Molecular Homology
Homology is one of the methods used as evidence for evolution. This term has changed over time as researchers increased their understanding of evolution. In 1843 homology was a term that was used for organs that were similar in different animals, this meant that the organ just had to be present regardless of the function (Haszprunar 1992). In 1982 the definition of homology was changed meaning the same as apomorphy; in other words, a trait that has developed between two species that was not present in the ancestor (Haszprunar 1992). Both of these definitions have a role in shaping the classical since of the definition of homology which stated by Herron and Freeman (2014) as similarity of structures regardless of the function.
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There are various computer programs that can aid in sequencing these segments of DNA and generate phylogenetic trees. The programs are specifically looking for intron indels, retroposon, gene duplications and linked genes (Rokas and Holland 2000). Researchers can use several supermatrix formations that have already been created to pair up species (Gatesy et al. 2012). In our example, DNA was extracted, purified and then sequences. The computer program was looking for the presence or absence of transposon sites when compared to one of the supermatrix formations(Gatesy et al. 2012). Additionally, as the computer program runs the sequences gathered from the whale and hippopotamus the sequences will align allowing for additional differences and similarities in the genetic code to be found. After the genetic code has been sequenced, the computer programs can run programs to make phyogenetic …show more content…
Bootstraping is a term that is used to describe a process in which you use the original DNA segment to recreate a body of randomly pulled sequences, which can then be compared with the original group. Bootstraping is important because it injects a percentage of credibility to your phylogenetic tree. Once a phylogenetic tree is determined to be the most likely, bootstrap numbers are added to show the level of confidence that the branches are probable. These bootstrap numbers are recorded to the top of the branches of the phylogenetic trees. The higher the numbers the more probable the tree is correct. The general rule given is the closer to 100 the number is, the more certain you can be about the relationship. Several researchers state that there is a strong (90-100) bootstrap number for the notion that whales and hippopotamus are related (Gatesy et al.
For the original analysis, the corrected pairwise distance will be calculated using the Jukes–Cantor and the Maximum Composite Likelihood Model. The Jukes–Cantor model assumes that the rate of nucleotide substitution or all nucleotides (C, A, T and G) are equal, that nucleotide frequencies are equal, that there is an equal rate of substitution among sites, and does not correct for the lower rate of transversion substitutes in comparison to transitional substitutions (Jukes and Cantor, 1969). The Maximum Composite Likelihood takes into account the phylogenic relationship between sequences, using the sum of the log likelihoods of the bases as the composite likelihood. Both pair wise distances and substitution parameters are estimated using the Maximum Composite Likelihood (Tamura et al. 2004). Both models should yield different maximum sequence divergence and average divergence that can then be compared to the original paper. With sequence divergence data, the temporal origin of the genus can be identified. The two alternate models to the Kimura-2 parameter will be analyzed to discuss which methods yield results closest to the expected time origin of the genus
Rienzo, Anna Di. Wilson, Allan. 1991. Branching pattern in the evolutionary tree for human mitochondrial DNA. Evolution 88: 1597-1601.
New technologies and advancement in the area of field research has allowed biologist and primatologist to analyze information more effectively and efficiently. Through the non-invasive collection of fecal samples, researchers are able to extract and analyze DNA to help determine individual attribute, as well as population dynamics. In addition to DNA, fecal samples also contain hormones and parasites that help in determining the overall health of the depositor (Newton-Fisher NE, 2010). Other technologies include the use of Geographic Information Systems allows for mapping the ranges of chimpanzees, and satellite imagery is used to view the deforestation of select areas (Goodall, 2002).
Scientists had some idea to the evolutionary process of whales. “It has always been clear that aquatic cetaceans must have evolved from terrestrial mammals and returned to the water, and the forelimbs of recent cetaceans still have the same general pattern as that of land mammals.” (Walking with Whales) It was known fact that land mammals and whales were related. However, the change from ancient whales to modern whales is drastic.
Shubin, N.H, Tabin, C., & Caroll, S. 2009. Deep homology and the origins of evolutionary novelty. Nature, 457: 818-823.
Scientists have gathered the evidence for evolutionary change, but the evidence appears to light by means of fossils (paleontology) and the rock record (ge...
In 2000, Dr. Philip D. Gingerich, a paleontologist from the University of Michigan, and his associates discovered two primitive whale fossils in the Balochistan Province of Pakistan. By dating the limestone located in the Habib Rahi Formation of the Balochistan Province, Gingerich estimated these fossils to be about 47 million years old. According to author David Braun of National Geographic News, “The researchers have classified one, Rodhocetus balochistanensis, as a new species of an existing genus, and the other, Artiocetus clavis, as a new species and new genus” (Braun, 5). The discovery of these two fossils suggests that the closest living relative of these primitive whales could possibly be the modern day hippopotamus. This suggested relationship is based on similarities in the bone structure between the two animals.
Evolution is the processes in which different types of organisms developed and diversified from earlier forms on earth.Scientists use fouls and data to support the evolution and its theory.These fouls help scientists see the development of organisms throughout the years.They also use the fouls to see when land was in merian life and when it moved to land.The purpose of the this lab was to see the development of organisms and to compare the skulls.We were able to see that the organisms with similar names had similar resemblance to the others with the about the same names.
This theory was developed from the combined efforts of many different researchers. Together, Konstantin Mereschkowsky, Boris Mikhaylovich Kozo-Polyansky, Ivan Wallin, and Lynn Margulis are the main researchers whom coined the term “symbiogenesis” referring to the long term, or permanent physical association between “differently named partners” (taxa), or the genesis of new species through the merging of two or more existing species (Margulis). Endosymbiosis and symbiogenesis define hypothetical theories thought to justify the origin of species in addition to the processes of natural selection and random mutation. B.M. Kozo-Polyansky and Lynn Margulis, who very much admired Kozo-Polyansky’s work, both believed symbiogenesis was the major source of innovation for evolution (Margulis). The most well known of the first speculations about the origin of organelles, was Mereschkowsky. He primarily studied the chloroplast and was the first to suggest they were obtained initially from unicellular organisms that had been “enslaved” as endosymbionts. However, his theory was turned ...
... tested hairs and other parts for DNA and concluded that they fit into our family tree. “ Those hair samples that could not be identified as known animal or human were subsequently screened using DNA testing, beginning with sequencing of mitochondrial DNA followed by sequencing nuclear DNA to determine where these individuals fit in the tree of life” (Ketchum 2013).
DNA has to be in a perfect sequence. Finding mammals, amphibians, and even reptilians to fit in the gap was a far stretch. Looking for relatives of dinosaurs was the better game. In the end, rainforest tree frogs, a few selected birds, and an unnamed reptilian was the closest to the dinosaur’s genetic code. However, the small amount of DNA obtained from the amber would not be enough to find the genetic code. To fix the problem, scientists multiplied the DNA through the use of the Polymerase chain reaction (a tool that produces thousands of genetic codes through the DNA put into the device). From there, the genetic code was known as A,T,C,G. Scientists then used computers to find the overlapping regions and set out the specific genetic code. The leading geneticist, Henry Wu, was the man attributed with the fame of completing the
He realized that snake embryos had bumps where there should be legs. Which mean they probably evolved from a creature with legs. He noticed that whale embryos had teeth, but adult whales did not have teeth. The most shocking of his embryotic studies involved human embryos. He noted that the human embryos as slits around the neck, the same in fish. The difference is that in fish the develop into gills, and in human the become the bones of the inner ear. This showed that humans must be descended from fish. This led him to the conclusion that all species were somehow connected. He theorized that beginning with a common ancestor, species had changed dramatically over generations. Some species may add new body features, or lose them. He called this descent with
Phylogeny is an estimated representation of an organism’s or group of organisms’ evolutionary history. Scientist use a phylogenetic tree to visualize ancestor descent relationship through time. The closer together different taxa are represented in a phylogenetic tree the more closely related the species are to each other. Phylogenetic tree is consists of different types of characteristics which makes it easier for scientists to understand them. One of the characteristic is a branch, which represent the population of specie through the beginning of time. Another characteristic is a terminal node (or the tip of the branch), which represent the most recent species. The last characteristic is a node which is where 2 branches diverged, this represents speciation where the ancestral species split from one specie to two. Speciation is when one organism or one population diverging and can’t interbreed any more. Phylogenetic and phylogenetic trees require speciation to have occurred.
It is easy to say that species are constantly changing, and branching off into totally new species. But how do we know where the species originate? Phylogenies help to show us how all kinds of species are related to each other, and why. These relationships are put into what can be called a cladogram, which links species to common ancestors, in turn showing where, when, how, and why these ancestors diverged to form new species. Without phylogenies, it would be extremely difficult to put species in specific categories or relate them to one another. Along with phylogenies can come conflict on which species should be related to one another. This conflict causes many hypotheses and experiments, which can lead to phylogenetic retrofitting, which means adding some kind of data to a phylogeny that was not originally included. In M. S. Y. Lee’s article “Turtle origins: insights from phylogenetic retrofitting and molecular scaffolds”, the origin of the turtle (Testudines) is very controversial, and has been the source of experimenting to try to prove whether it should be placed under anapsid-grade parareptiles, according to Bayesian analyses, or diapsids as sisters to living archosaurs. The use of experiments including molecular scaffolding, which is an experiment involving using the scaffold protein of the backbone to place the turtles in a certain taxa, is used to show where turtles should actually be placed. I find it very interesting that scientists continue to go back and forth between new and old phylogenies, constantly rearranging and questioning the placement. Phylogenies are not just important for showcasing where species originated from, but also to illustrate how DNA sequences evolve as well. For example, in class, we t...
The fossil record is evidence of evolution. Fossils are often fingerprints of evolution. They help scientists track how species evolved over millions of years (2010). Historical biogeography is responsible for determining the geographical origin of a species and history (Guiterrez-Garcia, 2010). They often trace the origin of a new species due to an isolation in geography or the movement to a new location, and evolved into a new distinct species. Comparative anatomy began even before the theory of evolution. Scientists researched how species were similar, organ systems developed, and limbs evolved (Abdala, 2010). This can help scientists start to understand how or why a species separated. Comparative anatomy is scientific proof of evolution. Embryology is similar to comparative anatomy. Embryology studies the similarities among embryos (Hall, 2010). Animal embryo cells develop similarly regardless of species until certain point when differences begin to develop. These markers are evolutionary evidence for when species began to separate. Molecular biology uses the analysis of RNA and DNA to mark the evolution of a species ...