The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been active for a long time in helping people who are interested in science understand the theory of evolution and how it affects all areas of scientific exploration.
This site provides a range of tools for teachers, students and general readers of evolution. It contains the most important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and unity across many cultures. It also has important practical applications, such as providing a framework for understanding the evolution of species and how they react to changes in environmental conditions.
The first attempts at depicting the world of biology focused on the classification of organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods, which relied on the sampling of various parts of living organisms, or sequences of short DNA fragments, greatly increased the variety of organisms that could be represented in the tree of life2. These trees are largely composed by eukaryotes, and bacterial diversity is vastly underrepresented3,4.
By avoiding the need for direct experimentation and observation, genetic techniques have made it possible to represent the Tree of Life in a more precise way. We can construct trees using molecular techniques like the small-subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of diversity to be discovered. This is especially true for microorganisms that are difficult to cultivate, and which are usually only found in a single specimen5. A recent analysis of all known genomes has produced a rough draft version of the Tree of Life, including a large number of bacteria and archaea that have not been isolated and which are not well understood.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if specific habitats require protection. The information can be used in a variety of ways, from identifying new medicines to combating disease to enhancing the quality of the quality of crops. The information is also valuable in conservation efforts. It can help biologists identify areas most likely to be home to cryptic species, which could have important metabolic functions, and could be susceptible to human-induced change. While funds to protect biodiversity are crucial however, the most effective method to protect the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can create a phylogenetic chart that shows the evolution 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 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits could be analogous or homologous. Homologous traits are similar in their evolutionary origins and analogous traits appear like they do, but don't have the identical origins. Scientists put similar traits into a grouping called a Clade. All members of a clade have a common characteristic, for example, amniotic egg production. They all derived from an ancestor who had these eggs. The clades then join to create a phylogenetic tree to identify organisms that have the closest relationship.
Scientists utilize molecular DNA or RNA data to construct a phylogenetic graph which is more precise and detailed. This information is more precise and gives evidence of the evolution of an organism. Molecular data allows researchers to determine the number of organisms that have a common ancestor and to estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors that include the phenomenon of phenotypicplasticity. This is a kind of behavior that alters in response to specific environmental conditions. This can cause a trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates an amalgamation of analogous and homologous features in the tree.
Additionally, phylogenetics aids determine the duration and rate of speciation. This information can aid conservation biologists to decide the species they should safeguard from extinction. In the end, it is the preservation of phylogenetic diversity which will create 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 proposed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism would evolve according to its individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can cause changes that are passed on to the next generation.
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 which explains how evolution happens through the variations of genes within a population, and how those variations change in time due to natural selection. This model, known as genetic drift mutation, gene flow and sexual selection, is the foundation of current evolutionary biology, and can be mathematically explained.
Recent advances in the field of evolutionary developmental biology have revealed the ways in which variation can be introduced to a species via mutations, genetic drift, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to evolution which is defined by changes in the genome of the species over time and also the change in phenotype over time (the expression of the genotype in the individual).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking throughout all aspects of biology. In a recent study by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution during the course of a college biology. To learn more about 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.
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Traditionally, scientists have studied evolution by studying fossils, comparing species, and observing living organisms. Evolution is not a past event, but an ongoing process. Bacteria evolve and resist antibiotics, viruses evolve and are able to evade new medications and animals alter their behavior in response to the changing environment. The results are often visible.
It wasn't until late 1980s when biologists began to realize that natural selection was also in play. The main reason is that different traits can confer the ability to survive at different rates and reproduction, and can be passed on from one generation to another.
In the past, if an allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it could become more common than other allele. As time passes, that could mean that the number of black moths within 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 observe evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. The samples of each population were taken regularly, and more than 500.000 generations of E.coli have passed.
Lenski's research has revealed that mutations can alter the rate of change and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time--a fact that many are unable to accept.
Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides have been used. That's because the use of pesticides creates a selective pressure that favors those who have resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance, especially in a world that is largely shaped by human activity. 에볼루션 무료체험 includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.