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The Academy's Evolution Site Biology is one of the most fundamental concepts in biology. The Academies have been active for a long time in helping people who are interested in science understand the theory of evolution and how it influences every area of scientific inquiry. This site provides students, teachers and general readers with a range of educational resources on evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD. Tree of Life The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It is a symbol of love and unity in many cultures. It also has practical applications, like providing a framework to understand the evolution of species and how they react to changes in environmental conditions. The earliest attempts to depict the world of biology focused on separating organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods rely on the collection of various parts of organisms or short DNA fragments have significantly increased the diversity of a tree of Life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4. In avoiding the necessity of direct observation and experimentation, genetic techniques have made it possible to depict the Tree of Life in a more precise way. We can create trees using molecular techniques like the small-subunit ribosomal gene. The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much biodiversity to be discovered. This is particularly the case for microorganisms which are difficult to cultivate and are typically found in one sample5. A recent study of all known genomes has produced a rough draft version of the Tree of Life, including a large number of bacteria and archaea that are not isolated and their diversity is not fully understood6. This expanded Tree of Life can be used to evaluate the biodiversity of a particular area and determine if certain habitats require special protection. This information can be utilized in a variety of ways, including identifying new drugs, combating diseases and enhancing crops. This information is also extremely beneficial to conservation efforts. It can help biologists identify areas most likely to be home to cryptic species, which may perform important metabolic functions and be vulnerable to the effects of human activity. While conservation funds are essential, the best method to protect the world's biodiversity is to equip more people in developing nations with the necessary knowledge to act locally and support conservation. Phylogeny A phylogeny (also called an evolutionary tree) depicts the relationships between organisms. Scientists can build a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic categories using molecular information and morphological similarities or differences. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution. A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that have evolved from common ancestral. These shared traits are either analogous or homologous. Homologous traits are similar in their evolutionary origins and analogous traits appear similar but do not have the identical origins. Scientists group similar traits together into a grouping called a the clade. For instance, all of the species in a clade share the trait of having amniotic egg and evolved from a common ancestor which had eggs. A phylogenetic tree is built by connecting the clades to identify the species which are the closest to each other. Scientists utilize DNA or RNA molecular information to construct a phylogenetic graph 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 identify the number of species who share the same ancestor and estimate their evolutionary age. The phylogenetic relationships between species can be affected by a variety of factors including phenotypic plasticity, an aspect of behavior that alters in response to specific environmental conditions. This can cause a particular trait to appear more similar to one species than another, clouding the phylogenetic signal. However, this issue can be cured by the use of methods such as cladistics which include a mix of homologous and analogous features into the tree. In addition, phylogenetics can help predict the duration and rate of speciation. This information can assist conservation biologists make decisions about which species to protect from extinction. In talks about it , it's the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced. Evolutionary Theory The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. Several theories of evolutionary change have been proposed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed on to the offspring. In the 1930s and 1940s, ideas from a variety of fields—including natural selection, genetics, and particulate inheritance – came together to create the modern evolutionary theory synthesis that explains how evolution is triggered by the variation of genes within a population and how those variants change in time due to natural selection. This model, known as genetic drift, mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and is mathematically described. Recent developments in evolutionary developmental biology have demonstrated how variations can be introduced to a species through mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, along with others such as directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time as well as changes in the phenotype (the expression of genotypes in an individual). Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. In a recent study conducted by Grunspan and co. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during a college-level course in biology. For more information on how to teach about evolution, look up 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 by looking back, studying fossils, comparing species, and studying living organisms. However, evolution isn't something that occurred in the past, it's an ongoing process that is taking place in the present. 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 occur are often visible. It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The reason is that different characteristics result in different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next. In the past, if one particular allele – the genetic sequence that controls coloration – was present in a group of interbreeding organisms, it might quickly become more prevalent than the other alleles. Over time, this would mean that the number of moths sporting black pigmentation in a group may increase. The same is true for many other characteristics—including morphology and behavior—that vary among populations of organisms. It is easier to observe evolution when an organism, like bacteria, has a rapid generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each are taken regularly, and over 50,000 generations have now been observed. Lenski's work has shown that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also shows that evolution takes time, a fact that some people find difficult to accept. Another example of microevolution is that mosquito genes that confer resistance to pesticides are more prevalent in populations in which insecticides are utilized. That's because the use of pesticides creates a pressure that favors people with resistant genotypes. The speed of evolution taking place has led to an increasing recognition of its importance in a world shaped by human activity—including climate change, pollution, and the loss of habitats which prevent many species from adapting. Understanding the evolution process can help us make better decisions regarding the future of our planet as well as the life of its inhabitants.