The Academy's Evolution Site Biology is one of the most central concepts in biology. The Academies are committed to helping those who are interested in science to learn about the theory of evolution and how it is permeated in all areas of scientific research. This site provides a range of sources for teachers, students, and general readers on evolution. It also includes important video clips 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 appears in many religions and cultures as an emblem of unity and love. It has many practical applications as well, such as providing a framework to understand the history of species and how they react to changing environmental conditions. Early attempts to describe the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, based on sampling of different parts of living organisms, or sequences of short fragments of their DNA, significantly increased the variety that could be represented in the tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is still largely unrepresented3,4. Genetic techniques have greatly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular methods enable us to create trees by using sequenced markers, such as the small subunit of ribosomal RNA gene. Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially true for microorganisms that are difficult to cultivate and which are usually only found in a single specimen5. Recent analysis of all genomes produced a rough draft of a Tree of Life. This includes a variety of archaea, bacteria and other organisms that have not yet been identified or whose diversity has not been well understood6. This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine if certain habitats require special protection. This information can be utilized in a variety of ways, from identifying new treatments to fight disease to improving crop yields. The information is also beneficial to conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with potentially significant metabolic functions that could be at risk of anthropogenic changes. Although funding to protect biodiversity are crucial, ultimately the best way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to act locally in order to promote conservation from within. Phylogeny A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Scientists can create a phylogenetic chart that shows the evolution of taxonomic groups using molecular data and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution. A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms with similar characteristics and have evolved from an ancestor that shared traits. These shared traits could be homologous, or analogous. Homologous traits are similar in terms of their evolutionary path. Analogous traits might appear like they are but they don't have the same origins. Scientists organize similar traits into a grouping referred to as a Clade. All members of a clade have a common trait, such as amniotic egg production. They all came 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. Scientists utilize DNA or RNA molecular data to construct a phylogenetic graph that is more precise and detailed. ???? ??? ???? is more precise and gives evidence of the evolution history of an organism. Researchers can utilize Molecular Data to calculate the evolutionary age of organisms and identify how many species have an ancestor common to all. The phylogenetic relationship can be affected by a variety of factors that include the phenotypic plasticity. This is a type behaviour that can change in response to particular environmental conditions. This can cause a characteristic to appear more like a species another, clouding the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous features in the tree. Additionally, phylogenetics aids predict the duration and rate 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's the conservation of phylogenetic variety that will result in an ecosystem that is complete and balanced. Evolutionary Theory The central theme of evolution is that organisms develop various characteristics over time due to their interactions with their surroundings. Many scientists have developed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would evolve according to its own needs and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can cause changes that are passed on to the In the 1930s and 1940s, theories from various fields, such as natural selection, genetics & particulate inheritance, merged to form a contemporary evolutionary theory. This defines how evolution occurs by the variation of genes in the population, and how these variants alter over time due to natural selection. This model, called genetic drift mutation, gene flow and sexual selection, is the foundation of modern evolutionary biology and can be mathematically explained. Recent discoveries in the field of evolutionary developmental biology have demonstrated the ways in which variation can be introduced to a species via mutations, genetic drift and reshuffling of genes during sexual reproduction, and even migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to evolution that is defined as changes in the genome of the species over time and also by changes in phenotype over time (the expression of the genotype in the individual). Students can gain a better understanding of phylogeny by incorporating evolutionary thinking throughout all areas of biology. In a study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution increased their understanding of evolution during the course of a college biology. For more information on how to teach about evolution, please look up The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education. Evolution in Action Scientists have studied evolution through looking back in the past, studying fossils, and comparing species. They also study living organisms. Evolution isn't a flims moment; it is an ongoing process. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs and animals change their behavior to a changing planet. The changes that result are often evident. But it wasn't until the late 1980s that biologists realized that natural selection could be seen in action, as well. The reason is that different traits confer different rates of survival and reproduction (differential fitness), and can be passed down from one generation to the next. In ???? ??? ?? , if one allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it could be more common than any other allele. As time passes, this could mean that the number of moths that have 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 evolution when the species, like bacteria, has a rapid generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each are taken regularly and more than 500.000 generations have been observed. Lenski's research has revealed that a mutation can dramatically alter the speed at which a population reproduces--and so the rate at which it alters. It also demonstrates that evolution takes time, something that is difficult for some to accept. Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in populations that have used insecticides. That's because the use of pesticides creates a selective pressure that favors individuals with resistant genotypes. The rapid pace of evolution taking place has led to a growing awareness of its significance in a world that is shaped by human activities, including climate changes, pollution and the loss of habitats that hinder the species from adapting. Understanding the evolution process can aid you in making better decisions about the future of the planet and its inhabitants.
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