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The Academy's Evolution Site

Biology is one of the most central concepts in biology. The Academies are committed to helping those who are interested in science comprehend the evolution theory and how it is permeated throughout all fields of scientific research.

This site provides a wide range of sources for teachers, students as well as general readers about evolution. It includes key video clips from NOVA and the WGBH-produced science programs on DVD.

Tree of Life

The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is an emblem of love and harmony in a variety of cultures. It has numerous practical applications as well, such as providing a framework to understand the history of species and how they react to changes in environmental conditions.

Early approaches to depicting the biological world focused on the classification of organisms into distinct categories which were distinguished by their physical and metabolic characteristics1. These methods, which are based on the sampling of different parts of organisms or short fragments of DNA, have greatly increased the diversity of a Tree of Life2. However the trees are mostly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.

Genetic techniques have greatly broadened our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular methods allow us to construct trees by using sequenced markers, such as the small subunit ribosomal gene.

The Tree of Life has been significantly expanded by genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true for microorganisms, which are difficult to cultivate and are typically only present in a single sample5. A recent analysis of all genomes that are known has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated and their diversity is not fully understood6.

The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, assisting to determine if certain habitats require special protection. This information can be utilized in a variety of ways, including identifying new drugs, combating diseases and enhancing crops. This information is also useful in conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species that could have important metabolic functions that could be at risk from anthropogenic change. Although funding to protect biodiversity are essential but the most effective way to preserve the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) illustrates the relationship between organisms. Utilizing molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree which illustrates the evolution of taxonomic categories. Phylogeny plays a crucial role in understanding the relationship between genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestral. These shared traits could be analogous or homologous. Homologous traits share their underlying evolutionary path and analogous traits appear similar but do not have the identical origins. Scientists group similar traits into a grouping known as a the clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor which had these eggs. A phylogenetic tree is then constructed by connecting the clades to determine the organisms which are the closest to one another.

For a more precise and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the connections between organisms. This information is more precise and gives evidence of the evolution of an organism. The use of molecular data lets researchers determine the number of organisms who share the same ancestor and estimate their evolutionary age.

The phylogenetic relationships of a species can be affected by a variety of factors, 에볼루션 바카라 사이트 including the phenomenon of phenotypicplasticity. This is a type behavior that alters as a result of unique 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 cured by the use of methods such as cladistics that incorporate a combination of similar and homologous traits into the tree.

Additionally, phylogenetics can help determine the duration and speed at which speciation takes place. This information can assist conservation biologists make decisions about which species to protect from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.

Evolutionary Theory

The central theme of evolution is that organisms develop distinct characteristics over time based on their interactions with their environment. Many theories of evolution have been developed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that could be passed on to offspring.

In the 1930s and 1940s, 에볼루션 게이밍에볼루션 바카라 체험사이트, http://lzdsxxb.com/home.php?mod=space&uid=3713547, theories from various fields, including natural selection, genetics & particulate inheritance, merged to form a contemporary theorizing of evolution. This defines how evolution happens through the variation in genes within the population and how these variations change with time due to natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is a key element of modern evolutionary biology and can be mathematically explained.

Recent discoveries in evolutionary developmental biology have revealed how variation can be introduced to a species via genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, as well as 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 the change in phenotype as time passes (the expression of that genotype in the individual).

Incorporating evolutionary thinking into all aspects of biology education can improve students' understanding of phylogeny as well as evolution. In a recent study conducted by Grunspan and colleagues. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during the course of a college biology. For more details on how to teach evolution look up The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution through looking back, studying fossils, comparing species, and observing living organisms. Evolution is not a past event; it is an ongoing process. Viruses evolve to stay away from new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The changes that occur are often visible.

However, it wasn't until late 1980s that biologists understood that natural selection could be seen in action, as well. The reason is that different traits have different rates of survival and reproduction (differential fitness), and can be passed down from one generation to the next.

In the past, when one particular allele - the genetic sequence that controls coloration - was present in a population of interbreeding organisms, it might rapidly become more common than the other alleles. In time, this could mean that the number of moths with black pigmentation 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 much easier when a species has a rapid generation turnover, as with bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples of each population are taken every day and over fifty thousand generations have been observed.

Lenski's research has shown that a mutation can dramatically alter the rate at which a population reproduces and, consequently the rate at which it alters. It also shows that evolution takes time, which is hard for some to accept.

Another example of microevolution is that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are used. This is because the use of pesticides causes a selective pressure that favors individuals who have resistant genotypes.

The speed at which evolution can take place has led to an increasing recognition of its importance in a world that is shaped by human activities, including climate change, pollution and the loss of habitats that prevent many species from adjusting. Understanding evolution will help us make better choices about the future of our planet, and the life of its inhabitants.