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The Academy's Evolution Site Biology is a key concept in biology. The Academies have been for a long time involved in helping those interested in science understand the concept of evolution and how it influences every area of scientific inquiry. This site provides students, teachers and general readers with a range of learning resources on evolution. It contains key video clips from NOVA and the WGBH-produced science programs on DVD. Tree of Life The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is an emblem of love and unity across many cultures. It has numerous practical applications as well, including providing a framework to understand the history of species and how they respond to changes in environmental conditions. The first attempts to depict the world of biology were built on categorizing organisms based on their metabolic and physical characteristics. These methods, which relied on the sampling of different parts of living organisms or on sequences of small fragments of their DNA greatly increased the variety of organisms that could be included in the tree of life2. The trees are mostly composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4. Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed using molecular techniques, such as the small-subunit ribosomal gene. ???? ?? of Life has been significantly expanded by genome sequencing. However there is still a lot of diversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are typically only present in a single sample5. A recent analysis of all known genomes has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated and which are not well understood. This expanded Tree of Life can be used to determine the diversity of a specific region and determine if certain habitats need special protection. The information is useful in many ways, including finding new drugs, fighting diseases and improving the quality of crops. This information is also valuable to conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. Although funding to protect biodiversity are crucial however, the most effective method to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within. Phylogeny A phylogeny is also known as an evolutionary tree, shows the relationships between different groups of organisms. Scientists can create a phylogenetic chart that shows the evolution of taxonomic categories using molecular information and morphological similarities or differences. The role of phylogeny is crucial in understanding genetics, biodiversity and evolution. A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestors. These shared traits could be analogous or homologous. Homologous traits are similar in their evolutionary origins and analogous traits appear like they do, but don't have the same ancestors. Scientists combine similar traits into a grouping called a Clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs. They evolved from a common ancestor who had these eggs. The clades then join to create a phylogenetic tree to determine the organisms with the closest connection to each other. For a more precise and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to establish the relationships among organisms. This information is more precise and provides evidence of the evolution of an organism. The analysis of molecular data can help researchers identify the number of organisms who share a common ancestor and to estimate their evolutionary age. The phylogenetic relationships of organisms can be affected by a variety of factors including phenotypic plasticity, a kind of behavior that changes in response to specific environmental conditions. This can cause a trait to appear more similar to a species than to the other, obscuring the phylogenetic signals. However, this issue can be cured by the use of methods like cladistics, which combine similar and homologous traits into the tree. Additionally, phylogenetics can help determine the duration and speed at which speciation occurs. This information can assist conservation biologists in making choices about which species to safeguard from the threat of extinction. Ultimately, it is the preservation of phylogenetic diversity that will create an ecologically balanced and complete ecosystem. Evolutionary Theory The central theme in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have come up with theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that a living thing would evolve according to its individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy and Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that can be passed on to future generations. In the 1930s and 1940s, theories from a variety of fields -- including genetics, natural selection, and particulate inheritance - came together to form the current evolutionary theory, which defines how evolution occurs through the variation of genes within a population and how those variants change in time due to natural selection. This model, which is known as genetic drift, mutation, gene flow, and sexual selection, is a cornerstone of modern evolutionary biology and is mathematically described. Recent discoveries in the field of evolutionary developmental biology have revealed the ways in which variation can be introduced to a species via mutations, genetic drift, reshuffling genes during 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 phenotype (the expression of genotypes in individuals). Students can better understand phylogeny by incorporating evolutionary thinking into all areas of biology. In a recent study conducted by Grunspan and colleagues. It was found that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. For more information on how to teach about evolution, please look up The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education. Evolution in Action Traditionally scientists have studied evolution through studying fossils, comparing species and observing living organisms. Evolution isn't a flims event; it is a process that continues today. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior because of a changing environment. The changes that result are often easy to see. It wasn't until late 1980s that biologists began realize that natural selection was at work. The key is that various characteristics result in different rates of survival and reproduction (differential fitness) and can be transferred from one generation to the next. In the past, when one particular allele--the genetic sequence that defines color in a population of interbreeding organisms, it might quickly become more common than the other alleles. In time, this could mean that the number of moths with black pigmentation may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms. Observing evolutionary change in action is easier when a species has a fast generation turnover such as bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain. samples of each population are taken on a regular basis and more than 500.000 generations have passed. Lenski's work has demonstrated that a mutation can profoundly alter the speed at which a population reproduces--and so the rate at which it evolves. It also shows evolution takes time, a fact that is difficult for some to accept. Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides have been used. This is because pesticides cause an exclusive pressure that favors those who have resistant genotypes. The rapidity of evolution has led to an increasing recognition of its importance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding ???? ??? can aid you in making better decisions regarding the future of the planet and its inhabitants.
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