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Bio Notes 1.doc

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Department
Biology
Course Code
BIO1130
Professor
All

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An Explanation for the Cambrian ExplosionFour ideas were put other there for the Cambrian explosion most likely all of them are responsible One is the planet froze solid all the experiments of multicellular life were put on hold and by the time snowball earth ends and conditions returned to conditions that allowed for diversity to occur the planet is rich in ability to allow diversity There is the concept of burrowing and shelled armsLate Proterozoic 650MaSnowball earth is a period about 650 millions ears ago 150 million before the cambrian that the earth is believed to be frozen solid There are thoughts that this is a cyclic event that the earth froze then thawed three times The whole of that planet freezes solid The question is why did it happen and how do we know it happened If you go to the period of time in the late Proterozoic we have the single continent straddling the equator that emerged out of the ancient oceans first continent with nothing on it just pure rock Its at the equator the equator is warm and rainy where for the first time we have a sufficiently large land mass and its eroding from the rain and into the oceans are calcium salts and minerals from this continent So we get a huge amount of calcium slowly being built up in the oceans In the oceans there is a balance of CO2 in the air and carbon in the ocean the balance is simply that when CO2 dissolves in water there is a reaction that creates carbonate that will dissociate into protons and bicarbonate this happens all the time Normally it would be in equilibrium but at the time of snowball earth there is a large amount of calcium and this calcium reacts with the bicarbonate atoms to become a solid that sediments This is where we get sedimentary rock This reaction gets even more pronounced if we get silica this will really drive the reaction Since there is an equilibrium between how much CO2 is in the air and water if were removing the carbon to carbon silicon compounds and carbon bicarbonate compounds that means water will absorb more CO2 from the air The first calcium that appears combines from silicon and other minerals that come from the erosion from the first land mass acts as a carbon sink carbon is being pulled out of the air on the whole globe and the level of CO2 starts to fall What do we know as CO2 as today What do we call it A green house gas Were all worried about this CO2 is an important insulate blanket for the earth CO2 is whats keeping heat in If were slowing thinning the CO2 layer from mineralization of the erosion of the first continental land mass as the CO2 levels fall the insulate blanket becomes less insulating and the world starts to coolYou combine it during the Proterozoic where the bloom of algae oxygenated the atmosphere which is a great thing which we got aerobic metabolism The other greenhouse gas was methane which insulated the earth at the time it reacts with oxygen and is destroyed So we were removing the CO2 because of the first land mass that come out of the ocean and that O2 production at the end of the Proterozoic that created and aerobic world was destroying one of the green house gases that was keeping the world warm resulted in ice being formed at the poles Ice is white and reflective as the ice increases the planet is not absorbing heat from the sun so we end up removing the insulate blanket we cover the earth with a blanket of ice that reflecting the suns rays What is believed is that there was a tipping point where the ice got to a point where the ice cap were so large that it got to a point where the earth was unable to compensate for absorbing radiant heat from the sun and the whole thing went into a spontaneous self generating mode and the plant became covered in ice This is what we called snowball earth This has appeared to happen three times The ice will melt there are still things living in the oceans they are under stress no sunlight reaching the oceans We still got the kimo litho tropes We still get volcanic activity and eruptions Over time there will be enough co2 released replace the green house gases and as the green house gases gets replacedthe snow starts to melt and ice starts to melt The interface where the melted planet and the ice is important because there is so much radiant heat being absorbed adjacent to the ice that it speeds up the process What will happen is that co2 will vent out of the ocean and slowly put the blanket back in place and the ice will start to recede as it recedes it ill recede the fastest at the interface of the ice and land This is what is happening up in the arctic now Everyone is mystified on how fast all the glaciers are retreating and how fast the ice mass are retreating its because of the nature between the interface between the ice and the land Thats why the global warming effect is so severe up in the arctic and happening very quickly It will take 100s of 1000s of years for the ice to retract and it will ultimately retract There is debate if the earth was
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