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The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies are committed to helping those interested in science understand evolution theory and how it is permeated throughout all fields of scientific research.

This site provides teachers, students and general readers with a variety of learning resources about evolution. It includes the most important 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 is seen in a variety of religions and cultures as an emblem of unity and love. It also has practical applications, like providing a framework to understand the history of species and how they react to changes in the environment.

Early approaches to depicting the world of biology focused on the classification of species into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods rely on the sampling of different parts of organisms, or DNA fragments have significantly increased the diversity of a Tree of Life2. The trees are mostly composed by eukaryotes and the diversity of bacterial species is greatly underrepresented3,4.

In avoiding the necessity of direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. Particularly, molecular methods allow us to build trees by using sequenced markers like the small subunit of ribosomal RNA gene.

The Tree of Life has been significantly expanded by genome sequencing. However there is still a lot of biodiversity to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are usually only present in a single sample5. Recent analysis of all genomes produced an unfinished draft of a Tree of Life. This includes a large number of archaea, bacteria and other organisms that haven't yet been isolated or whose diversity has not been fully understood6.

This expanded Tree of Life can be used to determine the diversity of a particular area and determine if certain habitats require special protection. The information is useful in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. The information is also useful to conservation efforts. It can aid biologists in identifying areas that are most likely to have cryptic species, which may have vital metabolic functions and are susceptible to human-induced change. Although funding to safeguard biodiversity are vital however, the most effective method to preserve the world's biodiversity is for more people in developing countries to be empowered with the knowledge to act locally in order to promote conservation from within.

Phylogeny

A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. Using molecular data similarities and differences in morphology or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. Phylogeny is essential in understanding the evolution of biodiversity, evolution and genetics.

A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and evolved from an ancestor with common traits. These shared traits are either analogous or homologous. Homologous traits share their evolutionary origins and analogous traits appear similar, but do not share the same ancestors. Scientists group similar traits into a grouping referred to as a 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 eggs. The clades then join to form a phylogenetic branch that can determine the organisms with the closest connection to each other.

To create a more thorough and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and provides evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to determine the age of evolution of organisms and identify the number of organisms that have a common ancestor.

The phylogenetic relationships of organisms can be affected by a variety of factors including phenotypic plasticity, a type of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to a species than to another which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a a combination of homologous and analogous features in the tree.

Furthermore, phylogenetics may help predict the duration and rate of speciation. This information can assist conservation biologists in deciding which species to safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.

Evolutionary Theory

The main idea behind evolution is that organisms change over time due to their interactions with their environment. Many theories of evolution have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits can cause changes that can be passed on to offspring.

In the 1930s and 1940s, ideas from various fields, 에볼루션 바카라 카지노 사이트 (bbs.worldsu.org) including natural selection, genetics, and particulate inheritance - came together to form the current synthesis of evolutionary theory that explains how evolution is triggered by the variation of genes within a population and how those variations change over time due to natural selection. This model, which incorporates mutations, genetic drift, gene flow and sexual selection, can be mathematically described mathematically.

Recent developments in the field of evolutionary developmental biology have demonstrated how variations can be introduced to a species via genetic drift, mutations and reshuffling of genes during sexual reproduction and the movement between populations. These processes, as well as others such as directional selection or 에볼루션 슬롯 genetic erosion (changes in the frequency of the genotype over time) can lead to evolution that is defined as change in the genome of the species over time, and 에볼루션사이트 the change in phenotype as time passes (the expression of that genotype in an individual).

Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college biology course. For more information on how to teach about evolution, please look up 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 through studying fossils, comparing species and observing living organisms. However, evolution isn't something that happened in the past; it's an ongoing process taking place today. Bacteria mutate and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals change their behavior to a changing planet. The resulting changes are often visible.

But it wasn't until the late 1980s that biologists realized that natural selection could 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 another.

In the past, if one particular allele, the genetic sequence that defines color in a group of interbreeding organisms, it might quickly become more prevalent than other alleles. Over time, this would mean that the number of moths sporting black pigmentation may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to see evolution when a species, such as 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 from each population have been taken regularly and more than 500.000 generations of E.coli have been observed to have passed.

Lenski's research has shown that mutations can drastically alter the rate at the rate at which a population reproduces, and consequently the rate at which it evolves. It also demonstrates that evolution takes time, a fact that is hard for some to accept.

Another example of microevolution is that mosquito genes that confer resistance to pesticides show up more often in populations where insecticides are employed. This is due to pesticides causing a selective pressure which favors those who have resistant genotypes.

The rapid pace at which evolution takes place has led to a growing recognition of its importance in a world shaped by human activity--including climate change, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution can assist you in making better choices regarding the future of the planet and its inhabitants.