The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have long been involved in helping people who are interested in science understand the theory of evolution and how it affects all areas of scientific research.
This site provides a wide range of resources for students, teachers as well as general readers about evolution. It contains the most 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 seen in a variety of spiritual traditions and cultures as symbolizing unity and love. It also has practical applications, such as providing a framework for understanding the history of species and how they react to changing environmental conditions.
Early approaches to depicting the world of biology focused on separating organisms into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods are based on the collection of various parts of organisms, or DNA fragments, 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.
By avoiding the necessity for direct experimentation and observation genetic techniques have allowed us to represent the Tree of Life in a more precise way. We can construct trees using molecular techniques, such as the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However, there is still much diversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually found in one sample5. 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.
The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine whether specific habitats require special protection. The information is useful in a variety of ways, such as finding new drugs, fighting diseases and enhancing 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 with significant metabolic functions that could be at risk of anthropogenic changes. While funding to protect biodiversity are important, the best method to preserve the biodiversity of the world is to equip more people in developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between different organisms. By using 에볼루션 사이트 and differences in morphology or ontogeny (the process of the development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. Phylogeny is essential 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 are either analogous or homologous. Homologous traits are similar in their evolutionary origins while analogous traits appear similar, but do not share the same origins. Scientists group similar traits together into a grouping referred to as a the clade. All members of a clade share a characteristic, for example, amniotic egg production. They all evolved from an ancestor that had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the organisms that are most closely related to one another.
Scientists utilize DNA or RNA molecular information to build a phylogenetic chart which is more precise and detailed. This information is more precise and provides evidence of the evolutionary history of an organism. Molecular data allows researchers to determine the number of species that have a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between species can be influenced by several factors including phenotypic plasticity, an aspect of behavior that changes in response to specific environmental conditions. This can cause a trait to appear more like a species other species, which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a a combination of analogous and homologous features in the tree.
In addition, phylogenetics helps determine the duration and speed at which speciation takes place. This information can help conservation biologists make decisions about which species to protect from extinction. It is ultimately the preservation of phylogenetic diversity which will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms alter over time because of 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 proposed that a living organism develop slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection and particulate inheritance - came together to form the modern evolutionary theory which explains how evolution occurs through the variation of genes within a population and how those variations change in time due to natural selection. This model, which encompasses mutations, genetic drift as well as gene flow and sexual selection is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have shown that variation can be introduced into a species via mutation, genetic drift and reshuffling of genes during sexual reproduction, and also through migration between populations. These processes, in conjunction with other ones like directional selection and gene erosion (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolutionary. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution boosted their acceptance of evolution during a college-level course in biology. For more details about how to teach evolution, see The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by looking back, studying fossils, comparing species and studying living organisms. But evolution isn't a thing that happened in the past; it's an ongoing process taking place in the present. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of a changing world. The changes that result are often easy to see.
It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The key is that various traits confer different rates of survival and reproduction (differential fitness), and can be passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it could be more prevalent than any other allele. Over time, this would mean that the number of moths sporting black pigmentation in a group could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. The samples of each population have been taken frequently and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also shows that evolution is slow-moving, a fact that many find hard to accept.
Another example of microevolution is that mosquito genes for resistance to pesticides appear more frequently in areas where insecticides are employed. This is because the use of pesticides causes a selective pressure that favors those who have resistant genotypes.
The speed of evolution taking place has led to an increasing appreciation of its importance in a world that is shaped by human activities, including climate change, pollution and the loss of habitats which prevent many species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.