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The Academy's Evolution Site Biological evolution is one of the most fundamental concepts in biology. The Academies are committed to helping those who are interested in the sciences learn about the theory of evolution and how it can be applied in all areas of scientific research. This site provides teachers, students and general readers with a variety of learning resources about evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD. Tree of Life The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It appears in many religions and cultures as a symbol of unity and love. It can be used in many practical ways in addition to providing a framework for understanding the history of species and how they respond to changes in environmental conditions. Early attempts to represent the world of biology were founded on categorizing organisms on their physical and metabolic characteristics. These methods, which depend on the collection of various parts of organisms or short DNA fragments, have significantly increased the diversity of a Tree of Life2. These trees are largely composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4. Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods enable us to create trees by using sequenced markers, such as the small subunit of ribosomal RNA gene. Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are often only found in a single sample5. 에볼루션 무료체험 of all genomes that are known has created a rough draft of the Tree of Life, including many bacteria and archaea that are not isolated and their diversity is not fully understood6. This expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if particular habitats require special protection. This information can be used in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. This information is also extremely useful in conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species with important metabolic functions that could be at risk from anthropogenic change. Although funds to protect biodiversity are essential, ultimately the best way to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within. Phylogeny A phylogeny (also known as an evolutionary tree) illustrates the relationship between species. Scientists can build a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic groups using molecular data and morphological differences or similarities. Phylogeny is essential in understanding biodiversity, evolution and genetics. A basic phylogenetic Tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestors. These shared traits can be analogous or homologous. Homologous characteristics are identical in their evolutionary path. Analogous traits might appear like they are however they do not share the same origins. Scientists group similar traits into a grouping referred to as a clade. For example, all of the organisms in a clade share the characteristic of having amniotic egg and evolved from a common ancestor that had these eggs. The clades are then connected to form a phylogenetic branch to identify organisms that have the closest connection to each other. Scientists use DNA or RNA molecular information to build a phylogenetic chart that is more accurate and precise. This information is more precise and provides evidence of the evolution history of an organism. Molecular data allows researchers to determine the number of organisms that share a common ancestor and to estimate their evolutionary age. The phylogenetic relationships between organisms can be affected by a variety of factors, including phenotypic plasticity a kind of behavior that alters in response to specific environmental conditions. This can cause a particular trait to appear more similar in one species than another, clouding the phylogenetic signal. However, this problem can be reduced by the use of techniques like cladistics, which combine analogous and homologous features into the tree. Additionally, phylogenetics can help predict the length and speed of speciation. This information can assist conservation biologists in making decisions about which species to save from extinction. In the end, it's the conservation of phylogenetic variety which will create an ecosystem that is balanced and complete. Evolutionary Theory The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could develop according to its own needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of traits can cause changes that are passed on to the next generation. In the 1930s & 1940s, theories from various fields, such as natural selection, genetics & particulate inheritance, were brought together to form a modern evolutionary theory. This describes how evolution occurs by the variation in genes within the population and how these variants alter over time due to natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically described. Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species via mutation, genetic drift and reshuffling of genes in sexual reproduction, and also through the movement of populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of a genotype over time), can lead to evolution, which is defined by changes in the genome of the species over time and also by changes in phenotype over time (the expression of the genotype in the individual). Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking in all aspects of biology. In a recent study conducted by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution in an undergraduate biology course. To learn more about how to teach about evolution, read The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education. Evolution in Action Traditionally, scientists have studied evolution through studying fossils, comparing species and observing living organisms. However, evolution isn't something that happened in the past, it's an ongoing process happening today. Bacteria evolve and resist antibiotics, viruses evolve and elude new medications and animals alter their behavior in response to a changing planet. The changes that result are often evident. It wasn't until the late 1980s when biologists began to realize that natural selection was also in play. The reason is that different characteristics result in different rates of survival and reproduction (differential fitness) and can be passed from one generation to the next. In the past, if an allele – the genetic sequence that determines colour – appeared in a population of organisms that interbred, it might become more prevalent than any other allele. In time, this could mean the number of black moths within a particular population could rise. The same is true for many other characteristics—including morphology and behavior—that vary among populations of organisms. The ability to observe evolutionary change is easier when a species has a rapid turnover of its generation such as bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each are taken every day and over 50,000 generations have now passed. Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency at which a population reproduces. It also shows that evolution takes time, a fact that some people find difficult to accept. Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more common in populations that have used insecticides. This is due to the fact that the use of pesticides creates a pressure that favors individuals who have resistant genotypes. The rapidity of evolution has led to a greater appreciation of its importance particularly in a world shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss, which prevents many species from adapting. Understanding evolution can help us make better decisions about the future of our planet as well as the life of its inhabitants.