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The Academy's Evolution Site

Biological evolution is one of the most central concepts in biology. The Academies have long been involved in helping those interested in science understand the concept of evolution and how it influences every area of scientific inquiry.

This site provides a range of resources for students, teachers as well as general readers about evolution. It has key video clips from NOVA and WGBH's science programs on DVD.

Tree of Life

The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is a symbol of love and unity across many cultures. It also has many practical applications, like providing a framework to understand the evolution 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 had been distinguished by their physical and metabolic characteristics1. These methods, which are based on the collection of various parts of organisms, or DNA fragments, have significantly increased the diversity of a tree of Life2. These trees are mostly populated of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.

In avoiding the necessity of direct experimentation and observation genetic techniques have allowed us to represent the Tree of Life in a more precise way. Trees can be constructed by using molecular methods, such as the small-subunit ribosomal gene.

Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is especially the case for microorganisms which are difficult to cultivate, and are typically present in a single sample5. A recent study of all known genomes has produced a rough draft version of the Tree of Life, including many archaea and bacteria that are not isolated and whose diversity is poorly understood6.

This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, which can help to determine if certain habitats require protection. The information is useful in a variety of ways, including finding new drugs, battling diseases and improving crops. This information is also extremely valuable to conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with important metabolic functions that could be vulnerable to anthropogenic change. Although funding to safeguard biodiversity are vital however, the most effective method to ensure the preservation of biodiversity around the world is for more people in developing countries to be empowered with the knowledge to act locally to promote conservation from within.

Phylogeny

A phylogeny is also known as an evolutionary tree, illustrates the connections between groups of organisms. By using molecular information similarities and differences in morphology or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.

A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and evolved from an ancestor with common traits. These shared traits could be either analogous or 에볼루션 바카라사이트 homologous. Homologous traits are the same in terms of their evolutionary journey. Analogous traits could appear like they are however they do not have the same origins. Scientists arrange similar traits into a grouping called a Clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all came from an ancestor 에볼루션 룰렛사이트 [Suggested Online site] who had these eggs. The clades are then connected to create a phylogenetic tree to identify organisms that have the closest relationship.

Scientists utilize molecular DNA or RNA data to build a phylogenetic chart that is more precise and detailed. This information is more precise and gives evidence of the evolution history of an organism. The analysis of molecular data can help researchers determine the number of species that have the same ancestor and estimate their evolutionary age.

The phylogenetic relationships between species can be affected by a variety of factors, including phenotypic flexibility, an aspect of behavior 에볼루션 바카라사이트 that alters in response to specific environmental conditions. This can make a trait appear more resembling to one species than to another which can obscure the phylogenetic signal. This issue can be cured by using cladistics. This is a method that incorporates a combination of homologous and analogous features in the tree.

Additionally, phylogenetics can help determine the duration and 에볼루션 게이밍 speed of speciation. This information can help conservation biologists make decisions about the species they should safeguard from extinction. Ultimately, it is the preservation of phylogenetic diversity that will lead to a complete and balanced ecosystem.

Evolutionary Theory

The fundamental concept of evolution is that organisms develop various characteristics over time as a result of their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would develop according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of traits can cause changes that can be passed on to future generations.

In the 1930s and 1940s, concepts from a variety of fields -- including genetics, natural selection, and particulate inheritance -- came together to create the modern synthesis of evolutionary theory, which defines how evolution occurs through the variations of genes within a population, and how these variants change in time as a result of natural selection. This model, called genetic drift mutation, gene flow and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically described.

Recent developments in the field of evolutionary developmental biology have demonstrated how variation can be introduced to a species by mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution, which is defined by changes in the genome of the species over time and also by changes in phenotype over time (the expression of the genotype in an individual).

Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolution. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution helped students accept the concept of evolution in a college-level biology course. For more details about 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

Scientists have studied evolution by looking in the past, analyzing fossils and comparing species. They also study living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Bacteria transform and resist antibiotics, viruses reinvent themselves and escape new drugs and animals change their behavior in response to the changing climate. The changes that result are often visible.

But it wasn't until the late 1980s that biologists understood that natural selection could be seen in action, as well. The key to this is that different traits result in an individual rate of survival and reproduction, and can be passed on from one generation to the next.

In the past when one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it could quickly become more common than other alleles. In time, this could mean that the number of moths with black pigmentation in a population could increase. 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 species has a rapid turnover of its generation such as bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. Samples of each population have been collected frequently and more than 50,000 generations of E.coli have been observed to have passed.

Lenski's research has demonstrated that mutations can alter the rate of change and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time, something that is hard for some to accept.

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

The rapid pace of evolution taking place has led to an increasing awareness of its significance in a world shaped by human activity--including climate change, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution will help us make better decisions regarding the future of our planet as well as the lives of its inhabitants.