The Academy's Evolution Site
Biology is one of the most important concepts in biology. The Academies are committed to helping those who are interested in the sciences understand evolution theory and how it is permeated throughout all fields of scientific research.
This site provides students, teachers and general readers with a wide range of learning resources about 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 religions and cultures as a symbol of unity and love. It can be used in many practical ways as well, including providing a framework to understand the history of species and how they respond to changing environmental conditions.
The first attempts to depict the biological world were built on categorizing organisms based on their metabolic and physical characteristics. These methods rely on the collection of various parts of organisms or short fragments of DNA have significantly increased the diversity of a Tree of Life2. These trees are mostly populated by eukaryotes, and bacteria are largely underrepresented3,4.
In avoiding the necessity of direct observation and experimentation, genetic techniques have enabled us to represent the Tree of Life in a more precise way. Trees can be constructed using molecular methods, such as the small-subunit ribosomal gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is particularly relevant to microorganisms that are difficult to cultivate, and are typically present in a single sample5. Recent analysis of all genomes resulted in a rough draft of a Tree of Life. This includes a wide range of archaea, bacteria, and other organisms that haven't yet been isolated or their diversity is not thoroughly understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if particular habitats need special protection. This information can be utilized in a variety of ways, such as finding new drugs, battling diseases and improving the quality of crops. The information is also incredibly useful for conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with significant metabolic functions that could be vulnerable to anthropogenic change. While funds to protect biodiversity are important, the most effective way to conserve the world's biodiversity is to equip more people in developing countries with the information they require to take action locally and encourage conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. By using molecular information as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that evolved from common ancestral. These shared traits can be homologous, or analogous. Homologous traits are the same in terms of their evolutionary paths. Analogous traits could appear like they are but they don't share the same origins. Scientists put similar traits into a grouping known as a Clade. All organisms in a group share a characteristic, like amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the species that are most closely related to each other.
Scientists utilize DNA or RNA molecular information to create a phylogenetic chart which is more precise and detailed. This data is more precise than morphological data and gives evidence of the evolutionary history of an organism or group. Researchers can utilize Molecular Data to calculate the age of evolution of organisms and determine the number of organisms that share the same ancestor.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic plasticity a type of behavior that alters in response to specific environmental conditions. This can cause a characteristic to appear more resembling to one species than another which can obscure the phylogenetic signal. This issue can be cured by using cladistics, which incorporates the combination of analogous and homologous features in the tree.
Furthermore, phylogenetics may aid in predicting the duration and rate of speciation. This information can assist conservation biologists in deciding which species to protect from the threat of extinction. Ultimately, it is the preservation of phylogenetic diversity which will lead to a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism would evolve according to its individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of traits can lead to changes that are passed on to the
In the 1930s & 1940s, ideas from different areas, including genetics, natural selection, and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This explains 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, called genetic drift or mutation, gene flow and sexual selection, is the foundation of current evolutionary biology, and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variations can be introduced into a species via genetic drift, mutation, and reshuffling genes during sexual reproduction, and also by migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in 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 that genotype in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny as well as evolution. In a recent study conducted by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in an undergraduate biology course. For more details on how to teach evolution, see The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution through looking back in the past--analyzing fossils and comparing species. They also observe living organisms. Evolution is not a past event, but an ongoing process. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of the changing environment. The changes that occur are often visible.
But 무료 에볼루션 wasn't until the late-1980s that biologists realized that natural selection could be observed in action as well. The reason is that different traits confer different rates of survival and reproduction (differential fitness) and can be transferred from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour - was found in a group of organisms that interbred, it might become more prevalent than any other allele. In time, this could mean that the number of moths sporting black pigmentation in a 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 fast generation turnover such as bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each are taken every day, and over fifty thousand generations have passed.
Lenski's research has revealed that a mutation can dramatically alter the speed at which a population reproduces and, consequently the rate at which it alters. It also proves that evolution takes time--a fact that some find difficult to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides appear more frequently in areas in which insecticides are utilized. This is due to pesticides causing a selective pressure which favors those with 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 activity--including climate change, pollution, and the loss of habitats which prevent many species from adjusting. Understanding evolution can help us make smarter decisions about the future of our planet and the lives of its inhabitants.