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The Academy's Evolution Site The concept of biological evolution is among the most central concepts in biology. The Academies are involved in helping those who are interested in science to comprehend the evolution theory and how it is incorporated across all areas of scientific research. This site provides students, teachers and general readers with a variety of learning resources on evolution. It includes key video clips from NOVA and the WGBH-produced science programs on DVD. Tree of Life The Tree of Life is an ancient symbol of the interconnectedness of all life. It is an emblem of love and unity in many cultures. 에볼루션 바카라 체험 has practical uses, like providing a framework for understanding the evolution of species and how they respond to changes in environmental conditions. Early approaches to depicting the biological world focused on separating organisms into distinct categories which had been distinguished by their physical and metabolic characteristics1. These methods, which relied on the sampling of different parts of living organisms or on short fragments of their DNA greatly increased the variety of organisms that could be represented in the tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity is still largely unrepresented3,4. Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. We can construct trees using molecular methods such as the small subunit ribosomal gene. Despite the dramatic growth of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are typically only present in a single specimen5. A recent analysis of all genomes known to date has produced a rough draft of the Tree of Life, including a large number of archaea and bacteria that have not been isolated, and their diversity is not fully understood6. The expanded Tree of Life can be used to assess the biodiversity of a specific region and determine if particular habitats require special protection. This information can be used in a range of ways, from identifying the most effective remedies to fight diseases to enhancing crop yields. The information is also incredibly beneficial in conservation efforts. It can help biologists identify the areas most likely to contain cryptic species with potentially important metabolic functions that may be vulnerable to anthropogenic change. While funds to protect biodiversity are important, the most effective way to conserve the biodiversity of the world is to equip more people in developing nations with the knowledge they need to act locally and support conservation. Phylogeny A phylogeny (also called an evolutionary tree) depicts the relationships between species. By using molecular information, morphological similarities and differences, or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. Phylogeny is essential in understanding the evolution of biodiversity, evolution and genetics. A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms with similar traits and have evolved from a common ancestor. These shared traits could be either analogous or homologous. Homologous characteristics are identical in their evolutionary journey. Analogous traits might appear similar however they do not have the same ancestry. Scientists group similar traits into a grouping referred to as a Clade. All organisms in a group share a characteristic, like amniotic egg production. They all derived from an ancestor with these eggs. A phylogenetic tree is built by connecting the clades to identify the species who are the closest to each other. For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships between organisms. This information is more precise and provides evidence of the evolutionary history of an organism. The use of molecular data lets researchers determine the number of organisms that have the same ancestor and estimate their evolutionary age. Phylogenetic relationships can be affected by a number of factors, including the phenomenon of phenotypicplasticity. This is a kind of behavior that changes as a result of particular environmental conditions. This can make a trait appear more similar to one species than to the other which can obscure the phylogenetic signal. However, this issue can be reduced by the use of methods such as cladistics which combine similar and homologous traits into the tree. Additionally, phylogenetics can help determine the duration and rate at which speciation takes place. This information will assist conservation biologists in making choices about which species to protect from the threat of extinction. In the end, it is the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete. Evolutionary Theory The main idea behind evolution is that organisms acquire different features over time due to their interactions with their environments. A variety of theories about evolution have been developed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that could be passed on to the offspring. In the 1930s and 1940s, ideas from different fields, including natural selection, genetics & particulate inheritance, merged to form a modern synthesis of evolution theory. This explains how evolution happens through the variations in genes within a population and how these variations change with time due to natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained. Recent discoveries in evolutionary developmental biology have shown the ways in which variation can be introduced to a species via genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with others such as directional selection and gene erosion (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time, as well as changes in the phenotype (the expression of genotypes in individuals). Students can better understand the concept of phylogeny through incorporating evolutionary thinking in all areas of biology. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution helped students accept the concept of evolution in a college biology course. For more details on how to teach evolution, see The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education. Evolution in Action Traditionally scientists have studied evolution through looking back—analyzing fossils, comparing species and observing living organisms. But evolution isn't a thing that occurred in the past; it's an ongoing process that is taking place right now. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The resulting changes are often easy to see. It wasn't until the late 1980s when biologists began to realize that natural selection was also at work. The key to this is that different traits result in an individual rate of survival as well as reproduction, and may be passed down from one generation to the next. In the past, if an allele – the genetic sequence that determines colour was present in a population of organisms that interbred, it might become more common than other allele. Over time, that would mean that the number of black moths within the population could increase. The same is true for many other characteristics—including morphology and behavior—that vary among populations of organisms. It is easier to see evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from one strain. Samples of each population have been taken regularly and more than 500.000 generations of E.coli have passed. Lenski's work has demonstrated that a mutation can profoundly alter the rate at which a population reproduces—and so, the rate at which it evolves. It also proves that evolution takes time, a fact that some people find hard to accept. Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more common in populations that have used insecticides. This is because pesticides cause an exclusive pressure that favors individuals who have resistant genotypes. The rapidity of evolution has led to a greater awareness of its significance especially in a planet shaped largely by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution will help us make better choices about the future of our planet as well as the lives of its inhabitants.