The Academy's Evolution Site
Biology is a key concept in biology. The Academies have long been involved in helping people who are interested in science comprehend the concept of evolution and how it permeates all areas of scientific exploration.
This site provides students, teachers and general readers with a variety of educational resources on evolution. It includes the most important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of life. It is used in many spiritual traditions and cultures as a symbol of unity and love. It also has practical applications, such as providing a framework to understand the evolution of species and how they respond to changes in environmental conditions.
The earliest attempts to depict the biological world focused on the classification of organisms into distinct categories which had been distinguished by physical and metabolic characteristics1. These methods, based on the sampling of various parts of living organisms, or short fragments of their DNA significantly expanded the diversity that could be included in the tree of life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
In avoiding the necessity of direct observation and experimentation, genetic techniques have enabled us to depict the Tree of Life in a more precise manner. We can create trees by using molecular methods like the small-subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is especially true of microorganisms, which are difficult to cultivate and are often only present in a single specimen5. A recent study 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 whose diversity is poorly understood6.
The expanded Tree of Life can be used to determine the diversity of a specific area and determine if specific habitats need special protection. The information is useful in a variety of ways, including identifying new drugs, combating diseases and improving crops. It is also useful in conservation efforts. It helps biologists discover areas that are most likely to be home to cryptic species, which could perform important metabolic functions, and could be susceptible to human-induced change. While funds to protect biodiversity are important, the most effective method to preserve the biodiversity of the world is to equip the people of developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. By using 에볼루션 게이밍 and differences in morphology, or ontogeny (the course of development of an organism), scientists can build an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that have evolved from common ancestors. 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 origins. Scientists combine similar traits into a grouping referred to as a clade. For instance, all of the organisms that make up a clade have the characteristic of having amniotic eggs and evolved from a common ancestor who had these eggs. The clades then join to form a phylogenetic branch to determine the organisms with the closest relationship to.
For a more detailed and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the connections between organisms. This data is more precise than morphological information and gives evidence of the evolutionary history of an individual or group. Molecular data allows researchers to identify the number of species that share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships of organisms can be affected by a variety of factors including phenotypic plasticity, a type of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than to another and obscure the phylogenetic signals. This issue can be cured by using cladistics. This is a method that incorporates the combination of homologous and analogous features in the tree.
Additionally, phylogenetics can help predict the duration and rate of speciation. This information can assist conservation biologists in making decisions about which species to safeguard from disappearance. Ultimately, it is the preservation of phylogenetic diversity which will lead to an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme in evolution is that organisms change over time due to their interactions with their environment. Several theories of evolutionary change have been developed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to offspring.
In the 1930s & 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance, merged to form a modern evolutionary theory. This describes how evolution is triggered by the variation in genes within the population and how these variations change over time as a result of 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 genetic variation can be introduced into a species through mutation, genetic drift, and reshuffling genes during sexual reproduction, and also through migration between populations. These processes, along with other ones like directionally-selected selection and erosion of genes (changes to 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 phenotype (the expression of genotypes in an individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college-level biology course. For more information on how to teach about evolution, please look up 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 traditionally studied evolution by looking in the past, analyzing fossils and comparing species. They also study living organisms. However, evolution isn't something that occurred in the past. It's an ongoing process happening today. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior as a result of a changing world. The changes that result are often visible.
But it wasn't until the late 1980s that biologists realized that natural selection could be observed in action as well. The key to this is that different traits confer the ability to survive at different rates and reproduction, and can be passed on from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour - appeared in a population of organisms that interbred, it might become more common than other allele. In time, this could mean that the number of moths that have black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to observe evolutionary change 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 from each population are taken every day and more than fifty thousand generations have been observed.
Lenski's research has shown that a mutation can profoundly alter the speed at the rate at which a population reproduces, and consequently the rate at which it changes. It also shows evolution takes time, which is difficult for some to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in areas that have used insecticides. This is because the use of pesticides creates a selective pressure that favors people with resistant genotypes.
The speed at which evolution takes place has led to an increasing recognition of its importance in a world that is shaped by human activity--including climate changes, pollution and the loss of habitats that prevent the species from adapting. Understanding evolution can assist you in making better choices regarding the future of the planet and its inhabitants.