The Academy's Evolution Site
Biological evolution 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 understand the concept of evolution and how it permeates every area of scientific inquiry.
This site provides a range of resources for students, teachers and general readers of evolution. It has key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is a symbol of love and unity across many cultures. It has numerous practical applications as well, including providing a framework for understanding the history of species and how they respond to changing environmental conditions.
The first attempts to depict the world of biology were founded on categorizing organisms on their physical and metabolic characteristics. These methods rely on the sampling of different parts of organisms or fragments of DNA have significantly increased the diversity of a tree of Life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
By avoiding the necessity for direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. We can create trees using molecular methods, such as the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is still a lot of diversity to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are often only found in a single specimen5. Recent analysis of all genomes resulted in an unfinished draft of the Tree of Life. This includes a variety of archaea, bacteria, and other organisms that haven't yet been isolated, or the diversity of which is not well understood6.
The expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if certain habitats need special protection. This information can be utilized in a variety of ways, such as finding new drugs, fighting diseases and improving the quality of crops. The information is also incredibly useful in conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. While funding to protect biodiversity are important, the most effective method to preserve the biodiversity of the world is to equip more people in developing nations with the knowledge they need to act locally and promote conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationship of taxonomic groups based on molecular data and morphological similarities or differences. The role of phylogeny is crucial in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that evolved from common ancestral. These shared traits can be analogous, or homologous. Homologous traits share their evolutionary origins while analogous traits appear like they do, but don't have the identical origins. 무료에볼루션 into a grouping referred to as a Clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree is constructed by connecting the clades to identify the organisms which are the closest to one another.
Scientists use DNA or RNA molecular information to create a phylogenetic chart which is more precise and detailed. This information is more precise and gives evidence of the evolution history of an organism. 무료에볼루션 of molecular data lets researchers determine the number of species who share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships between organisms are influenced by many factors, including phenotypic plasticity a kind of behavior that changes in response to unique environmental conditions. This can cause a characteristic to appear more similar in one species than other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics, which is a a combination of homologous and analogous features in the tree.
Furthermore, phylogenetics may help predict the time and pace of speciation. This information can assist conservation biologists make decisions about which species they should protect from the threat of extinction. Ultimately, it is the preservation of phylogenetic diversity that will create an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme of evolution is that organisms acquire distinct characteristics over time as a result of 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 a living thing would develop according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of certain traits can result in changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from various fields, including genetics, natural selection and particulate inheritance -- came together to form the modern synthesis of evolutionary theory that explains how evolution occurs through the variation of genes within a population, and how those variations change over time as a result of 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 that variation can be introduced into a species by mutation, genetic drift and reshuffling genes during sexual reproduction, as well as through migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of the genotype over time), can lead to evolution which is defined by change in the genome of the species over time and also the change in phenotype as time passes (the expression of the genotype within the individual).
Incorporating evolutionary thinking into all areas of biology education can improve student understanding of the concepts of phylogeny and evolution. In a recent study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution increased their understanding of evolution in the course of a college biology. For more details on how to teach about evolution read The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily: 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 study living organisms. However, evolution isn't something that occurred in the past, it's an ongoing process, taking place today. Bacteria evolve and resist antibiotics, viruses re-invent themselves and elude new medications and animals change their behavior to the changing environment. The changes that occur are often evident.
It wasn't until the 1980s when biologists began to realize that natural selection was also in play. The key is that various traits confer different rates of survival and reproduction (differential fitness) and are passed down from one generation to the next.
In the past when one particular allele, the genetic sequence that defines color in a group of interbreeding species, it could quickly become more prevalent than other alleles. In time, this 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.
It is easier to track evolutionary change when a species, such as bacteria, has a high generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples of each are taken every day and more than fifty thousand generations have been observed.
Lenski's work has shown that mutations can alter the rate of change and the rate at which a population reproduces. It also demonstrates that evolution takes time, a fact that is difficult for some 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 pesticides cause an enticement that favors those who have resistant genotypes.
The rapid pace of evolution taking place has led to a growing awareness of its significance in a world that is shaped by human activities, including climate changes, pollution and the loss of habitats that hinder many species from adapting. Understanding the evolution process will help us make better decisions about the future of our planet and the lives of its inhabitants.