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The Academy's Evolution Site

The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science learn about the theory of evolution and how it is incorporated across all areas of scientific research.

This site offers a variety of tools for students, teachers as well as general readers about evolution. It includes important video clips from NOVA and the WGBH-produced science programs on DVD.

Tree of Life

The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and harmony in a variety of cultures. It has numerous practical applications in addition to providing a framework for understanding the evolution of species and how they react to changing environmental conditions.

Early attempts to describe the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods, based on the sampling of various parts of living organisms, or sequences of small fragments of their DNA significantly expanded the diversity that could be included in a tree of life2. However these trees are mainly made up of eukaryotes. Bacterial diversity is still largely unrepresented3,4.

In avoiding the necessity of direct experimentation and observation, genetic techniques have made it possible to depict the Tree of Life in a more precise way. We can construct trees by using molecular methods, 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 diversity to be discovered. This is especially the case for 에볼루션 바카라사이트 microorganisms which are difficult to cultivate, and are usually present in a single sample5. A recent analysis of all genomes resulted in a rough draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that have not yet been identified or their diversity is not well understood6.

This expanded Tree of Life can be used to determine the diversity of a specific region and determine if specific habitats need special protection. The information can be used in a variety of ways, from identifying new medicines to combating disease to enhancing the quality of crops. This information is also valuable to conservation efforts. It can help biologists identify the areas most likely to contain cryptic species with important metabolic functions that could be at risk of anthropogenic changes. Although funds to protect biodiversity are crucial but the most effective way to ensure the preservation of biodiversity around the world is for 에볼루션 게이밍 more people in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny, also known as an evolutionary tree, shows the connections between various groups of organisms. Scientists can build a phylogenetic chart that shows the evolutionary relationship of taxonomic categories using molecular information and morphological differences or similarities. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestral. These shared traits can be homologous, or analogous. Homologous traits are identical in their evolutionary origins while analogous traits appear similar, but do not share the same origins. Scientists organize similar traits into a grouping called a Clade. For instance, 에볼루션 바카라사이트 all the species in a clade share the trait of having amniotic eggs. They evolved from a common ancestor who had these eggs. A phylogenetic tree can be built by connecting the clades to identify the organisms who are the closest to each other.

To create a more thorough and precise phylogenetic tree scientists use molecular data from DNA or 에볼루션 바카라에볼루션 바카라 사이트 (m.414500.Cc) RNA to determine the relationships among organisms. This information is more precise than morphological information and gives evidence of the evolutionary history of an individual or group. Molecular data allows researchers to determine the number of species who share the same ancestor and estimate their evolutionary age.

The phylogenetic relationships of organisms can be affected by a variety of factors, including phenotypic flexibility, a type of behavior that changes in response to specific environmental conditions. This can make a trait appear more similar to one species than to another and obscure the phylogenetic signals. This problem can be mitigated by using cladistics, which incorporates a combination of homologous and analogous traits in the tree.

Additionally, phylogenetics aids determine the duration and speed at which speciation takes place. This information can aid conservation biologists to make decisions about which species they should protect from extinction. In the end, it's 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 as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly in accordance with its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed on to offspring.

In the 1930s and 1940s, theories from a variety of fields -- including genetics, natural selection, and particulate inheritance -- came together to form the modern synthesis of evolutionary theory, which defines how evolution occurs through the variation of genes within a population and how those variants change over time as a result of natural selection. This model, known as genetic drift, mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained.

Recent discoveries in the field of evolutionary developmental biology have demonstrated the ways in which variation can be introduced to a species through mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, in conjunction with other ones like directional selection and gene erosion (changes in frequency of genotypes over time) can result in evolution. Evolution is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).

Incorporating evolutionary thinking into all aspects of biology education can increase student understanding of the concepts of phylogeny as well as evolution. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence supporting evolution increased students' understanding of evolution in a college-level biology course. To find out more about how to teach about evolution, see The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species and studying living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of the changing environment. The changes that occur are often visible.

It wasn't until late 1980s that biologists began to realize that natural selection was at work. The key is the fact that different traits can confer a different rate of survival as well as reproduction, and may be passed on from one generation to another.

In the past, if a certain allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it could be more prevalent than any other allele. As time passes, that could mean that the number of black moths within 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 evolution when the species, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. Samples of each population have been taken frequently and more than 50,000 generations of E.coli have passed.

Lenski's research has revealed that a mutation can dramatically alter the efficiency with which a population reproduces--and so, the rate at which it changes. It also shows that evolution takes time--a fact that many find hard to accept.

Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides have been used. This is because pesticides cause an enticement that favors those who have resistant genotypes.

The speed at which evolution can take place has led to an increasing awareness of its significance in a world shaped by human activities, including climate changes, pollution and the loss of habitats that hinder the species from adapting. Understanding evolution will help us make better choices about the future of our planet and the life of its inhabitants.