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Wednesday, April 07, 2010 2:50:44 PM
What Evolution Is
April 7, 2010 - By Josephus - Folsomtelegraph
As I read all these letters to the editors and sometimes addresses by board members to school boards and speeches by political candidates, I notice two things. The subject is very important; and the people that are most passionate about it don’t seem to know what it is. I believe this may help them achieve their political goals. Armed with the following information, no one will ever be able to say to you “You don’t even know what evolution is!”
http://my.folsomtelegraph.com/detail/146688.html
The Theory of Evolution is a scientific explanatory model that describes how the relative frequency of alleles change in subsequent generations of a population of organisms. “Evolution” is a description of these changes. Alleles are forms of DNA found at genetic loci. What that means is, if you were looking at the DNA of a particular organism in a specific spot in its genome, you are looking at an allele. Evolution occurs through four known mechanisms. Recent research in genetics means that a few more may soon be added to the list, but for now, we should talk about the following four; Natural Selection, Mutation, Genetic Drift, and Gene Flow.
The name Darwin and the term “Darwinism” are associated with Natural Selection. The researcher Charles Darwin noticed physical differences in otherwise closely related populations. After making observations in the field, collecting specimens, examining fossils, and doing some experiments in the backyard, he eventually got around to publishing the book we call On the Origin of Species which describes how Natural Selection works to change the physical appearance of organisms over time. One of the things he contemplated in doing this was how Artificial Selection or Breeding, changes the physical appearance or organisms over time. In breeding, a breeder picks a trait they like and keeps the animals that posses it while getting rid of the rest. Over generations, by picking the trait or traits they want, the breeder can change their stock. Mr. Darwin asked himself this question; what if there were no breeder? What of wild animals that are not bred by humans? What are the factors that determine which of those animals has more offspring and which traits show up more prevalent in the next generation? The answer to his question was this; the environment (behavior, access to food, weather, presence or absence of predators, access to mates, and so on) takes on the role of the breeder in determining what traits make it into the next generation of wild animals not manipulated by humans. Unfortunately for Mr. Darwin, doing his best stuff around the time of the Civil War, he was never able to figure out what it was that was being passed from generation to generation, due to technological limitations and the mistake of the scientists of that day not realizing the importance of the research conducted by a man named Gregor Mendel.
The above is Natural Selection or “Darwinism.” The below is the three other mechanisms of evolution which were added to our list of four after Scientists discovered Genetics. The complete list of all four is known as “The New Synthesis” or “Neo Darwinism” or simply as the Theory of Evolution. We can’t really talk about them without pointing out something Mendel discovered; some traits are dominant and some recessive. Because of Meiosis, Genetic Recombination gives us two things to keep track of; Genotype and Phenotype. Genotype is a term that refers to all genetic information in an organism. Phenotype is a term that refers to the genetic information that is expressed on the outside where we can observe it, such as physical appearance, body size, function, behavior, sexual dimorphism, and so on. As it happens, lots of genetic information is conserved in the Genotype where Natural Selection can’t get at it. Because of this, currently unfit traits can linger in a population in the Genotype to be expressed later in the Phenotype if the environmental conditions change.
Mutation is the source of genetic diversity. While a population can conserve diversity and even experience speciation without new mutations, mutation is the source of new genetic information. Much of the language describing mutation seems laden with judgment, for example “mistake” or “error.” This is because what is supposed to happen, when a cell copies its DNA during replication, is a copy. If that doesn’t happen, it’s probably fair to say mistake or error. If the slightly different copy isn’t repaired, we have a mutation. For the purposes of evolution, we need to look at mutations that happen in a very specific place, the Germ Cells. Mutations that happen anywhere else other than in the Germ Cells are not passed on to the next generation. Mutations are harmful, beneficial, or neutral. Those terms are not as self-explanatory as they would seem. What is being described by those terms is the fitness value the changes have on the organism, which means how the changes affect the number of viable offspring the organism produces. Most mutations are neutral, but what is harmful one day can be beneficial the next day, if the environmental conditions change. Natural Selection works to eliminate currently harmful mutations expressed in the Phenotype.
Genetic Drift is much simpler then the other four mechanisms to talk about. Sometimes even an organism ideally suited to the current environmental conditions just doesn’t leave behind as many offspring as a member of their population less suited to the environment. “Accidents Happen.” The effect that “accidents” have on a population depends on the size of the population. Genetic Drift plays a large role in a small population and a small role in a large population.
Gene Flow is the migration of genetic material from place to place. If you have a huge population of organisms occupying a large geographic space, you can see that the organisms on one side will have little contact with organisms on the other side (especially if those organisms are behaviorally territorial). Restriction of Flow can cause Ring Species. This is where, over time, local populations within the larger population have changed so much in their isolation that, while they can still mate with members in the center of the larger population, they cannot mate with members on the other side and produce viable offspring. Further restrictions lead to speciation.
All of the above have been observed and measured in the field and in the lab. The above is the Theory of Evolution and what evolution is. Evolution has nothing to do with what the universe is doing or where life came from, or whatever all else. The Theory of evolution ONLY describes how the relative frequency of alleles change in subsequent generations of populations of organisms.
April 7, 2010 - By Josephus - Folsomtelegraph
As I read all these letters to the editors and sometimes addresses by board members to school boards and speeches by political candidates, I notice two things. The subject is very important; and the people that are most passionate about it don’t seem to know what it is. I believe this may help them achieve their political goals. Armed with the following information, no one will ever be able to say to you “You don’t even know what evolution is!”
http://my.folsomtelegraph.com/detail/146688.html
The Theory of Evolution is a scientific explanatory model that describes how the relative frequency of alleles change in subsequent generations of a population of organisms. “Evolution” is a description of these changes. Alleles are forms of DNA found at genetic loci. What that means is, if you were looking at the DNA of a particular organism in a specific spot in its genome, you are looking at an allele. Evolution occurs through four known mechanisms. Recent research in genetics means that a few more may soon be added to the list, but for now, we should talk about the following four; Natural Selection, Mutation, Genetic Drift, and Gene Flow.
The name Darwin and the term “Darwinism” are associated with Natural Selection. The researcher Charles Darwin noticed physical differences in otherwise closely related populations. After making observations in the field, collecting specimens, examining fossils, and doing some experiments in the backyard, he eventually got around to publishing the book we call On the Origin of Species which describes how Natural Selection works to change the physical appearance of organisms over time. One of the things he contemplated in doing this was how Artificial Selection or Breeding, changes the physical appearance or organisms over time. In breeding, a breeder picks a trait they like and keeps the animals that posses it while getting rid of the rest. Over generations, by picking the trait or traits they want, the breeder can change their stock. Mr. Darwin asked himself this question; what if there were no breeder? What of wild animals that are not bred by humans? What are the factors that determine which of those animals has more offspring and which traits show up more prevalent in the next generation? The answer to his question was this; the environment (behavior, access to food, weather, presence or absence of predators, access to mates, and so on) takes on the role of the breeder in determining what traits make it into the next generation of wild animals not manipulated by humans. Unfortunately for Mr. Darwin, doing his best stuff around the time of the Civil War, he was never able to figure out what it was that was being passed from generation to generation, due to technological limitations and the mistake of the scientists of that day not realizing the importance of the research conducted by a man named Gregor Mendel.
The above is Natural Selection or “Darwinism.” The below is the three other mechanisms of evolution which were added to our list of four after Scientists discovered Genetics. The complete list of all four is known as “The New Synthesis” or “Neo Darwinism” or simply as the Theory of Evolution. We can’t really talk about them without pointing out something Mendel discovered; some traits are dominant and some recessive. Because of Meiosis, Genetic Recombination gives us two things to keep track of; Genotype and Phenotype. Genotype is a term that refers to all genetic information in an organism. Phenotype is a term that refers to the genetic information that is expressed on the outside where we can observe it, such as physical appearance, body size, function, behavior, sexual dimorphism, and so on. As it happens, lots of genetic information is conserved in the Genotype where Natural Selection can’t get at it. Because of this, currently unfit traits can linger in a population in the Genotype to be expressed later in the Phenotype if the environmental conditions change.
Mutation is the source of genetic diversity. While a population can conserve diversity and even experience speciation without new mutations, mutation is the source of new genetic information. Much of the language describing mutation seems laden with judgment, for example “mistake” or “error.” This is because what is supposed to happen, when a cell copies its DNA during replication, is a copy. If that doesn’t happen, it’s probably fair to say mistake or error. If the slightly different copy isn’t repaired, we have a mutation. For the purposes of evolution, we need to look at mutations that happen in a very specific place, the Germ Cells. Mutations that happen anywhere else other than in the Germ Cells are not passed on to the next generation. Mutations are harmful, beneficial, or neutral. Those terms are not as self-explanatory as they would seem. What is being described by those terms is the fitness value the changes have on the organism, which means how the changes affect the number of viable offspring the organism produces. Most mutations are neutral, but what is harmful one day can be beneficial the next day, if the environmental conditions change. Natural Selection works to eliminate currently harmful mutations expressed in the Phenotype.
Genetic Drift is much simpler then the other four mechanisms to talk about. Sometimes even an organism ideally suited to the current environmental conditions just doesn’t leave behind as many offspring as a member of their population less suited to the environment. “Accidents Happen.” The effect that “accidents” have on a population depends on the size of the population. Genetic Drift plays a large role in a small population and a small role in a large population.
Gene Flow is the migration of genetic material from place to place. If you have a huge population of organisms occupying a large geographic space, you can see that the organisms on one side will have little contact with organisms on the other side (especially if those organisms are behaviorally territorial). Restriction of Flow can cause Ring Species. This is where, over time, local populations within the larger population have changed so much in their isolation that, while they can still mate with members in the center of the larger population, they cannot mate with members on the other side and produce viable offspring. Further restrictions lead to speciation.
All of the above have been observed and measured in the field and in the lab. The above is the Theory of Evolution and what evolution is. Evolution has nothing to do with what the universe is doing or where life came from, or whatever all else. The Theory of evolution ONLY describes how the relative frequency of alleles change in subsequent generations of populations of organisms.
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