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 comprehend the theory of evolution and how it affects all areas of scientific research.
This site provides a wide range of sources for students, teachers, and general readers on evolution. It includes the most important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It appears in many cultures and spiritual beliefs as a symbol of unity and love. It has numerous practical applications as well, including providing a framework to understand the history of species, and how they react to changing environmental conditions.
Early attempts to describe the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which are based on the collection of various parts of organisms or fragments of DNA have significantly increased the diversity of a Tree of Life2. These trees are largely composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.
In avoiding the necessity of direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. Particularly, molecular methods enable us to create trees using sequenced markers, such as the small subunit ribosomal RNA gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is a lot of biodiversity to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are often only present in a single specimen5. A recent study of all genomes that are known has created a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.
This expanded Tree of Life can be used to assess the biodiversity of a specific region and determine if particular habitats need special protection. This information can be utilized in a variety of ways, including finding new drugs, fighting diseases and improving crops. This information is also extremely useful in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species that could have significant metabolic functions that could be at risk of anthropogenic changes. While funds to protect biodiversity are important, the most effective way to conserve the biodiversity of the world is to equip more people in developing countries with the knowledge they need to act locally and support conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) illustrates the relationship between organisms. Scientists can construct an phylogenetic chart which shows the evolution of taxonomic groups based on molecular data and morphological differences or similarities. 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 and have evolved from an ancestor that shared traits. These shared traits can be either analogous or homologous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look similar, but do not share the same ancestors. Scientists organize similar traits into a grouping known as a clade. Every organism in a group have a common characteristic, like amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree can be constructed by connecting clades to determine the organisms who are the closest to one another.
For a more detailed and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to establish the relationships between organisms. 에볼루션사이트 is more precise than morphological data and provides evidence of the evolution history of an individual or group. 에볼루션사이트 of molecular data lets researchers identify the number of organisms who share a common ancestor and to estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors such as the phenotypic plasticity. This is a type of behavior that alters in response to specific environmental conditions. This can cause a trait to appear more like a species another, clouding the phylogenetic signal. This problem can be addressed by using cladistics, which is a a combination of analogous and homologous features in the tree.
Additionally, phylogenetics can help predict the length and speed of speciation. This information will assist conservation biologists in making decisions about which species to save from disappearance. In the end, it is the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. 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 develop according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived 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 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 modern evolutionary theory, which defines how evolution is triggered by the variation of genes within a population, and how those variants change in time due to natural selection. This model, which encompasses genetic drift, mutations in gene flow, and sexual selection is mathematically described mathematically.
Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species through mutation, genetic drift, and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, as well as others, such as the directional selection process and the erosion of genes (changes in 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 the phenotype (the expression of genotypes in individuals).
Incorporating evolutionary thinking into all aspects of biology education can improve students' understanding of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution increased students' acceptance of evolution in a college biology class. To learn more about how to teach about evolution, see The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through looking back--analyzing fossils, comparing species, and studying living organisms. But evolution isn't a thing that occurred in the past. It's an ongoing process that is taking place in the present. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs, and animals adapt their behavior to the changing climate. The changes that occur are often visible.
It wasn't until the late 1980s that biologists began realize that natural selection was also at work. The reason is that different characteristics result in different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past when one particular allele, the genetic sequence that determines coloration--appeared in a group of interbreeding organisms, it could quickly become more common than all other alleles. As time passes, that could mean that the number of black moths in a 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 an organism, like bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples of each population are taken regularly and more than 50,000 generations have now passed.
Lenski's research has demonstrated that mutations can alter the rate of change and the effectiveness at which a population reproduces. It also shows evolution takes time, something that is difficult for some to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides show up more often in populations where insecticides are used. This is due to the fact that the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution will assist you in making better choices about the future of our planet and its inhabitants.