FACTORS THAT DRIVE A CHANGE IN ALLELE FREQUENCE.
Mutation
A mutation is a change in DNA. The three types of mutations are substitution, addition, and deletion. In substitution a nitrogen base in copied into a different nitrogen base. In addition a nitrogen and in deletion a nitrogen base is deleted. These mutation could be caused by uv rays and even x-rays. Two examples of mutations caused by x-rays is sickle-celled anemia and albinism. In a mutation a change in a codon occurs causing a change in the amino acid sequence. These changed finally affect the type of protein that is made. Substitution is the less harmful reason because the number of codons stays the same and many sequence of codon represent the same amino acid so the same protein intended to me made can still be made.
A mutation can be harmful or helpful. For example a frog could have a mutation that causes it to have three legs. This could be helpful if the frog loses a leg because it has an extra one. However the extra leg could cause the frog to move slowly preventing it to get food and to escape predators. A mutation must also be heritable in order to be passed down to an offspring. For example a mutation on an anilas skin will not be passed on to the offspring because it is not a mutation in the sex cells. Mutatons also may or may not affect reproductive success. For example blue eye, which are a result of mutation do not affect reproductive success. [class notes] Some Evidence of EvolutionThere are many examples of evolution. Evidence of evolution can be seen in fossil layers, ancient organism remains, similarities among living organism, and similarities of embryos[1]. Fossil are organisms that once lived that have been turned into sedimentary rocks due to pressure of sediments on top of them[1]. Fossil aid in scientist discovering which organism evolved before others. Ancient animal remains can also be found embedded in fossils. Ancient animals such as the mammoth has been discovered in frozen ice also[1].
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Genetic Drift
Genetic Drift is a random change in allele frequency. Two example of Genetic Drift are the Founders Effect and Population Bottleneck. The Founder Effect is the result of an organism moving to a new area. In the general population organism with lot of alleles live together. On organism moves to a different environment in which it reproduces increasing the number of organism with the allele that is carries. For example in the Amish population*Population Bottleneck is the result of an extreme and rapid environment change. A natural disaster like an volcanic explosion causes some organism to die in an environment. The net generation in the environment would be produced by the "lucky" organism that survived the volcanic explosion. The organisms that survived did not survive due to their adaptations but just by luck.
Founder Effect Population Bottleneck |
Migration
Migration also known as Gene Flow is when a group of individuals move from on population to another. Migration results in different gene pools mating leading to the alteration of allele frequencies[1]. The population can migrate over a landscape like a mountain or even across a road.
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Natural Selection
Natural Selection is the idea of "survival of the fittest". Those best suited for the environment survive and reproduce. This idea was described by Charles Darwin. The three types of Natural Selection are Stabilizing Selection, Directional Selection, and Disruptive Selection [1]. Directional Selectional occurs when selection favors one extreme trait over other extreme traits. This results in a change of the mean value of the trait [2]. Unlike Directional Selection, Disruptive Selection occurs when natural selection favors the extreme trait over the intermediate trait[2]. This results in the population being into two different groups and the variance to increase[2]. Stabilizing Selection is the opposite of Disruptive Selection. Natural Selection favors intermediate traits over extreme traits resulting in a decrease in genetic variation[2].
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THE ATLANTIC STURGEON
How Has It Evolved?
SPECIAL ADAPTATIONS
- Instead of scales, the Atlantic Sturgeon has five rows of large bony plates called scutes. The scutes provide protection from predators and sharp objects in the ocean such as coral.[1]
- Atlantic Sturgeons are toothless and bottom feeders. They drag their barbels(whiskers) along the bottom of the water then extend their tubular mouth to suck the food in. Their muscular stomach ground the food.[2]
- Sturgeons have been around for more then 100 million years. According to Rabosky, tyhe Atlantic stugeon, consisting og 29 species, has a great variaety in body sizes.[3]