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The Academy's Evolution Site Biological evolution is one of the most fundamental concepts in biology. The Academies have been for a long time involved in helping those interested in science comprehend the theory of evolution and how it influences all areas of scientific exploration. This site provides a wide range of tools for students, teachers, and general readers on evolution. It has important video clips from NOVA and WGBH's science programs on DVD. Tree of Life The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is used in many religions and cultures as symbolizing unity and love. It has many practical applications as well, such as providing a framework to understand the evolution of species and how they respond to changing environmental conditions. The first attempts to depict the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on the sampling of different parts of living organisms, or sequences of short fragments of their DNA greatly increased the variety of organisms that could be included in a tree of life2. These trees are mostly populated by eukaryotes, and bacterial diversity is vastly underrepresented3,4. By avoiding the need for direct observation and experimentation, genetic techniques have enabled us to depict the Tree of Life in a much more accurate way. Particularly, molecular methods allow us to construct trees using sequenced markers such as the small subunit ribosomal gene. Despite the rapid growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly true of microorganisms that are difficult to cultivate and are often only found in a single sample5. A recent analysis of all genomes that are known has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that are not isolated and which are not well understood. This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if specific habitats need special protection. This information can be utilized in a variety of ways, including finding new drugs, fighting diseases and improving the quality of crops. It is also useful in conservation efforts. It helps biologists discover areas that are most likely to have cryptic species, which may have important metabolic functions, and could be susceptible to changes caused by humans. While funding to protect biodiversity are important, the most effective method to preserve the world's biodiversity is to empower the people of developing nations with the information they require to act locally and support conservation. Phylogeny A phylogeny is also known as an evolutionary tree, reveals the relationships between various groups of organisms. Utilizing molecular data similarities and differences in morphology or ontogeny (the course of development of an organism) scientists can create an phylogenetic tree that demonstrates the evolution of taxonomic categories. Phylogeny is essential in understanding biodiversity, evolution and genetics. A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms with similar traits and have evolved from an ancestor with common traits. These shared traits can be either analogous or homologous. Homologous traits are similar in their evolutionary origins while analogous traits appear like they do, but don't have the same ancestors. Scientists arrange similar traits into a grouping known as a the clade. All organisms in a group have a common trait, such as amniotic egg production. They all evolved from an ancestor that had these eggs. Read More Listed here is constructed by connecting clades to identify the organisms which are the closest to one another. For a more precise and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships among organisms. This data is more precise than morphological data and provides evidence of the evolution history of an individual or group. The analysis of molecular data can help researchers determine the number of organisms who share the same ancestor and estimate their evolutionary age. The phylogenetic relationship can be affected by a number of factors that include the phenotypic plasticity. This is a type of behavior that alters as a result of specific environmental conditions. This can cause a trait to appear more similar to one species than another and obscure the phylogenetic signals. This problem can be addressed by using cladistics, which is a a combination of homologous and analogous traits in the tree. Furthermore, phylogenetics may aid in predicting the time and pace of speciation. This information can aid conservation biologists in making decisions about which species to save from extinction. In the end, it is the conservation of phylogenetic variety that will result in an ecosystem that is balanced and complete. Evolutionary Theory The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would evolve according to its own needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can cause changes that are passed on to the next generation. In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance—came together to form the current evolutionary theory which explains how evolution happens through the variation of genes within a population, and how those variations change in time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is the foundation of current evolutionary biology, and can be mathematically described. Recent discoveries in the field of evolutionary developmental biology have shown that variations can be introduced into a species by mutation, genetic drift, and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution, which is defined by changes in the genome of the species over time, and also the change in phenotype as time passes (the expression of the genotype in an individual). Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking throughout all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence that supports evolution increased students' understanding of evolution in a college-level biology course. To find out more about how to teach about evolution, please read The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education. Evolution in Action Scientists have traditionally studied evolution through looking back in the past, analyzing fossils and comparing species. They also study living organisms. Evolution isn't a flims event, but an ongoing process. The virus reinvents itself to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior in the wake of the changing environment. The changes that result are often evident. However, it wasn't until late 1980s that biologists realized that natural selection could be seen in action, as well. The key is that different traits confer different rates of survival and reproduction (differential fitness) and are passed from one generation to the next. In the past, if one particular allele—the genetic sequence that controls coloration – was present in a population of interbreeding organisms, it could quickly become more prevalent than all other alleles. As time passes, that could 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. Observing evolutionary change in action is easier when a particular species has a rapid generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from one strain. The samples of each population were taken regularly, and more than 50,000 generations of E.coli have passed. Lenski's work has shown that mutations can alter the rate of change and the efficiency of a population's reproduction. It also proves that evolution is slow-moving, a fact that many are unable to accept. Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. 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 growing awareness of its significance, especially in a world which is largely shaped by human activities. This includes the effects of climate change, pollution and habitat loss, which prevents many species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.