The Academy's Evolution Site Biology is one of the most important concepts in biology. The Academies have been for a long time involved in helping people who are interested in science comprehend the theory of evolution and how it influences all areas of scientific exploration. This site provides a range of tools for students, teachers as well as general readers about evolution. It includes key video clip 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 a symbol of love and unity in many cultures. It can be used in many practical ways as well, including providing a framework for understanding the history of species and how they respond to changes in environmental conditions. Early attempts to represent the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods rely on the sampling of different parts of organisms or short fragments of DNA, have greatly increased the diversity of a Tree of Life2. The trees are mostly composed by eukaryotes, and bacterial diversity is vastly underrepresented3,4. Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees using molecular techniques, such as the small-subunit ribosomal gene. Despite the dramatic growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually only present in a single sample5. A recent analysis of all known genomes has created a rough draft of the Tree of Life, including many archaea and bacteria that have not been isolated and their diversity is not fully understood6. This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require special protection. This information can be utilized in a range of ways, from identifying new remedies to fight diseases to enhancing the quality of crop yields. The information is also useful for conservation efforts. It can aid biologists in identifying areas that are most likely to be home to cryptic species, which could have vital metabolic functions and be vulnerable to changes caused by humans. While conservation funds are important, the best method to protect the world's biodiversity is to empower more people in developing countries with the information they require to act locally and promote conservation. Phylogeny A phylogeny is also known as an evolutionary tree, reveals the connections between different groups of organisms. Scientists can build a phylogenetic diagram that illustrates the evolution of taxonomic groups using molecular data and morphological differences or similarities. Phylogeny is crucial in understanding biodiversity, evolution and genetics. A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestral. These shared traits could be either homologous or analogous. Homologous traits share their evolutionary origins and analogous traits appear like they do, but don't have the same ancestors. Scientists combine similar traits into a grouping called a the clade. Every organism in a group share a characteristic, like amniotic egg production. They all came from an ancestor that had these eggs. The clades then join to form a phylogenetic branch that can identify organisms that have the closest relationship to. For a more detailed and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships among organisms. This information is more precise than morphological data and gives evidence of the evolutionary history of an individual or group. The analysis of molecular data can help researchers identify the number of species that have a common ancestor and to estimate their evolutionary age. ??????? between species are influenced by many factors, including phenotypic plasticity an aspect of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than to another, obscuring the phylogenetic signals. However, this issue can be solved through the use of methods such as cladistics which include a mix of homologous and analogous features into the tree. Additionally, phylogenetics can help determine the duration and speed at which speciation takes place. This information can aid conservation biologists to make decisions about the species they should safeguard from extinction. Ultimately, it is the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced. Evolutionary Theory The central theme 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 wide range of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its needs and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that can be passed on to the offspring. In the 1930s and 1940s, concepts from various fields, including natural selection, genetics, and particulate inheritance - came together to form the modern synthesis of evolutionary theory, which defines how evolution is triggered by the variations of genes within a population, and how those variations change in time due to natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is the foundation of the current evolutionary biology and is mathematically described. Recent discoveries in the field of evolutionary developmental biology have shown that variations can be introduced into a species via mutation, genetic drift, and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, along with others such as directional selection and gene erosion (changes in frequency of genotypes over time) can result in evolution. Evolution is defined as changes in the genome over time and changes in phenotype (the expression of genotypes within individuals). Students can gain a better understanding of phylogeny by incorporating evolutionary thinking in all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance, showed that teaching about the evidence supporting evolution increased students' understanding of evolution in a college biology class. For more information on how to teach about evolution, please see The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education. Evolution in Action Scientists have traditionally looked at evolution through the past, studying fossils, and comparing species. They also observe 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 evolve to stay away from new medications and bacteria mutate to resist antibiotics. Animals alter their behavior as a result of a changing environment. The resulting changes are often easy to see. It wasn't until late-1980s that biologists realized that natural selection could be observed in action as well. The key is the fact that different traits can confer a different rate of survival and reproduction, and can be passed on 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. As time passes, this could mean that the number of moths that have black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms. The ability to observe evolutionary change is easier when a particular species has a rapid generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. Samples of each population were taken frequently and more than 500.000 generations of E.coli have passed. Lenski's research has shown that a mutation can profoundly alter the speed at which a population reproduces--and so, the rate at which it alters. It also shows evolution takes time, a fact that is hard for some to accept. Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations that have used insecticides. This is because pesticides cause a selective pressure which favors individuals who have resistant genotypes. The rapidity of evolution has led to a greater awareness of its significance especially in a planet shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss, which 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.
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