The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have been for a long time involved in helping people who are interested in science understand the theory of evolution and how it permeates every area of scientific inquiry.
This site provides teachers, students and general readers with a wide range of learning resources on evolution. It includes important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of 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 in addition to providing a framework for understanding the history of species and how they respond to changes in environmental conditions.
Early attempts to represent the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods depend on the sampling of different parts of organisms, or fragments of DNA, have greatly increased the diversity of a tree of Life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
Genetic techniques have greatly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques enable us to create trees by using sequenced markers such as the small subunit of ribosomal RNA gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially relevant to microorganisms that are difficult to cultivate and which are usually only present in a single sample5. A recent analysis of all genomes resulted in an unfinished draft of a Tree of Life. This includes a variety of bacteria, archaea and other organisms that haven't yet been identified or their diversity is not thoroughly understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine if specific habitats require special protection. This information can be used in a variety of ways, from identifying the most effective medicines to combating disease to enhancing crop yields. The information is also useful for conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species that could have significant metabolic functions that could be at risk of anthropogenic changes. While conservation funds are important, the best method to protect the world's biodiversity is to equip more people in developing nations with the knowledge they need to act locally and promote conservation.
에볼루션카지노사이트 is also known as an evolutionary tree, illustrates the relationships between various groups of organisms. Using molecular data, morphological similarities and differences or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic categories. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and have evolved from an ancestor with common traits. These shared traits could be analogous, or homologous. Homologous characteristics are identical in terms of their evolutionary paths. Analogous traits could appear like they are but they don't have the same origins. Scientists put similar traits into a grouping known as a clade. All members of a clade have a common characteristic, like amniotic egg production. They all came from an ancestor that had these eggs. The clades are then connected to form a phylogenetic branch to determine the organisms with the closest relationship.
Scientists use DNA or RNA molecular data to construct a phylogenetic graph that is more precise and detailed. This information is more precise and gives evidence of the evolutionary history of an organism. The use of molecular data lets researchers determine the number of species that have a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a variety of factors, including phenotypicplasticity. This is a type behavior that alters due to specific environmental conditions. This can cause a trait to appear more similar in one species than another, clouding the phylogenetic signal. This issue can be cured by using cladistics, which incorporates a combination of homologous and analogous traits in the tree.
Furthermore, phylogenetics may aid in predicting the length and speed of speciation. This information can aid conservation biologists to decide which species to protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity that will lead to an ecologically balanced and complete ecosystem.
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 developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its needs and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed onto offspring.
In the 1930s and 1940s, concepts from various fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a modern synthesis of evolution theory. This describes how evolution is triggered by the variation in genes within the population, and how these variations change with time due to natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is a cornerstone of current evolutionary biology, and can be mathematically described.
Recent advances in evolutionary developmental biology have shown how variation can be introduced to a species through mutations, genetic drift and reshuffling of genes during sexual reproduction and the movement between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution which is defined by change in the genome of the species over time, and the change in phenotype over time (the expression of that genotype within the individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking throughout all aspects of biology. In a recent study conducted by Grunspan et al., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution during a college-level course in biology. For more details on how to teach evolution read The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past--analyzing fossils and comparing species. They also observe living organisms. But evolution isn't just something that happened in the past; it's an ongoing process, that is taking place right now. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior because of the changing environment. The results are often evident.
It wasn't until the late 1980s that biologists began realize that natural selection was also at work. The key is the fact that different traits result in the ability to survive at different rates and reproduction, and can be passed on from one generation to another.
In the past when one particular allele--the genetic sequence that defines color in a population of interbreeding organisms, it might rapidly become more common than all other alleles. Over time, that would mean that the number of black moths in a particular population could rise. 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 a species, such as bacteria, has a high generation turnover. 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 taken regularly and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can drastically alter the speed at which a population reproduces--and so the rate at which it changes. It also shows evolution takes time, something that is difficult for some to accept.
Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides are used. This is due to pesticides causing an enticement that favors those with resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance especially in a planet which is largely shaped by human activities. This includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding evolution will assist you in making better choices about the future of the planet and its inhabitants.