The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been for a long time involved in helping people who are interested in science understand the theory of evolution and how it influences all areas of scientific exploration.
This site provides students, teachers and general readers with a variety of educational resources on evolution. It contains key 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 an emblem of love and harmony in a variety of cultures. It has numerous practical applications in addition to providing a framework to understand the evolution of species and how they react to changing 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 various parts of living organisms or small fragments of their DNA significantly increased the variety that could be represented in the tree of life2. The trees are mostly composed by eukaryotes and the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed by using molecular methods like the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However, there is still much diversity to be discovered. This is especially true for microorganisms that are difficult to cultivate, and are typically found in one sample5. A recent study of all known genomes has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea 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 particular area and determine if specific habitats require special protection. This information can be used in many ways, including identifying new drugs, combating diseases and improving the quality of crops. It is also beneficial in conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species with potentially important metabolic functions that could be at risk of anthropogenic changes. While funds to protect biodiversity are crucial but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be equipped with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between different groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationship of taxonomic categories using molecular information and morphological similarities or differences. 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 may be analogous or homologous. Homologous traits are identical in their evolutionary origins while analogous traits appear similar, but do not share the same origins. Scientists organize similar traits into a grouping known as a Clade. 에볼루션 바카라 무료 in a group share a trait, such as amniotic egg production. They all came from an ancestor that had these eggs. The clades then join to form a phylogenetic branch to determine the organisms with the closest relationship to.
To create a more thorough and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the connections between organisms. This information is more precise and provides evidence of the evolution of an organism. Researchers can use Molecular Data to estimate the evolutionary age of organisms and identify how many organisms share a common ancestor.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic flexibility, an aspect of behavior that alters in response to specific environmental conditions. This can cause a characteristic to appear more similar to a species than another and obscure the phylogenetic signals. This problem can be mitigated by using cladistics, which incorporates a combination of homologous and analogous features in the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information can aid conservation biologists in making choices about which species to save from disappearance. In the end, it is the conservation of phylogenetic variety that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could evolve according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of certain traits can result in changes that can be passed on to future generations.
In the 1930s and 1940s, concepts from a variety of fields--including genetics, natural selection, and particulate inheritance -- came together to form the current synthesis of evolutionary theory that explains how evolution happens through the variations of genes within a population and how these variants change in time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is a key element of the current evolutionary biology and is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated the ways in which variation can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with others such as the directional selection process and the erosion of genes (changes in the frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).
Students can better understand the concept of phylogeny by using evolutionary thinking in all areas of biology. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during an undergraduate biology course. For more information on how to teach about evolution, read 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 studied evolution by looking in the past--analyzing fossils and comparing species. They also study living organisms. Evolution is not a distant moment; it is a process that continues today. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing environment. The resulting changes are often visible.
It wasn't until the 1980s that biologists began realize that natural selection was also in play. The key is the fact that different traits can confer an individual rate of survival as well as reproduction, and may be passed on from one generation to another.
In the past, if one allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it could be more common than other allele. Over time, this would mean that the number of moths that have black pigmentation may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Observing evolutionary change in action is easier when a species has a rapid generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples of each population have been collected regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the rate of a population's reproduction. It also proves that evolution is slow-moving, a fact that many find hard to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides appear more frequently in populations where insecticides are employed. That's because the use of pesticides causes a selective pressure that favors people who have resistant genotypes.
The speed at which evolution takes place has led to a growing recognition of its importance in a world shaped by human activity, including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding evolution can assist you in making better choices about the future of the planet and its inhabitants.