Then zoom out even farther to include many more individuals (say, from multiple meadows in the same region) and more generations. Next, imagine taking your pedigree and getting rid of the organisms, thus keeping only the descent relationships, which are the glue that holds the population together (Figure 1D inset box). Note that each individual in the figure has two parents, but each gives rise to a variable number of offspring in the next generation. A pedigree for this population might look something like the one in Figure 1C. Now, expand your image to encompass all the butterflies of this species in a particular meadow over several generations. If you focus on four individual butterflies in both the parental and offspring generations, the resulting pedigree may appear like the one in Figure 1B. To better understand what a phylogeny represents, start by imagining one generation of butterflies of a particular species living the same area and producing offspring.
A more complete view of this subject can be developed by learning about how traits evolve along trees, how trees are reconstructed, and how trees are used to study various aspects of evolution. This understanding allows present-day researchers to use phylogenies to visualize evolution, organize their knowledge of biodiversity, and structure and guide ongoing evolutionary research.īut what exactly is a phylogeny? Moreover, how should one read and interpret one of these diagrams? In an attempt to answer such questions, the following sections present a brief introduction to tree thinking. This may be the reason why biologists have only in the last few decades come to develop a rigorous understanding of phylogenetic trees. However, it turns out that the tree model of evolution is somewhat counterintuitive and easily misunderstood. Therefore, one might assume that, by now, most scientists would be exceedingly comfortable with "tree thinking"-reading and interpreting phylogenies. Tree diagrams have been used in evolutionary biology since the time of Charles Darwin. Furthermore, because these trees show descent from a common ancestor, and because much of the strongest evidence for evolution comes in the form of common ancestry, one must understand phylogenies in order to fully appreciate the overwhelming evidence supporting the theory of evolution. Phylogenies are useful for organizing knowledge of biological diversity, for structuring classifications, and for providing insight into events that occurred during evolution. 2020 doi:10.1001/ phylogenetic tree, also known as a phylogeny, is a diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor. Preventive Services Task Force recommendation statement.
Screening for hepatitis C virus infection in adolescents and adults: U.S. National Institute of Diabetes and Digestive and Kidney Diseases. Definition and facts of liver transplant.Epidemiology and transmission of hepatitis C virus infection. Clinical manifestations and natural history of chronic hepatitis C virus infection. The revolution in treatment of hepatitis C. Centers for Disease Control and Prevention. Hepatitis C questions and answers for health professionals.Acute hepatitis C also responds well to antiviral therapy. In studies of people diagnosed with acute HCV, rates of spontaneous viral clearance have varied from 15% to 25%. Some people clear HCV from their bodies after the acute phase, an outcome known as spontaneous viral clearance. Acute symptoms appear one to three months after exposure to the virus and last two weeks to three months.Īcute hepatitis C infection doesn't always become chronic. When signs and symptoms are present, they may include jaundice, along with fatigue, nausea, fever and muscle aches. Acute hepatitis C usually goes undiagnosed because it rarely causes symptoms.
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Chronic hepatitis C is usually a "silent" infection for many years, until the virus damages the liver enough to cause the signs and symptoms of liver disease. Long-term infection with the hepatitis C virus is known as chronic hepatitis C.
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