth – Mariana Trench, Western Pacific - _________m (________ ft) How tall is the lithosphere surface? Everest (Himalayas) is ______m (________ ft)

  13. So this zone where life exists is about __ miles thick 2-9/2-8

  14. 8,000 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 _____ Effectively two-dimensional Like the “skin on an apple” Or a soap bubble…


  16. Because the biosphere is “_____”, life (including humans) can play important roles in its dynamics

  17. Global patterns of _____________ (CO)

  18. _____________, 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

  19. 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.

  20. What is Life? 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 (__)

  21. Generally reactions involve multiple elements and molecules Reactants => Products AB + CD => AC + BD Some molecules have a strong tendency to react together – they spontaneously react and release energy – called _____________ reactions Other reactions won’t run unless energy is added, called ___________reactions

  22. 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

  23. The immediate source of this energy for all known living systems are energy-rich organic molecules. “Organic” refers to molecules based on _____________ C6H12O6 or CH2O The controlled “breakdown” of these molecules is ___________ (energy releasing) and coupled to biosynthesis, which requires energy input (__________)

  24. 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.

  25. _______________ – light energy stored in sugar (see ch2) CO2 + H2O + light = sugar + O2 Sugar is made from carbon dioxide and water using light! This is often called “__________ fixation” C6H12O6 ____________ uses up ____ and releases ____ How does this reaction compare with the anomalous atmosphere we see on earth?

  26. (reminder) Photosynthesis uses up CO2 and releases O2 Percent Composition of the Atmosphere   CO2 O2N2 Venus Mars Earth (w/o life) Earth (w/ life) What about nitrogen?

  27. Most photosynthesis today produces oxygen (O2) as a byproduct (water, H2O, is split to obtain the electron). This is called “____________” photosynthesis. Interestingly, there is an alternative pathway that doesn’t 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, _______.

  28. Once oxygen increased in the atmosphere, life could make use of its strong reactivity Respiration (aerobic) – energy in sugar used for metabolism Sugar + O2 = Energy + CO2 + H2O 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 ___________________.

  29. Major biochemical pathways and processes in life today Photosynthesis – light energy stored in sugar CO2 + H2O + light = sugar + O2 Respiration – energy in sugar used for metabolism Sugar + O2 = Energy + CO2 + H2O Each is a complex chemical pathway

  30. photosynthesis CH2O(sugar) O2 respiration Carbon (& Oxygen) Cycle Life has created new _________cycles in the biosphere CO2, H2O Photosynthesis and Respiration create a linked cycling of _____________ between life and the atmosphere -and also a link to the ____________________ cycle. That these gases are relatively stable in the atmosphere suggests that these two processes are in_______ – a _________________

  31. Wait a minute!! If this is a balanced cycle, why would CO2ever go down and O2 up???

  32. 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

  33. This creates a longer term carbon cycle – the buried carbon is not released until ____________ (______, ____) exposes these deposits to oxygen and weathering. Carbon Fixation C Uplift & Weathering C Deposition C Burial & Compression 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

  34. In brief, there is a fast carbon cycle and a slow carbon cycle or maybe we should say slow and slower. These two levels of cycling are well illustrated in this figure, not so well in the current edition 2-20/2-26 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.

  35. Biological & Geological regulation of CO2 Atmospheric CO2 Volcanoes Biology Uplift & Weathering Combustion Photosynthesis Geology Respiration Deposition & Compaction Carbonaceous rocks Fossil Fuels

  36. Photosynthesis and respiration transform non-life into life using material and energy. The relation between the two processes expands our generalization about living systems Light Energy _____ through the system (degraded to heat, light to space ) photosynthesis CH2O (sugar) CO2, H2O O2 respiration Materials can ____ indefinitely (are re-used) biosynthesis heat Energy ______ the cycle Light

  37. End