The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those who are interested in the sciences learn about the theory of evolution and how it is permeated throughout all fields of scientific research.
This site provides teachers, students and general readers with a variety of educational resources on evolution. It includes key video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It appears in many cultures and spiritual beliefs as a symbol of unity and love. It has numerous practical applications in addition to providing a framework to understand the history of species and how they react to changes in environmental conditions.
The earliest attempts to depict the biological world focused on the classification of organisms into distinct categories which were distinguished by physical and metabolic characteristics1. 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. These trees are mostly populated by eukaryotes, and bacteria are largely underrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. We can construct 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 biodiversity to be discovered. This is particularly the case for microorganisms which are difficult to cultivate and which are usually only present in a single sample5. A recent analysis of all known genomes has created a rough draft of the Tree of Life, including a large number of bacteria and archaea that are not isolated and which are not well understood.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if particular habitats need special protection. This information can be utilized in a variety of ways, from identifying the most effective treatments to fight disease to enhancing the quality of the quality of crops. This information is also extremely useful in conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with significant metabolic functions that could be vulnerable to anthropogenic change. Although funding to safeguard biodiversity are vital but the most effective way to protect the world's biodiversity is for more people living in developing countries to be empowered with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between different organisms. By using molecular information as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationship between taxonomic groups. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestors. 에볼루션 shared traits can be analogous, or homologous. click through the next webpage are similar in their evolutionary path. Analogous traits could appear like they are however they do not share the same origins. Scientists arrange similar traits into a grouping called a the clade. All members of a clade share a characteristic, for example, amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree is then built by connecting the clades to determine the organisms which are the closest to each other.
Scientists utilize DNA or RNA molecular data to build a phylogenetic chart which is more precise and detailed. This information is more precise than the morphological data and provides evidence of the evolution background of an organism or group. Researchers can use Molecular Data to estimate the evolutionary age of living organisms and discover how many organisms have a common ancestor.
The phylogenetic relationships of organisms can be affected by a variety of factors, including phenotypic flexibility, a type of behavior that alters in response to specific environmental conditions. This can make a trait appear more similar to one species than to another which can obscure the phylogenetic signal. However, this problem can be reduced by the use of methods like cladistics, which combine analogous and homologous features into the tree.
Additionally, phylogenetics can aid in predicting the time and pace of speciation. This information can aid conservation biologists in deciding which species to safeguard from extinction. In the end, it is the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme of evolution is that organisms develop different features over time based on their interactions with their environments. Many theories of evolution have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly in accordance with its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that can be passed on to the offspring.
In the 1930s and 1940s, theories from various areas, including genetics, natural selection, and particulate inheritance, merged to form a contemporary synthesis of evolution theory. This explains how evolution occurs by the variation in genes within the population and how these variants alter over time due to natural selection. This model, which encompasses genetic drift, mutations, gene flow and sexual selection can be mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have demonstrated the ways in which variation can be introduced to a species via genetic drift, mutations or reshuffling of genes in sexual reproduction and the movement between populations. These processes, in conjunction with others, such as the directional selection process and the erosion of genes (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time, as well as changes in the phenotype (the expression of genotypes in individuals).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny as well as evolution. In a study 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, see The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past, studying 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 taking place right now. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of a changing world. The results are often evident.
But it wasn't until the late 1980s that biologists realized that natural selection can be seen in action, as well. The main reason is that different traits confer a different rate of survival as well as reproduction, and may be passed down 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 could become more common than other allele. As time passes, this could mean that the number of moths that have black pigmentation in a group may 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 particular species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. Samples of each population were taken regularly and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that mutations can drastically alter the rate at which a population reproduces and, consequently, the rate at which it changes. It also shows that evolution is slow-moving, a fact that some people are unable to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides are used. This is because pesticides cause a selective pressure which favors individuals who have resistant genotypes.
The rapidity of evolution has led to an increasing recognition of its importance 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 help you make better decisions about the future of our planet and its inhabitants.