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The Academy's Evolution Site
Biology is one of the most fundamental concepts in biology. The Academies are involved in helping those interested in science to learn about the theory of evolution and how it can be applied throughout all fields of scientific research.
This site provides a wide range of resources for teachers, students 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, symbolizes the interconnectedness of all life. It is a symbol of love and unity in many cultures. It has numerous practical applications as well, such as providing a framework to understand the evolution of species and how they react to changing environmental conditions.
Early approaches to depicting the world of biology focused on the classification of organisms into distinct categories which had been identified by their physical and metabolic characteristics1. These methods are based on the sampling of different parts of organisms, or fragments of DNA, have significantly increased the diversity of a Tree of Life2. However these trees are mainly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
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 using molecular methods like the small-subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is particularly the case for microorganisms which are difficult to cultivate, and are usually present in a single sample5. A recent study of all genomes that are known has produced a rough draft version of the Tree of Life, including many archaea and bacteria that are not isolated and their diversity is not fully understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine if specific habitats require protection. This information can be utilized in a variety of ways, from identifying the most effective remedies to fight diseases to improving crops. It is also valuable to conservation efforts. 에볼루션 바카라 무료체험 can help biologists identify the areas that are most likely to contain cryptic species with important metabolic functions that could be vulnerable to anthropogenic change. While funding to protect biodiversity are important, the most effective way to conserve the world's biodiversity is to equip more people in developing countries with the knowledge they need to take action locally and encourage conservation.
에볼루션 무료체험 is also known as an evolutionary tree, shows the relationships between various groups of organisms. Using molecular data, morphological similarities and differences or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits are either homologous or analogous. Homologous traits share their evolutionary roots and analogous traits appear similar, but do not share the same ancestors. Scientists organize similar traits into a grouping called a the clade. All organisms in a group share a characteristic, like amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms who are the closest to each other.
Scientists make use of molecular DNA or RNA data to build a phylogenetic chart which is more precise and precise. This information is more precise than morphological data and gives evidence of the evolutionary background of an organism or group. Researchers can utilize Molecular Data to determine the evolutionary age of organisms and identify how many organisms have an ancestor common to all.
The phylogenetic relationships between species are influenced by many factors, including phenotypic plasticity a type of behavior that changes in response to unique environmental conditions. This can cause a particular trait to appear more similar in one species than another, clouding the phylogenetic signal. This issue can be cured by using cladistics, which is a the combination of homologous and analogous features in the tree.
In addition, phylogenetics can aid in predicting the length and speed of speciation. This information can aid conservation biologists to make decisions about the species they should safeguard from the threat of extinction. In the end, it's the conservation of phylogenetic variety that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire distinct characteristics over time due to their interactions with their environments. Many scientists have come up with 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 individual requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern hierarchical system of taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of certain traits can result in changes that are passed on to the next generation.
In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection and particulate inheritance -- came together to form the modern evolutionary theory synthesis that explains how evolution is triggered by the variation of genes within a population, and how those variants change over time as a result of natural selection. This model, which is known as genetic drift or mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have shown how variation can be introduced to a species by mutations, genetic drift and reshuffling of genes during sexual reproduction and the movement between populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of the 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 as time passes (the expression of that genotype in the individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking in all areas of biology. A recent study conducted by Grunspan and colleagues, for instance, showed that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college-level biology class. For more information about how to teach evolution, see The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily: a Framework for Integrating 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 isn't a flims moment; it is an ongoing process that continues to be observed today. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of a changing world. The changes that result are often visible.
It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The key to this is that different traits can confer a different rate of survival as well as reproduction, and may be passed down from one generation to another.
In the past, if one particular allele - the genetic sequence that determines coloration--appeared in a group of interbreeding organisms, it might quickly become more common than other alleles. Over time, this would mean that the number of moths with black pigmentation 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 species has a rapid generation turnover, as with bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples from each population are taken regularly and more than 50,000 generations have now passed.
Lenski's research has revealed that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently, the rate at which it evolves. It also shows that evolution is slow-moving, a fact that some are unable to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides appear more frequently in areas where insecticides are employed. This is because pesticides cause a selective pressure which favors those who have resistant genotypes.
The rapid pace at which evolution takes place has led to a growing appreciation of its importance in a world that is shaped by human activities, including climate changes, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution will help us make better decisions about the future of our planet, as well as the lives of its inhabitants.