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The Academy's Evolution Site The concept of biological evolution is a fundamental 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 affects all areas of scientific exploration. This site provides teachers, students and general readers with a variety of educational resources on evolution. It contains important video clips from NOVA and WGBH-produced science programs on DVD. Tree of Life The Tree of Life is an ancient symbol that represents the interconnectedness of all life. It is used in many religions and cultures as an emblem of unity and love. It has numerous practical applications as well, including providing a framework to understand the evolution of species and how they respond to changes in environmental conditions. The first attempts to depict the world of biology were founded on categorizing organisms on their physical and metabolic characteristics. These methods, based on the sampling of different parts of living organisms or sequences of short DNA fragments, significantly expanded the diversity that could be included in the tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is not represented in a large way3,4. In avoiding the necessity of direct observation and experimentation, genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. We can construct trees by 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 awaits discovery. This is especially true of microorganisms, which are difficult to cultivate and are often only found in a single sample5. A recent analysis of all known genomes has created a rough draft of the Tree of Life, including a large number of archaea and bacteria that are not isolated and which are not well understood. This expanded Tree of Life can be used to assess the biodiversity of a particular area and determine if certain habitats need special protection. This information can be used in many ways, including finding new drugs, battling diseases and improving the quality of crops. It is also beneficial to conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species that could have important metabolic functions that may be at risk of anthropogenic changes. Although funding to protect biodiversity are crucial, ultimately the best way to preserve the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to act locally in order to promote conservation from within. Phylogeny A phylogeny (also called an evolutionary tree) illustrates the relationship between different organisms. Scientists can create an phylogenetic chart which shows the evolutionary relationships between taxonomic groups using molecular data and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution. A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits can be either homologous or analogous. Homologous traits are the same in their evolutionary path. Analogous traits might appear similar, but they do not have the same ancestry. Scientists group similar traits into a grouping known as a the 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 which had these eggs. The clades are then connected to form a phylogenetic branch to identify organisms that have the closest relationship to. For a more precise and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to identify the relationships between organisms. This data is more precise than morphological information and gives evidence of the evolutionary history of an individual or group. Researchers can use Molecular Data to determine the age of evolution of living organisms and discover how many species have a common ancestor. Phylogenetic relationships can be affected by a variety of factors that include phenotypicplasticity. This is a type behavior that alters as a result of particular environmental conditions. This can cause a trait to appear more resembling to one species than another which can obscure the phylogenetic signal. However, this issue can be reduced by the use of methods such as cladistics that include a mix of analogous and homologous features into the tree. Additionally, phylogenetics can aid in predicting the length and speed of speciation. This information can assist conservation biologists decide which species to protect from extinction. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced. Evolutionary Theory The fundamental concept of evolution is that organisms develop various characteristics over time as a result of their interactions with their surroundings. Many theories of evolution have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits can cause changes that could be passed onto offspring. In the 1930s and 1940s, concepts from a variety of fields — including genetics, natural selection and particulate inheritance—came together to form the modern synthesis of evolutionary theory that explains how evolution occurs through the variation of genes within a population, and how these variants change over time as a result of natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically described. Recent advances in the field of evolutionary developmental biology have shown how variation can be introduced to a species through mutations, genetic drift and reshuffling of genes during sexual reproduction and migration between populations. These processes, in conjunction with other ones like directionally-selected selection and erosion of genes (changes in the 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 aspects of biology. 에볼루션게이밍 conducted by Grunspan and colleagues, for instance revealed that teaching students about the evidence for evolution helped students accept the concept of evolution in a college-level biology course. For more information on how to teach evolution, see The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education. Evolution in Action Traditionally, scientists have studied evolution by studying fossils, comparing species, and observing living organisms. But evolution isn't just something that happened in the past; it's an ongoing process taking place today. Viruses evolve to stay away from new medications and bacteria mutate to resist antibiotics. Animals alter their behavior as a result of a changing world. The resulting changes are often evident. It wasn't until late 1980s that biologists began realize that natural selection was also at work. The main reason is that different traits confer a different rate of survival as well as reproduction, and may be passed on from one generation to another. In the past, if 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 in a population may increase. 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 generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples of each population have been collected frequently and more than 50,000 generations of E.coli have been observed to have passed. Lenski's research has shown that a mutation can dramatically alter the rate at the rate at which a population reproduces, and consequently the rate at which it changes. It also demonstrates that evolution takes time, something that is hard for some to accept. Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. 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 world that is largely shaped by human activity. This includes pollution, climate change, and habitat loss, which prevents many species from adapting. Understanding evolution can help us make better choices about the future of our planet as well as the lives of its inhabitants.