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 sources for teachers, students and general readers of evolution. Our Site 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 a symbol of love and unity across many cultures. It has numerous practical applications as well, such as providing a framework to understand the history of species and how they react to changing environmental conditions.
Early attempts to represent the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on sampling of different parts of living organisms, or small DNA fragments, significantly increased the variety that could be included in a tree of life2. However these trees are mainly made up of eukaryotes. Bacterial diversity remains vastly underrepresented3,4.
By avoiding the necessity for direct experimentation and observation, genetic techniques have made it possible to represent the Tree of Life in a more precise manner. Particularly, molecular methods allow us to build trees using sequenced markers like the small subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is a lot of diversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate, and are typically found in one sample5. Recent analysis of all genomes produced a rough draft of a Tree of Life. This includes a large number of bacteria, archaea and other organisms that haven't yet been identified or the diversity of which is not thoroughly understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, which can help to determine whether specific habitats require protection. This information can be utilized in a range of ways, from identifying the most effective remedies to fight diseases to improving crop yields. It is also beneficial for conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. Although funding to protect biodiversity are crucial but the most effective way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny is also known as an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can build a phylogenetic chart that shows the evolutionary relationships between taxonomic groups using molecular data and morphological similarities or differences. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary paths. Analogous traits might appear like they are however they do not have the same ancestry. Scientists organize similar traits into a grouping referred to as a the clade. Every organism in a group have a common characteristic, like amniotic egg production. They all evolved from an ancestor with these eggs. A phylogenetic tree can be constructed by connecting clades to identify the organisms which are the closest to one another.
For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships among organisms. This information is more precise than the morphological data and provides evidence of the evolutionary background of an organism or group. The analysis of molecular data can help researchers determine the number of organisms that share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships between organisms are influenced by many factors including phenotypic plasticity, a kind of behavior that changes in response to unique environmental conditions. This can make a trait appear more similar to one species than another, obscuring the phylogenetic signals. This problem can be addressed by using cladistics, which incorporates the combination of analogous and homologous features in the tree.
In addition, phylogenetics helps determine the duration and rate at which speciation occurs. This information can aid conservation biologists in making choices about which species to protect from extinction. In the end, it's the preservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop distinct characteristics over time due to their interactions with their environment. A variety of theories about evolution have been proposed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly in accordance with its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed onto offspring.
In the 1930s & 1940s, concepts from various fields, including genetics, natural selection and particulate inheritance, came together to create a modern theorizing of evolution. This defines how evolution happens through the variation of genes in the population, and how these variations alter over time due to natural selection. This model, which incorporates mutations, genetic drift as well as gene flow and sexual selection is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species through mutation, genetic drift, and reshuffling of genes during sexual reproduction, as well as by migration between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of a genotype over time), can lead to evolution that is defined as changes in the genome of the species over time, and also by changes in phenotype over time (the expression of that genotype in an individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. A recent study conducted by Grunspan and colleagues, for example demonstrated that teaching about the evidence for evolution increased students' understanding of evolution in a college biology class. For more information about how to teach evolution read The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past, studying fossils, and comparing species. They also observe living organisms. Evolution is not a past event, but an ongoing process. Bacteria evolve and resist antibiotics, viruses reinvent themselves and elude new medications and animals change their behavior in response to a changing planet. The results are usually evident.
However, it wasn't until late-1980s that biologists realized that natural selection can be observed in action as well. The key is that different traits confer different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour - 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 moths that have black pigmentation in a population could 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 much easier when a species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. The samples of each population have been collected regularly and more than 50,000 generations of E.coli have passed.
Lenski's work has shown that mutations can alter the rate of change and the rate at which a population reproduces. It also demonstrates that evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is that mosquito genes for resistance to pesticides appear more frequently in populations where insecticides are used. 에볼루션 바카라 사이트 is due to the fact that the use of pesticides creates a selective pressure that favors people with resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance, especially in a world which is largely shaped by human activities. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding evolution can help us make smarter decisions about the future of our planet, and the life of its inhabitants.