Lecture 22 Tuesday, November 27, 2007 1. Development of the Ecosphere: Timeline and processes occurring a. 15 billion years ago… i. Big-Bang b. 4.6 billion years ago…… i. Solar systems & earth was formed c. 3-4 billion years ago… i. Oceans and lands were formed ii. Continents started to form d. 3.1-3.5 billion years ago… i. First evidence of life..(single cells bacteria, algae) 2. What is life?? What were the conditions for life? a. 4 billion years ago…… i. The atmosphere was made off: ii. Water vapor iii. Ammonia (NH3) iv. Methane (CH4) v. Hydrogen sulfide (H2S) vi. Hydrogen gas (H2) vii. Carbon monoxide (CO) viii. **Very little O2 & N2 b. 3.1-3.5 billion years ago… i. Single cells algae were able to 1. Anaerobic metabolism (produce E w/out O2) 2. Take C-H20(simple organic molecules) CO2 + alcohols & energy ii. For ~800 millions of years, CO2 was released (as by-products of the metabolism) & built up in the atmosphere and oceans c. 2.3 billion yrs ago….There was enough CO2 in the atmosphere to sustain life…. i. Single-cells (blue-green algae) photosynthesis CO2 + H2O--CH2O + O2built up ii. Initially, the released O2 was lethal to the living organisms (terminar la idea) d. 1.9 billion yrs ago….. i. Ozone (O3) layer is being built in the stratosphere1. Filters out the UV radiation make life possible on land development of O2 tolerant organisms e. 1.3 billion yrs ago…. i. Aerobic respiration CH2O + O2 CO2 + H2O f. 600 mill yrs ago….. i. Life is widespread in the oceans 1. Single cells 2. Early fishes 3. Large algae g. ~420 mill yrs ago…. i. Life is widespread on Land 1. Earliest plants 2. Invertebrates 3. Vertebrates h. ~350 mill yrs ago… i. Development of tropical rainforest fossil fuel today’s oil i. ~200 mill yrs ago… i. Colonization of larger vertebrates 3. One of those (smaller) vertebrates were our ancestors: a bit of ourselves.. a. Date of Separation according to Mitochondrial DNA & Genoma Differences b. Early Human Phylogeny 4. How we have modified our environment at various scales? a. Expansion of Human Habitat (old theory) 5. At 18,000 years ago, the Earth looked like …. 6. Food Chain of Land Animals 7. World Population Trend from 10,000 B.C. to 200 A.D. 8. Traditional modification of our environment at a. local scale b. (Less) Traditional modification of our environment at global scale9. World Population Trend from 10,000 B.C. to 2000 A.D. 10. UN, World Population Prospects a. 1992 b. 2006 11. Malthus’ Population collapse predictions 12. First civilization (self)-collapse.. a. Eastern Island (Cultural & physical aspects) b. Mayas Empire (Cultural & physical aspects) 13. Why has climate change? a. Natural Climate anomalies b. Meteorite impacts (very infrequent & random) c. Hugh Volcanic eruptions (more frequent, but still random) d. Enough evidence of glacial and interglacial periods for the last 2-3 mill yrs 14. Milanković cycles and glaciation a. Performed detailed calculations concerning the periodicity of the earth’s orbital parameters b. Precession: 23,000 yrs i. It’s a ‘slowing down’ of the rotation of the earth tilt of the earth point to various directions (like the axe of a spinning top) c. Axial tilt: 41,000 yrs i. The greater the angle of the tilt the greater the potential for extremes in seasonal climate (especially for polar regions) d. Eccentricity: 100,000 yrs i. During periods of high eccentricity higher differences between max & min distance from sun to earth more potential for extreme (cold & warm) climate 15. Evidence of glaciations? a. Alps b. Home 16. How do scientists track glaciation? a. Stable-isotopes from zooplankton (tiny shells of calcite)b. Come from seawater c. Once dead built up on the ocean bottom as layers (~2.5 cm or 1” = 1,000 yrs) d. Lighter Oxigen (16O) evaporates with water vapor (due to insolation) and then precipitates as either: a) rain and returns with rivers and groundwater to oceans seawater remains the ~same (interglacial) [e.g. now] Or b) snow and accumulates and does NOT return to oceans seawater change rate between 16O & 18O 17. Comparison between O2 isotope record & Milanković cycles 18. If current changes have happened in the past, so what? a. Current rates and scales of these changes are unprecedented on earth b. Natural changes increasingly influenced by “we”, may rapidly create new conditions at the planet scale i. triggering erratic jumps that are hard to predict and understand ii. enhancing feedback loops that weaken these prediction efforts even
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