The Academy's Evolution Site
Biology is one of the most central concepts in biology. The Academies have been for a long time involved in helping people who are interested in science comprehend the concept of evolution and how it influences all areas of scientific research.
This site provides a range of sources for students, teachers and general readers of evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is used in many cultures and spiritual beliefs as an emblem of unity and love. It has many practical applications as well, including providing a framework to understand the evolution of species and how they respond to changing environmental conditions.
Early attempts to describe 에볼루션 무료체험 of biology were based on categorizing organisms based on their metabolic and physical characteristics. These methods, which relied on the sampling of various parts of living organisms or sequences of small DNA fragments, greatly increased the variety of organisms that could be included in the tree of life2. These trees are largely composed by eukaryotes and bacteria are largely underrepresented3,4.
Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees using molecular techniques, such as the small-subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to 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 study of all known genomes has created a rough draft of the Tree of Life, including many archaea and bacteria that have not been isolated, and their diversity is not fully understood6.
This expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if specific habitats require special protection. This information can be utilized in a variety of ways, including finding new drugs, fighting diseases and improving the quality of crops. This information is also extremely valuable in conservation efforts. It helps biologists determine the areas most likely to contain cryptic species that could have important metabolic functions that could be at risk from anthropogenic change. While funds 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 necessary knowledge to act locally and promote conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) illustrates the relationship between organisms. Scientists can construct a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that have evolved from common ancestors. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary origins, while analogous traits look similar, but do not share the identical origins. Scientists organize similar traits into a grouping called a the clade. For example, all of the organisms that make up a clade share the trait of having amniotic egg and evolved from a common ancestor that had eggs. The clades then join to form a phylogenetic branch that can identify organisms that have the closest connection to each other.
Scientists utilize molecular DNA or RNA data to build a phylogenetic chart that is more accurate and detailed. This information is more precise and provides evidence of the evolution of an organism. The use of molecular data lets researchers determine the number of organisms that share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between species are influenced by many factors including phenotypic plasticity, a type of behavior that changes in response to unique environmental conditions. This can cause a particular 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 homologous and analogous features in the tree.
Additionally, phylogenetics aids determine the duration and speed of speciation. This information can assist conservation biologists in deciding which species to save from the threat of extinction. In the end, it's the preservation of phylogenetic diversity which will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to 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 develop according to its own requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical system of taxonomy and Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of certain traits can result in changes that are passed on to the
In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection, and particulate inheritance -- came together to form the modern evolutionary theory which explains how evolution happens through the variation of genes within a population, and how these variants change over time due to natural selection. This model, which incorporates mutations, genetic drift in gene flow, and sexual selection, can be mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed how variations can be introduced to a species through mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution that is defined as change in the genome of the species over time, and also the change in phenotype as time passes (the expression of that genotype within the individual).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking throughout all areas of biology. In a study by Grunspan et al. 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 information on how to teach evolution, see The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. Evolution isn't a flims event, but an ongoing process that continues to be observed today. Bacteria mutate and resist antibiotics, viruses evolve and are able to evade new medications and animals change their behavior in response to the changing climate. The resulting changes are often visible.
It wasn't until the 1980s when biologists began to realize that natural selection was in play. The key to this is that different traits confer the ability to survive at different rates as well as reproduction, and may be passed down from generation to generation.
In the past, if one allele - the genetic sequence that determines colour - appeared in a population of organisms that interbred, it could become more common than other allele. As time passes, that could mean 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.
Monitoring evolutionary changes in action is easier when a species has a rapid generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples of each population have been collected regularly and more than 50,000 generations of E.coli have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the efficiency with which a population reproduces--and so, the rate at which it evolves. It also demonstrates that evolution is slow-moving, a fact that some people find difficult to accept.
Another example of microevolution is that mosquito genes that confer resistance to pesticides are more prevalent in areas where insecticides are used. Pesticides create a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance, especially in a world shaped largely by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding the evolution process can help us make smarter decisions regarding the future of our planet, as well as the lives of its inhabitants.