manxcork89

The Academy's Evolution Site The concept of biological evolution is a fundamental concept in biology. The Academies have long been involved in helping those interested in science comprehend the concept of evolution and how it influences all areas of scientific exploration. This site offers a variety of sources for students, teachers as well as general readers about 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 is seen in a variety of religions and cultures as symbolizing unity and love. It can be used in many practical ways in addition to providing a framework for understanding the history of species and how they react to changes in environmental conditions. Early attempts to represent the world of biology were based on categorizing organisms based on their metabolic and physical characteristics. These methods, based on the sampling of different parts of living organisms or short fragments of their DNA, significantly expanded the diversity that could be represented in the tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4. By avoiding the need for direct observation and experimentation, genetic techniques have allowed us to depict the Tree of Life in a more precise manner. Particularly, molecular methods allow us to build trees by using sequenced markers like the small subunit of ribosomal RNA gene. Despite the massive growth of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is particularly the case for microorganisms which are difficult to cultivate, and which are usually only found in one sample5. A recent study of all known genomes has produced a rough draft version of the Tree of Life, including numerous archaea and bacteria that have not been isolated and which are not well understood. This expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if specific habitats need special protection. This information can be utilized in a variety of ways, such as identifying new drugs, combating diseases and enhancing crops. The information is also incredibly valuable in conservation efforts. It can aid biologists in identifying areas that are most likely to be home to cryptic species, which may perform important metabolic functions, and could be susceptible to changes caused by humans. While funding to protect biodiversity are important, the best method to preserve the world's biodiversity is to empower more people in developing nations with the necessary knowledge to act locally and promote conservation. Phylogeny A phylogeny (also called an evolutionary tree) illustrates the relationship between different organisms. Utilizing molecular data as well as morphological similarities and distinctions or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution. A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestors. These shared traits could be either analogous or homologous. Homologous characteristics are identical in their evolutionary paths. Analogous traits might appear similar but they don't share the same origins. Scientists arrange similar traits into a grouping known as a Clade. For instance, all of the species in a clade share the characteristic of having amniotic egg and evolved from a common ancestor who had eggs. The clades are then connected to form a phylogenetic branch that can determine which organisms have the closest connection to each other. For a more detailed and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the relationships between organisms. This information is more precise and gives evidence of the evolution of an organism. The use of molecular data lets researchers identify the number of organisms that have the same ancestor and estimate their evolutionary age. The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic flexibility, an aspect of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more similar to a species than another and obscure the phylogenetic signals. However, this issue can be cured by the use of techniques such as cladistics that combine similar and homologous traits into the tree. Additionally, phylogenetics can help determine the duration and speed at which speciation takes place. This information can assist conservation biologists in making choices about which species to safeguard from disappearance. It is ultimately the preservation of phylogenetic diversity which will result in a complete and balanced ecosystem. Evolutionary Theory The central theme of evolution is that organisms acquire distinct characteristics over time based on their interactions with their environment. A variety of theories about evolution have been developed by a wide range of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly in accordance with its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed onto offspring. In the 1930s and 1940s, theories from various areas, including genetics, natural selection and particulate inheritance, were brought together to form a contemporary synthesis of evolution theory. This defines how evolution is triggered by the variations in genes within a population and how these variants change with time due to natural selection. This model, which includes mutations, genetic drift, gene flow and sexual selection is mathematically described mathematically. Recent advances in evolutionary developmental biology have shown how variation can be introduced to a species via genetic drift, mutations, reshuffling genes during sexual reproduction, and even migration between populations. These processes, in conjunction with others such as directional selection and gene erosion (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time as well as changes in phenotype (the expression of genotypes within individuals). Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking into all aspects of biology. A recent study by Grunspan and colleagues, for instance, showed that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college biology course. For more details about how to teach evolution look up The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education. Evolution in Action Scientists have traditionally studied evolution by looking in the past—analyzing fossils and comparing species. They also study living organisms. But evolution isn't a thing that occurred in the past, it's an ongoing process happening today. The virus reinvents itself to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior in the wake of a changing environment. The changes that result are often apparent. 에볼루션 룰렛 wasn't until the late 1980s when biologists began to realize that natural selection was also at work. The key is that different characteristics result in different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next. In the past, if one allele – the genetic sequence that determines color – was found in a group of organisms that interbred, it could become more common than any other allele. In time, this could mean that 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 track evolutionary change when a species, such as bacteria, has a high generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples of each population are taken on a regular basis and over fifty thousand generations have been observed. Lenski's research has shown that mutations can drastically alter the rate at the rate at which a population reproduces, and consequently the rate at which it changes. It also shows that evolution is slow-moving, a fact that some are unable to accept. Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides have been used. This is due to pesticides causing an exclusive pressure that favors individuals who have resistant genotypes. The rapid pace at which evolution can take place has led to an increasing recognition of its importance in a world that is shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process will help you make better decisions about the future of the planet and its inhabitants.