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The Academy's Evolution Site Biological evolution is one of the most fundamental concepts in biology. The Academies are involved in helping those who are interested in the sciences understand evolution theory and how it is incorporated in all areas of scientific research. This site provides teachers, students and general readers with a variety 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, an ancient symbol, represents the interconnectedness of all life. It appears in many spiritual traditions and cultures as symbolizing unity and love. It has many practical applications as well, including providing a framework to understand the evolution of species and how they respond to changes in environmental conditions. Early attempts to represent the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, which rely on the sampling of different parts of living organisms, or small fragments of their DNA, significantly increased the variety that could be included in a tree of life2. These trees are largely composed by eukaryotes, and bacteria are largely underrepresented3,4. Genetic techniques have greatly broadened our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods allow us to construct trees using sequenced markers like the small subunit ribosomal RNA gene. The Tree of Life has been significantly expanded by genome sequencing. However, there is still much biodiversity to be discovered. This is especially relevant to microorganisms that are difficult to cultivate and are typically present in a single sample5. A recent study of all genomes known to date has created a rough draft of the Tree of Life, including numerous bacteria and archaea that are not isolated and which are not well understood. This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if specific habitats require protection. This information can be utilized in a variety of ways, from identifying new treatments to fight disease to improving crops. This information is also useful for conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species that could have significant metabolic functions that could be at risk of anthropogenic changes. While just click the following document are essential, the best method to preserve the world's biodiversity is to equip more people in developing nations with the information they require to take action locally and encourage conservation. Phylogeny A phylogeny, also called an evolutionary tree, shows the connections between groups of organisms. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolution of taxonomic groups. Phylogeny is crucial in understanding evolution, biodiversity and genetics. A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar traits and evolved from an ancestor with common traits. These shared traits could be either analogous or homologous. Homologous traits are identical in their evolutionary roots, while analogous traits look like they do, but don't have the identical origins. Scientists group similar traits into a grouping known as a clade. Every organism in a group share a characteristic, for example, amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree is then constructed by connecting the clades to determine the organisms which are the closest to each other. For a more precise and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships between organisms. This information is more precise and provides evidence of the evolutionary history of an organism. The use of molecular data lets researchers identify the number of species who share a common ancestor and to estimate their evolutionary age. The phylogenetic relationships between organisms can be influenced by several factors including phenotypic plasticity, a kind of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more similar to one species than to the other which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a the combination of homologous and analogous traits in the tree. Additionally, phylogenetics can aid in predicting the time and pace of speciation. This information can assist conservation biologists in making choices about which species to safeguard from the threat of extinction. In the end, it is the preservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete. Evolutionary Theory The main idea behind evolution is that organisms acquire different features over time due to their interactions with their environment. A variety of theories about evolution have been proposed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to offspring. In the 1930s and 1940s, ideas from a variety of fields--including natural selection, genetics, and particulate inheritance -- came together to form the modern synthesis of evolutionary theory which explains how evolution happens through the variations of genes within a population, and how those variations change in time as a result of natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is the foundation of current evolutionary biology, and can be mathematically explained. Recent developments in evolutionary developmental biology have shown the ways in which variation can be introduced to a species through genetic drift, mutations and reshuffling of genes during sexual reproduction, and even migration between populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution, which is defined by change in the genome of the species over time and also by changes in phenotype as time passes (the expression of that genotype within the individual). Students can better understand the concept of phylogeny by using evolutionary thinking into all aspects of biology. In a recent study by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution boosted their acceptance of evolution during a college-level course in biology. To find out more about how to teach about evolution, please look up The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education. Evolution in Action Traditionally, scientists have studied evolution through looking back, studying fossils, comparing species, and studying living organisms. However, evolution isn't something that happened in the past; it's an ongoing process taking place today. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior in the wake of the changing environment. The results are often apparent. It wasn't until late 1980s that biologists began to realize that natural selection was in action. The key is the fact that different traits can confer an individual rate of survival and reproduction, and can be passed down from generation to generation. In the past, when one particular allele--the genetic sequence that determines coloration--appeared in a population of interbreeding organisms, it might rapidly become more common than the other alleles. As time passes, this could mean that the number of moths sporting black pigmentation in a group 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 an organism, 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 of each are taken on a regular basis, and over 50,000 generations have now passed. Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also demonstrates that evolution is slow-moving, a fact that some are unable to accept. Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides are used. That's because the use of pesticides creates a pressure that favors individuals with resistant genotypes. Full Content of evolution has led to an increasing awareness of its significance particularly in a world that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding evolution can help us make smarter decisions about the future of our planet and the life of its inhabitants.
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