Mrs. Darth Vader
04-11-2010, 05:55
Chapter five deals with the genes. It deals with the DNA. The DNA is a double helix ladder. This molecule is long and intertwined. All along the strands are smaller molecular building blocks called nucleotides. These four different nucleotides are represented by A, C, G, T, letters of the alphabet which stands for their chemical names. These letters make up the “rungs” of the inner part of the double helix ladder. When an unzipping enzyme unzips half of the ladder, it is split in the middle parts of the ladder “rungs”. Then another enzyme comes and puts the two halves back together making two ladders where one was before. This is how the DNA replicate themselves. Now instead of one pair of DNA strands you have two pairs of DNA strands. Sagan explains in detail how the DNA strands works and how everything is made by this double helix ladder. Sagan explains how conservative and slow to change the DNA is by giving examples of a moth and a lobster still have DNA things in common even though it has been a very long time ago since they had a common ancestor.
A proof reading enzyme puts the double helix back together. Usually this is copied exactly but occasionally a set of new instructions are put in place of the old. Usually this causes a mutation which is harmful to the organism and it leaves fewer off spring or no off spring. Occasionally the change makes it so the organism is better equipped to survive, hence it has many off spring. Sagan goes into great detail about how the DNA sequences function. He even gets into parts of the DNA between a STOP order and a START order that seem to have no function. Here it is actually best to read the book for your self because here is great detail. My summery about “Shadows Of Forgotten Ancestors” is just to give you an idea of what is in this very rich and informative book. Hopefully this will get your interest up so you read it your self..
Sagan then shows you how all life is connected on a molecular level and how we do in fact have a common ancestor ( though microbial ) but none the less, the daddy of all that lives on earth.
“This is a principle means by which life evolves-exploiting imperfections in copying despite the cost. It is not how we would do it. It does not seem to be how a deity intent on special creation would do it. The mutations have no plan, no direction behind them; their randomness seems chilling; progress, if any, is agonizingly slow. The process sacrifices all those beings who are now less fit to perform their life tasks because of the new mutation-crickets who no longer hop high, birds with malformed wings, dolphins gasping for breath, great elms succumbing to blight. Why not more efficient, more compassionate mutations? Why must resistance to malaria carry a penalty in anemia? We want to urge evolution to get where it’s going and stop the endless cruelties. But life doesn’t know where it’s going. It has no long term plan. There’s no end in mind. There’s no mind to keep an end in mind. The process is opposite of teleology. Life is profligate, blind, at this level unconcerned with notions of justice. It can afford to waste multitudes.” Page 84 “Shadows Of Forgotten Ancestors” by Carl Sagan.
Sagan also answers why some people live longer than other people. As one would have suspected, living long is in the genes. “Longevity and DNA repair are connected” Also in “Shadows Of Forgotten Ancestors”. If an organism can repair itself more thoroughly and quickly, it will out live one that can not. Here is proof it is blind dumb evolutionary luck that makes you live long. No God making a decision to spare you over someone else. Sagan then shows how the environment acts as a catalyst for changes and adaptations to take place. During stable times DNA sequences that accurately copy itself and are resistant to mutations are selected For. During times of environmental change, DNA sequences that are more pliable and mutate more frequently are selected For. This selection happens by accident when the organism is preserved by its ability to survive. Those less fit are eaten or die young. Sagan then compares Biology to history because accidents and chance have a far bigger role in Biology than physics. Physics have laws that determine the out come of events but Biology is like the world of Quantum Mechanics. The dice, in Biology is rolled far more times than in physics.
Sagan then introduces you to the RNA molecule. The RNA Molecule is single stranded. It does not unzip to copy itself. It can be in a variety of shapes. The RNA molecule serves as a binder to put together molecules that would other wise stay apart. The RNA molecule can get things started. It can be a catalyst. RNA is more wily nily than DNA. RNA also does multi-tasks. DNA is more specialized. Then Sagan ends the chapter with a discussion on over population and the short sightedness and lack of planning of the evolutionary process.
“When the numbers are small, organisms may only infrequently come into competition; but after exponential replication, enormous populations are produced, stringent competition occurs, and a ruthless selection comes into play. A high population density generates circumstances and elicits responses different from the more friendly and cheerful lifestyles that pertain when the world is sparsely populated.” page 95 Shadows Of Forgotten Ancestors” by Carl Sagan.
“You can see the process tends to be adventitious, opportunistic-not foresighted, not with any future end in view. The evolving molecules do not plan ahead. They simply produce a steady stream of varieties, and sometimes one of the varieties turns out to be slightly improved model. No one-not the organism, not the environment, not the planet, not “nature”-is mulling the matter over.
This evolutionary short sightedness can lead to difficulties. It might for example, cast aside an adaptation that is perfectly suited for the next environmental crisis a thousand years from now (about which, of course, no one has a glimmering). But you have to get from here to there. One crisis at a time is life’s motto.” Page 96 “Shadows Of Forgotten Ancestors” by Carl Sagan.
A proof reading enzyme puts the double helix back together. Usually this is copied exactly but occasionally a set of new instructions are put in place of the old. Usually this causes a mutation which is harmful to the organism and it leaves fewer off spring or no off spring. Occasionally the change makes it so the organism is better equipped to survive, hence it has many off spring. Sagan goes into great detail about how the DNA sequences function. He even gets into parts of the DNA between a STOP order and a START order that seem to have no function. Here it is actually best to read the book for your self because here is great detail. My summery about “Shadows Of Forgotten Ancestors” is just to give you an idea of what is in this very rich and informative book. Hopefully this will get your interest up so you read it your self..
Sagan then shows you how all life is connected on a molecular level and how we do in fact have a common ancestor ( though microbial ) but none the less, the daddy of all that lives on earth.
“This is a principle means by which life evolves-exploiting imperfections in copying despite the cost. It is not how we would do it. It does not seem to be how a deity intent on special creation would do it. The mutations have no plan, no direction behind them; their randomness seems chilling; progress, if any, is agonizingly slow. The process sacrifices all those beings who are now less fit to perform their life tasks because of the new mutation-crickets who no longer hop high, birds with malformed wings, dolphins gasping for breath, great elms succumbing to blight. Why not more efficient, more compassionate mutations? Why must resistance to malaria carry a penalty in anemia? We want to urge evolution to get where it’s going and stop the endless cruelties. But life doesn’t know where it’s going. It has no long term plan. There’s no end in mind. There’s no mind to keep an end in mind. The process is opposite of teleology. Life is profligate, blind, at this level unconcerned with notions of justice. It can afford to waste multitudes.” Page 84 “Shadows Of Forgotten Ancestors” by Carl Sagan.
Sagan also answers why some people live longer than other people. As one would have suspected, living long is in the genes. “Longevity and DNA repair are connected” Also in “Shadows Of Forgotten Ancestors”. If an organism can repair itself more thoroughly and quickly, it will out live one that can not. Here is proof it is blind dumb evolutionary luck that makes you live long. No God making a decision to spare you over someone else. Sagan then shows how the environment acts as a catalyst for changes and adaptations to take place. During stable times DNA sequences that accurately copy itself and are resistant to mutations are selected For. During times of environmental change, DNA sequences that are more pliable and mutate more frequently are selected For. This selection happens by accident when the organism is preserved by its ability to survive. Those less fit are eaten or die young. Sagan then compares Biology to history because accidents and chance have a far bigger role in Biology than physics. Physics have laws that determine the out come of events but Biology is like the world of Quantum Mechanics. The dice, in Biology is rolled far more times than in physics.
Sagan then introduces you to the RNA molecule. The RNA Molecule is single stranded. It does not unzip to copy itself. It can be in a variety of shapes. The RNA molecule serves as a binder to put together molecules that would other wise stay apart. The RNA molecule can get things started. It can be a catalyst. RNA is more wily nily than DNA. RNA also does multi-tasks. DNA is more specialized. Then Sagan ends the chapter with a discussion on over population and the short sightedness and lack of planning of the evolutionary process.
“When the numbers are small, organisms may only infrequently come into competition; but after exponential replication, enormous populations are produced, stringent competition occurs, and a ruthless selection comes into play. A high population density generates circumstances and elicits responses different from the more friendly and cheerful lifestyles that pertain when the world is sparsely populated.” page 95 Shadows Of Forgotten Ancestors” by Carl Sagan.
“You can see the process tends to be adventitious, opportunistic-not foresighted, not with any future end in view. The evolving molecules do not plan ahead. They simply produce a steady stream of varieties, and sometimes one of the varieties turns out to be slightly improved model. No one-not the organism, not the environment, not the planet, not “nature”-is mulling the matter over.
This evolutionary short sightedness can lead to difficulties. It might for example, cast aside an adaptation that is perfectly suited for the next environmental crisis a thousand years from now (about which, of course, no one has a glimmering). But you have to get from here to there. One crisis at a time is life’s motto.” Page 96 “Shadows Of Forgotten Ancestors” by Carl Sagan.