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The Academy's Evolution Site Biology is a key concept in biology. The Academies are committed to helping those interested in the sciences understand evolution theory and how it can be applied 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 clip from NOVA and WGBH produced 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 spiritual traditions and cultures as an emblem of unity and love. It has numerous practical applications as well, such as providing a framework to understand the evolution of species and how they respond to changes in environmental conditions. Early attempts to describe 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 organisms or fragments of DNA, have significantly increased the diversity of a Tree of Life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4. Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques enable us to create trees using sequenced markers, such as the small subunit ribosomal gene. The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true for microorganisms, which are difficult to cultivate and are usually only found in a single specimen5. A recent analysis of all genomes produced a rough draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that haven't yet been isolated or whose diversity has not been well understood6. This expanded Tree of Life can be used to determine the diversity of a specific region and determine if particular 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 extremely beneficial for conservation efforts. It can help biologists identify areas that are most likely to be home to species that are cryptic, which could have vital metabolic functions, and could be susceptible to the effects of human activity. While funding to protect biodiversity are essential, the best method to preserve the world's biodiversity is to equip more people in developing countries with the information they require to act locally and support conservation. Phylogeny A phylogeny, also known as an evolutionary tree, reveals the relationships between different groups of organisms. Utilizing molecular data as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution. A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits can be either analogous or homologous. Homologous traits are similar in their evolutionary roots while analogous traits appear similar, but do not share the same origins. Scientists arrange similar traits into a grouping referred to as a the clade. For instance, all the organisms in a clade share the characteristic of having amniotic eggs and evolved from a common ancestor who had these eggs. A phylogenetic tree is constructed by connecting the clades to determine the organisms who are the closest to each other. Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more precise and precise. This information is more precise than morphological data and provides evidence of the evolutionary history of an organism or group. Molecular data allows researchers to determine the number of organisms that have a common ancestor and to estimate their evolutionary age. The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic plasticity a kind of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more resembling to one species than another and obscure the phylogenetic signals. This problem can be addressed by using cladistics. This is a method that incorporates a combination of analogous and homologous features in the tree. Additionally, phylogenetics can help determine the duration and speed at which speciation takes place. This information can help conservation biologists make decisions about which species they should protect from the threat of extinction. Ultimately, it is the preservation of phylogenetic diversity which will create an ecologically balanced and complete ecosystem. Evolutionary Theory The central theme in evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide variety 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 as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that can be passed on to the offspring. In the 1930s & 1940s, ideas from different fields, including natural selection, genetics & particulate inheritance, were brought together to create a modern evolutionary theory. This describes how evolution happens through the variation in genes within a population and how these variants alter over 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 shown that variation can be introduced into a species via genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also through the movement of populations. 에볼루션 블랙잭 , along with others like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to evolution that is defined as changes in the genome of the species over time, and also the change in phenotype as time passes (the expression of that genotype in the individual). Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolution. In a recent study by Grunspan and colleagues. It was found that teaching students about the evidence for evolution increased their understanding of evolution during a college-level course in biology. For more details on how to teach about evolution, see The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education. Evolution in Action Traditionally scientists have studied evolution by studying fossils, comparing species, and studying living organisms. But evolution isn't just something that happened in the past. It's an ongoing process that is taking place right now. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior as a result of a changing world. The changes that result are often visible. It wasn't until late 1980s that biologists realized that natural selection can be seen in action, as well. The key is that different characteristics result in different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next. In the past when one particular allele, the genetic sequence that defines color 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 could increase. The same is true for many other characteristics—including morphology and behavior—that vary among populations of organisms. It is easier to observe evolutionary change when the species, like bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples from each population are taken regularly and more than fifty thousand generations have been observed. Lenski's work has shown that mutations can alter the rate of change and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time, a fact that is hard for some to accept. Another example of microevolution is how mosquito genes that confer resistance to pesticides are more prevalent in populations in which insecticides are utilized. This is due to pesticides causing a selective pressure which favors individuals who have resistant genotypes. The rapidity of evolution has led to an increasing appreciation of its importance particularly 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 the evolution process can help us make smarter decisions regarding the future of our planet and the lives of its inhabitants.