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The Academy's Evolution Site The concept of biological evolution is among the most fundamental concepts in biology. The Academies are involved in helping those who are interested in science comprehend the evolution theory and how it is permeated in all areas of scientific research. This site provides a wide range of tools for teachers, students, and general readers on evolution. It 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 represents the interconnectedness of all life. It is an emblem of love and unity across many cultures. It can be used in many practical ways as well, such as providing a framework to understand the history of species and how they react to changes in environmental conditions. The first attempts at depicting the world of biology focused on the classification of organisms into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, based on the sampling of different parts of living organisms, or sequences of small fragments of their DNA significantly expanded the diversity that could be included in the tree of life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4. By avoiding the necessity for direct experimentation and observation genetic techniques have enabled us to represent the Tree of Life in a more precise manner. We can create trees using molecular techniques such as the small subunit ribosomal gene. The Tree of Life has been dramatically expanded through genome sequencing. However there is a lot of diversity to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are often only found in a single sample5. A recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated or the diversity of which is not thoroughly understood6. The expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if specific habitats need special protection. The information is useful in many ways, including finding new drugs, battling diseases and improving the quality of crops. This information is also beneficial to conservation efforts. It can aid biologists in identifying areas most likely to have cryptic species, which could have vital metabolic functions, and could be susceptible to the effects of human activity. While funds to protect biodiversity are important, the most effective method to preserve the world's biodiversity is to empower more people in developing countries with the knowledge they need to act locally and support conservation. Phylogeny A phylogeny, also called an evolutionary tree, illustrates the relationships between groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics. A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that have evolved from common ancestors. These shared traits are either analogous or homologous. Homologous traits are identical in their evolutionary origins while analogous traits appear similar, but do not share the same ancestors. Scientists group similar traits together into a grouping referred to as a Clade. All members of a clade share a trait, such as amniotic egg production. They all derived from an ancestor that had these eggs. The clades are then connected to form a phylogenetic branch to identify organisms that have the closest relationship to. Scientists make use of molecular DNA or RNA data to construct a phylogenetic graph that is more precise and precise. This information is more precise and gives evidence of the evolutionary history of an organism. The use of molecular data lets researchers identify the number of organisms who share an ancestor common to them and estimate their evolutionary age. The phylogenetic relationships between organisms can be affected by a variety of factors including phenotypic plasticity, a kind of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to a species than to the other and obscure the phylogenetic signals. However, this problem can be solved through the use of techniques like cladistics, which combine similar and homologous traits into the tree. In addition, phylogenetics helps determine the duration and speed of speciation. This information can help conservation biologists decide which species they should protect from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced. Evolutionary Theory The central theme in evolution is that organisms change over time as a result of their interactions with their environment. click through the following post of theories about evolution have been developed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its requirements and 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 causes changes that could be passed on to offspring. In the 1930s and 1940s, theories from a variety of fields—including natural selection, genetics, and particulate inheritance — came together to form the current evolutionary theory that explains how evolution occurs through the variations of genes within a population and how those variants change over time as a result of natural selection. This model, which incorporates genetic drift, mutations in gene flow, and sexual selection can be mathematically described. Recent discoveries in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species via mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also through migration between populations. These processes, as well as 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 by changes in phenotype over time (the expression of that genotype in the individual). Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking throughout all aspects of biology. In a recent study by Grunspan et al. It was found that teaching students about the evidence for evolution boosted their acceptance of evolution during an undergraduate biology course. For more details on how to teach about evolution read The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education. Evolution in Action Scientists have studied evolution through looking back in the past—analyzing fossils and comparing species. They also observe living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Bacteria mutate and resist antibiotics, viruses re-invent themselves and elude new medications, and animals adapt their behavior to the changing climate. The results are usually visible. It wasn't until the late 1980s that biologists began to realize that natural selection was in action. The reason is that different traits have different rates of survival and reproduction (differential fitness) and can be passed down from one generation to the next. In the past, if one allele – the genetic sequence that determines colour – was found in a group of organisms that interbred, it might become more common than other allele. In time, this could mean the number of black moths in the population 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 evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. Samples of each population have been taken regularly and more than 500.000 generations of E.coli have passed. Lenski's work has demonstrated that mutations can drastically alter the efficiency with the rate at which a population reproduces, and consequently the rate at which it alters. It also demonstrates that evolution is slow-moving, a fact that some people find difficult to accept. Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more prevalent in areas 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 appreciation of its importance particularly in a world that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution will help us make better choices about the future of our planet and the lives of its inhabitants.