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What is Evolution?
Evolution is the change over time, this is the change of heritable traits from one generation to the next. The concept of evolution is mainly influenced by palaeontology, the descendants from ancestral species are different than that of the present day. Evolution occurs gradually through natural selection, mutation and geneflow. The driving force for evolution is natural selection, natural section occurs when the traits of a specific species are passed to the next generation at higher rates than the traits of other species and they live in their environment and reproduce because of them traits. There are different types of evolution, convergent evolution, co-evolution, divergent evolution. Convergent evolution is when species have similar features but different lineages. In the case of sugar gliders native of Australia, they have similar features to that of the flying squirrel that are native of North America. However, the sugar glider has more characteristics that are similar to that of marsupials. These two individuals have developed from two different ancestors but due to their environment have developed similar characteristics this is due to analogous features. (Campbell et al 2015).
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Divergent evolution is when a species with a common ancestor evolves eventually into a different species. This is the case with crocodilians, dinosaurs and birds thy come from a common ancestor but have evolved into different species. Due to phylogenetic evidence birds have a common ancestor to lizards and crocodiles and dinosaurs. (Campbell et al 2015). Co evolution in when there is a joint evolution of two species. This is mutualistic relationship between two species. For example, a relationship with a pollinating flower and insects.
Give a historical description of how modern evolutionary theory has arisen?
Greek philosophers before Charles Darwin as born believed that life changed over time. They believed in a Bible based idea that was known as Scala Naturae. This concept was predicted that each living thing had a place on this ladder of life. (Kutschera. Ulrich 2011). The study of fossils was developed by Georges Cuvier, he noticed that the older the fossils the more different they were from the living forms of the species. He also discovered that from one generation to the next that some forms of the species would disappear, they noted that extinction was a common event happening from generation to generation. He also denied that species can evolve. (Campbell et al 2015). One of the early concepts of life was carried out by a French Biologist Alas Lamarck, he proposed that each species can inherited acquired characteristics and this was later proven wrong, he believed that an organism could pass on learned traits. ( Burkhardt Richard W. Jr, 2013).
From this then Charles Darwin explained Evolution by natural selection, he explained that species evolve according to their environment. This believed that adaptations were the main aspect of evolution, he believed when a species adapts to its environment to increase their survival rate was essential for the evolution of a species. Charles Darwin also predicted that when a population changes their habitat that natural selection is the main force that that causes the adaptations to occur. In some cases, establishing new species from that change in the environment. The modern theory of evolution combines population genetics, palaeontology and molecular sequencing of DNA. Palaeontology is the main evidence on how organisms have evolved over generations. The Hadean was the beginning of the earth where the crust of the earth began to cool. The cooling of the surface and the gravitational field and magnetic field allowed the earth’s atmosphere to develop. This leads into the Archean era where the first observation of rock, at this time there was also fossils that were observed of cyanobacteria. These fossils give indication of the first life on earth. Proterozoic bacterial fossils and other evidence of life is abundant, the Ediacaran Biota is one of the first fossils found in the metazoan life, it is a mixture of both fungi, bacteria and cnidarians. (MacGabhann B.A 2007).
Describe how evolution can be identified measured and accessed.
Evolution is identified using natural selection as the main area of identification. An example of natural selection at work is the evolution of the antibiotic resistant bacteria. The resistant forms of a bacteria can multiply more quickly in a certain environment. Staphylococcus aureus is a bacterium that is found on the skin along with normal flora and does not cause any effects to humans. However certain strains of this bacterium can cause serious effects to humans. The methicillin resistant S. aureus are harmful pathogens that are a flesh-eating disease. Due to the bacteria constantly mutating to the antibiotic this has caused MRSA to be a very serious disease. The gene alterations in the bacteria is caused by the evolution of the genes to the drugs. (Madigan et al 2015). This example demonstrates Darwin’s theory of natural selection and how evolution can be identified.
The use of Homology is also used for the identification of evolution. Homology is when there are organisms that have similar anatomy due to a similar ancestor. This could be the fact that two organisms have similar organ position. An example of evolution using homology is the forelimb of all mammals. The forelimb of mammals are the same in dog, cows and that of a whale or a bat. They have all the same arrangement of forelimbs.
Figure 1: Homologous structures of forelimbs. (http://bodell.mtchs.org)
According to Cretekos et al 2007 they replaced a limb specific transcriptional enhancer of a mouse with a sequence of a bat. The orthologous sequence of the bat caused elevated transcriptional degrees for the development of forelimbs. Due to the sequence from the bat the forelimbs of the mouse became increasing larger and the bone in the forelimb of the mouse grew longer. This demonstrates that the mutations in the gene sequence of different species caused variation in the evolution of different species. (Cretekos et al 2007).
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The use of fossils s another way for the identification of evolution. The fossil record shows that the organisms that are living today are significantly different than that of the fossil found centuries ago. An example of fossils being used in the identification of evolution is the fossil record of cetaceans and the mammalian group. The data supported DNA sequenced data to show that cetaceans were closely related to deer, pig, camel and cows. (Campbell et al 2015)
Figure 2 : Demonstrates that cetaceans evolved from land animals. (http://theobligatescientist.blogspot.com)
Evolution can be accessed using Molecular Phylogenetics. With the use of molecular phylogenetic protein electrophoresis can be achieved. Protein electrophoresis is a technique that is used for identifying closely related species. The use of DNA-DNA Hybridisation is also used for phylogenetic analysis. This is when the DNA of two different organisms are combined and then denatured and hybrid molecules then are achieved. The hybrid molecules that is stable has a higher melting point than that of an unstable molecule. The melting points obtained provide the data for the phylogenetic analysis. (Brown .Terence 2002). The purpose of Phylogenetic trees is to reconstruct the evolutionary relationships that is between the organisms being studied. This is achieved by choosing the appropriate DNA sequence for the taxonomic level being studied, converting the data into a reconstructed tree. From this then accessing the accuracy of the tree using molecular clocks to assign the dates to the branches of the tree. Molecular clocks are used to measure the amount of time that evolution occurred according to the genes and genomes of the organism. To calibrate the molecular clock the number of genetic differences is graphed, nucleotide, amino acids differences are graphed against the dates of the evolutionary points from the fossil record. The use of molecular phylogenetic is necessary in the assessment of evolution. (Campbell et al 2015)
Evolution can be measured by using the Hardy Weinberg equation. This equation is used with the assumption that there is random mating; no migration between populations, there is a large population large enough so there is no effect on alleles. There are no mutations and no selection in a population. When this criterion is fitted then there is use of Hardy Weinberg equation is used to estimate evolution. This equation is used to detect the genotype frequencies, p² + 2pq + q² = 1, were p2 is the frequency of homozygous dominant, 2pq is frequency of heterozygous and q2 is the recessive homozygous traits. To measure if evolution is occurring there is use of the gene frequencies of a locus, that measures against a non-evolving population. If the allele frequencies are not changing, then is assumed that the population is not evolving. The Hardy Weinberg equation
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