The Academy's Evolution Site
Biology is one of the most central concepts in biology. The Academies have long been involved in helping people who are interested in science understand the theory of evolution and how it permeates all areas of scientific exploration.
This site provides teachers, students and general readers with a range of learning resources on 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, represents the interconnectedness of all life. It is an emblem of love and unity in many cultures. It also has many practical uses, like providing a framework for understanding the history of species and how they respond to changing environmental conditions.
The first attempts at depicting the world of biology focused on separating species into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms or sequences of small fragments of their DNA, significantly expanded the diversity that could be represented in a tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is still largely unrepresented3,4.
By avoiding the need for direct observation and experimentation, genetic techniques have made it possible to represent the Tree of Life in a much more accurate way. Particularly, molecular methods allow us to construct trees using sequenced markers, such as the small subunit of ribosomal RNA gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are often only found in a single sample5. A recent analysis of all genomes resulted in an initial draft of a Tree of Life. This includes a wide range of bacteria, archaea and other organisms that have not yet been identified or whose diversity has not been well understood6.
This expanded Tree of Life can be used to determine the diversity of a specific area and determine if particular habitats need special protection. 에볼루션 게이밍 can be utilized in a variety of ways, from identifying the most effective remedies to fight diseases to enhancing the quality of the quality of crops. It is also useful for conservation efforts. It can help biologists identify areas that are likely to have species that are cryptic, which could have vital metabolic functions, and could be susceptible to changes caused by humans. Although funding to safeguard biodiversity are vital but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be equipped with the knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, shows the relationships between groups of organisms. Using molecular data as well as morphological similarities and distinctions or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationships between taxonomic groups. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and have evolved from an ancestor with common traits. These shared traits can be analogous or homologous. Homologous traits are identical in their evolutionary roots while analogous traits appear similar, but do not share the same ancestors. Scientists arrange similar traits into a grouping known as a clade. For instance, all the organisms that make up a clade have the characteristic of having amniotic eggs and evolved from a common ancestor that had these eggs. A phylogenetic tree can be constructed by connecting the clades to identify the species that are most closely related to one another.
For a more detailed and precise phylogenetic tree scientists use molecular data from DNA or RNA to establish the relationships between organisms. This information is more precise than morphological data and provides evidence of the evolutionary background of an organism or group. Molecular data allows researchers to identify the number of organisms that have an ancestor common to them and 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 similar in one species than other species, which can obscure the phylogenetic signal. However, this problem can be solved through the use of methods such as cladistics which combine similar and homologous traits into the tree.
Additionally, phylogenetics can help determine the duration and rate at which speciation occurs. This information will assist conservation biologists in making choices about which species to save from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will lead to a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms change over time due to 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 own 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 believed that the usage or non-use of traits can lead to changes that are passed on to the
In the 1930s and 1940s, concepts from a variety of fields--including genetics, natural selection and particulate inheritance - came together to create the modern evolutionary theory that explains how evolution happens through the variations of genes within a population and how these variants change over time due to natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is the foundation of current evolutionary biology, and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species through genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also by migration between populations. These processes, as well as others, such as the directional selection process and the erosion of genes (changes to the 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).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking in all aspects of biology. In a recent study conducted by Grunspan et al., it was shown that teaching students about the evidence for evolution increased their acceptance of evolution during a college-level course in biology. For more information on how to teach about evolution, read The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution through looking back in the past--analyzing fossils and comparing species. They also observe living organisms. However, evolution isn't something that occurred in the past; it's an ongoing process that is taking place today. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior because of the changing environment. The changes that occur are often evident.
It wasn't until late-1980s that biologists realized that natural selection could be seen in action, as well. The main reason is that different traits confer the ability to survive at different rates and reproduction, and can be passed on from generation to generation.
In the past, if one allele - the genetic sequence that determines colour - was found in a group of organisms that interbred, it could become more common than other allele. As time passes, that could mean 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.
The ability to observe evolutionary change is easier when a particular species has a fast generation turnover like 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 regularly and over 500.000 generations have passed.
Lenski's research has shown that a mutation can dramatically alter the speed at the rate at which a population reproduces, and consequently, the rate at which it evolves. It also shows that evolution takes time, a fact that is difficult for some to accept.
Microevolution is also evident in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides are used. This is because the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance, especially in a world that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding evolution can aid you in making better decisions regarding the future of the planet and its inhabitants.