Posted: Thu Feb 16, 2006 9:02 am
Before the discovery of DNA most scientists beleived that the hereditary information must be in the form of proteins.
Oswald Avery 1944
http://particle.physics.ucdavis.edu/bios/Avery.html
Discovered that DNA was the material which held the hereditary information.
After this discover some scientists continued to beleive that proteins contained the hereditary information simply because the sugar molecules DNA consists of seemed too simple to convey any information.
In 1953 this all changed when Watson and Crick discovered the double helix. This structure allowed researchers to glean at the duplication process, and how the information is stored.
Now it seemed that the decoding of the code of life would soon comence.
But before we get into genetic analysis, let us see what scientists did with Darwins new idea.
Georges Cuvier
http://www.ucmp.berkeley.edu/history/cuvier.html
The founder of vertebrate paleontology, he also developed a classification system of strict divisions of types based on function. A strict opponent of linnean evolution he did not beleive in evolution. He stated that any small changes would render an animal useless and thus would make it unable to survive.
Étienne Geoffroy St. Hilaire
http://www.ucmp.berkeley.edu/history/hilaire.html
Was a proponent that form defines function, one of the first practicioners of teratology, the study of development. Hilaire beleived that all animals shared a body plan. Cuvier found that this idea was not supported by his own studies. In a famed debate on the similarities of cephalopod and vertebrate design Cuvier convincingly argued that these similarities were contrived. Although not an evolutionist he would set the scene for comparative developmental studies.
August Weismann
http://www.britannica.com/eb/article-9076462
Founder of genetics, theorized on how genetic material must pass onto the next generation.
Julian Huxley
http://noosphere.cc/huxleymenu.html
Julian Huxley did some rather interesting studies on embryology and noted the development of embryos of sea squirts and sea urchins.
During the same time mathmeticians were beginning to see how the laws of heredity along with natural selection can account for change within a population.
J.B.S. Haldane
http://en.wikipedia.org/wiki/J._B._S._Haldane
Sewall Wrighthttp://www.harvardsquarelibrary.org/uni ... ewall.html
Sir Ronald Fisher
http://www.mrs.umn.edu/~sungurea/intros ... isher.html
Theodosius Dobzhansky
http://en.wikipedia.org/wiki/Theodosius_Dobzhansky
Studies with ladybugs revealed that individuals within a population had variations which were not needed for the environment they were found in. Leter he discovered that the more successful species tend to have greater variety present in the population.
Hugo de Vries
http://www.nceas.ucsb.edu/~alroy/lefa/deVries.html
Showed that new charachteritics appear suddenly and that they were inheritable.
At this point it is not generally accepted that all life is related only an idea that there is a parent type for each species.
Studies of cell biology soon changed this as it soon became apparant that all multicellular life at the cellular level was strikingly similar. From plants to birds, to paramecium.
Now to cap we have a theory. Evolution is the idea that species change over time and eventually become a new species resulting in all the variety we have on this planet.
What are the mechanisms for this theory?
Natural Selection.
Mutation.
Genetic Drift.
What are some ways that these mechanisms have been tested.
As seen before organisms go through a developmental embryonic or larval stage where a single cell becomes a complex multicellular organism.
The similarities between different species in embryological development were noted early on.
http://www.pbs.org/wgbh/evolution/libra ... 042_03.pdf
Also noted was that alterations early in the development phase has greater impact than changes which occur later in development.
Later discoveries show how mutations cause changes in development.
Many tests were put together to test natural selection, including inlab.
http://www.genetics.org/cgi/content/full/149/1/189
And in the field.
http://intl.sciencemag.org/cgi/content/ ... 7/5451/306
Mutations were found to add variety to a population.
Mostly from studies on rats and fruit flies.
Other studies of isolated pockets of species, lent credence to the idea of genetic drift. Lab experiments confirmed this idea, with the above mentioned discoveries of mutations.
Isolated populations could not share the same mutations.
So to sumarize, the questions posed by Darwins idea were as follows,
Do species change over time?
It would appear that they do. Experiments have shown that new traits occur.
Does natural selection occur?
Experiments have confirmed the mechanism.
How does variation arise?
Through Mutations.
How does natural selection work.
It works by selecting from existing traits.
Is it gradual?
We are assuming so, but this will turn out to be more complicated than originally anticipated.
What about the problems with the phylogenic chart?
At this point we are unaware of how large this problem actually is.
Now we bring up new questions.
How do we go from one form to another? How does a new species form?
Is all life related?
Is evolution gradual?
How do mutations actually work to add traits?
From our earlier discussion we see that the cell is like a controlled lab experiment. Add in some proteins and they will interact with other proteins in the cell in a cascade of reactions.
Proteins are a result of the amino acid chains encoded in the DNA.
The function of a protein is a result of its shape. There are areas of a protein which are functionally unimportant, we will address this next in the next to final section on comparative genetic analysis.
Oswald Avery 1944
http://particle.physics.ucdavis.edu/bios/Avery.html
Discovered that DNA was the material which held the hereditary information.
After this discover some scientists continued to beleive that proteins contained the hereditary information simply because the sugar molecules DNA consists of seemed too simple to convey any information.
In 1953 this all changed when Watson and Crick discovered the double helix. This structure allowed researchers to glean at the duplication process, and how the information is stored.
Now it seemed that the decoding of the code of life would soon comence.
But before we get into genetic analysis, let us see what scientists did with Darwins new idea.
Georges Cuvier
http://www.ucmp.berkeley.edu/history/cuvier.html
The founder of vertebrate paleontology, he also developed a classification system of strict divisions of types based on function. A strict opponent of linnean evolution he did not beleive in evolution. He stated that any small changes would render an animal useless and thus would make it unable to survive.
Étienne Geoffroy St. Hilaire
http://www.ucmp.berkeley.edu/history/hilaire.html
Was a proponent that form defines function, one of the first practicioners of teratology, the study of development. Hilaire beleived that all animals shared a body plan. Cuvier found that this idea was not supported by his own studies. In a famed debate on the similarities of cephalopod and vertebrate design Cuvier convincingly argued that these similarities were contrived. Although not an evolutionist he would set the scene for comparative developmental studies.
August Weismann
http://www.britannica.com/eb/article-9076462
Founder of genetics, theorized on how genetic material must pass onto the next generation.
Julian Huxley
http://noosphere.cc/huxleymenu.html
Julian Huxley did some rather interesting studies on embryology and noted the development of embryos of sea squirts and sea urchins.
During the same time mathmeticians were beginning to see how the laws of heredity along with natural selection can account for change within a population.
J.B.S. Haldane
http://en.wikipedia.org/wiki/J._B._S._Haldane
Sewall Wrighthttp://www.harvardsquarelibrary.org/uni ... ewall.html
Sir Ronald Fisher
http://www.mrs.umn.edu/~sungurea/intros ... isher.html
Theodosius Dobzhansky
http://en.wikipedia.org/wiki/Theodosius_Dobzhansky
Studies with ladybugs revealed that individuals within a population had variations which were not needed for the environment they were found in. Leter he discovered that the more successful species tend to have greater variety present in the population.
Hugo de Vries
http://www.nceas.ucsb.edu/~alroy/lefa/deVries.html
Showed that new charachteritics appear suddenly and that they were inheritable.
At this point it is not generally accepted that all life is related only an idea that there is a parent type for each species.
Studies of cell biology soon changed this as it soon became apparant that all multicellular life at the cellular level was strikingly similar. From plants to birds, to paramecium.
Now to cap we have a theory. Evolution is the idea that species change over time and eventually become a new species resulting in all the variety we have on this planet.
What are the mechanisms for this theory?
Natural Selection.
Mutation.
Genetic Drift.
What are some ways that these mechanisms have been tested.
As seen before organisms go through a developmental embryonic or larval stage where a single cell becomes a complex multicellular organism.
The similarities between different species in embryological development were noted early on.
http://www.pbs.org/wgbh/evolution/libra ... 042_03.pdf
Also noted was that alterations early in the development phase has greater impact than changes which occur later in development.
Later discoveries show how mutations cause changes in development.
Many tests were put together to test natural selection, including inlab.
http://www.genetics.org/cgi/content/full/149/1/189
And in the field.
http://intl.sciencemag.org/cgi/content/ ... 7/5451/306
Mutations were found to add variety to a population.
Mostly from studies on rats and fruit flies.
Other studies of isolated pockets of species, lent credence to the idea of genetic drift. Lab experiments confirmed this idea, with the above mentioned discoveries of mutations.
Isolated populations could not share the same mutations.
So to sumarize, the questions posed by Darwins idea were as follows,
Do species change over time? It would appear that they do. Experiments have shown that new traits occur.
Does natural selection occur? Experiments have confirmed the mechanism.
How does variation arise? Through Mutations.
How does natural selection work. It works by selecting from existing traits.
Is it gradual? We are assuming so, but this will turn out to be more complicated than originally anticipated.
What about the problems with the phylogenic chart? At this point we are unaware of how large this problem actually is.
Now we bring up new questions.
How do we go from one form to another? How does a new species form?
Is all life related?
Is evolution gradual?
How do mutations actually work to add traits?
From our earlier discussion we see that the cell is like a controlled lab experiment. Add in some proteins and they will interact with other proteins in the cell in a cascade of reactions.
Proteins are a result of the amino acid chains encoded in the DNA.
The function of a protein is a result of its shape. There are areas of a protein which are functionally unimportant, we will address this next in the next to final section on comparative genetic analysis.