The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies have been for a long time involved in helping people who are interested in science understand the theory of evolution and how it affects all areas of scientific research.

This site provides teachers, students and general readers with a range of learning resources on evolution. It contains important video clips from NOVA and WGBH's science programs on DVD.

Tree of Life

The Tree of Life, [Redirect Only] an ancient symbol, represents the interconnectedness of all life. It is a symbol of love and unity in many cultures. It also has important practical uses, like providing a framework for understanding the history of species and how they respond to changes in environmental conditions.

Early attempts to represent the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on the collection of various parts of organisms or short DNA fragments have greatly increased the diversity of a Tree of Life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.

By avoiding the necessity for 에볼루션 바카라 무료체험 - click the following document - direct observation and experimentation, genetic techniques have allowed us to depict the Tree of Life in a more precise manner. Particularly, molecular techniques allow us to construct trees by using sequenced markers, 무료 에볼루션 such as the small subunit ribosomal RNA gene.

The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is especially true of microorganisms that are difficult to cultivate and are usually only represented in a single sample5. Recent analysis of all genomes resulted in an initial draft of a Tree of Life. This includes a large number of archaea, bacteria and other organisms that haven't yet been identified or their diversity is not well understood6.

This expanded Tree of Life can be used to evaluate the biodiversity of a particular area and determine if particular habitats need special protection. This information can be used in a range of ways, from identifying the most effective remedies to fight diseases to enhancing crop yields. The information is also beneficial in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. Although funds to safeguard biodiversity are vital but the most effective way to protect 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 relationships between groups of 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 phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and have evolved from a common ancestor. These shared traits may be analogous, or homologous. Homologous traits are identical in their evolutionary origins, while analogous traits look like they do, but don't have the identical origins. Scientists combine similar traits into a grouping referred to as a Clade. For instance, all the species in a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor 에볼루션 슬롯게임 (Http://www.kuniunet.com/Home.php?Mod=space&uid=1554454) who had these eggs. The clades are then linked to form a phylogenetic branch to determine the organisms with the closest connection to each other.

Scientists use DNA or RNA molecular information to build a phylogenetic chart that is more accurate and detailed. This information is more precise and gives evidence of the evolution of an organism. Researchers can use Molecular Data to estimate the evolutionary age of organisms and determine the number of organisms that have a common ancestor.

The phylogenetic relationship can be affected by a variety of factors that include the phenomenon of phenotypicplasticity. This is a type of behavior that alters as a result of unique environmental conditions. This can cause a trait to appear more similar to one species than to another which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a the combination of analogous and homologous features in the tree.

In addition, phylogenetics helps determine the duration and rate at which speciation occurs. This information can aid conservation biologists in making decisions about which species to save 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 central theme of evolution is that organisms develop distinct characteristics over time as a result of their interactions with their environment. Many theories of evolution have been proposed by a wide range of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that could be passed onto offspring.

In the 1930s & 1940s, theories from various areas, including genetics, natural selection and particulate inheritance, came together to create a modern theorizing of evolution. This explains how evolution occurs by the variation of genes in the population, and how these variations alter over time due to natural selection. This model, which encompasses mutations, genetic drift as well as gene flow and sexual selection is mathematically described mathematically.

Recent discoveries in evolutionary developmental biology have revealed the ways in which variation can be introduced to a species by genetic drift, mutations and reshuffling of genes during sexual reproduction and the movement between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of a genotype over time) can result in evolution that is defined as changes in the genome of the species over time, and also by changes 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 in all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance revealed that teaching students about the evidence for evolution helped students accept the concept of evolution in a college-level biology class. For more details on how to teach about evolution read The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

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

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

In the past when one particular allele - the genetic sequence that determines coloration--appeared in a population of interbreeding organisms, it might quickly become more prevalent than the other alleles. Over time, that would mean 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.

The ability to observe evolutionary change is much easier when a species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples of each population were taken regularly, and more than 50,000 generations of E.coli have passed.

Lenski's work has demonstrated that a mutation can dramatically alter the efficiency with which a population reproduces--and so, the rate at which it alters. It also demonstrates that evolution takes time, which is difficult for some to accept.

Another example of microevolution is the way mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are employed. This is due to pesticides causing an exclusive pressure that favors individuals who have resistant genotypes.

The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution can help us make better choices about the future of our planet, as well as the lives of its inhabitants.