The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are committed to helping those interested in science to understand evolution theory and how it is permeated in all areas of scientific research.
This site provides teachers, students and general readers with a wide range of learning resources on evolution. It contains the most important 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 used in many religions and cultures as an emblem of unity and love. It has many practical applications as well, such as providing a framework to understand the history of species and how they respond to changing environmental conditions.
The earliest attempts to depict the biological world focused on categorizing species into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, which are based on the sampling of different parts of organisms or short DNA fragments, have greatly increased the diversity of a tree of Life2. These trees are largely composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.
By avoiding the necessity for direct experimentation and observation genetic techniques have allowed us to represent the Tree of Life in a more precise manner. Trees can be constructed using molecular techniques such as the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much diversity to be discovered. This is particularly the case for microorganisms which are difficult to cultivate and are usually found in a single specimen5. A recent study of all genomes that are known has produced a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and whose diversity is poorly understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if specific habitats require protection. The information can be used in a range of ways, from identifying new treatments to fight disease to enhancing the quality of crops. It is also beneficial in conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with important metabolic functions that could be at risk from anthropogenic change. While funds to protect biodiversity are important, the most effective method to protect the biodiversity of the world is to equip the people of developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between groups of organisms. By using molecular information, morphological similarities and differences or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits can be either analogous or homologous. Homologous traits are identical in their evolutionary origins and analogous traits appear like they do, but don't have the same origins. Scientists arrange similar traits into a grouping called a clade. All members of a clade share a characteristic, for example, amniotic egg production. They all evolved from an ancestor with these eggs. The clades then join to form a phylogenetic branch to identify organisms that have the closest connection to each other.
For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to determine the relationships between organisms. This information is more precise than morphological information and gives evidence of the evolutionary history of an organism or group. Researchers can utilize Molecular Data to estimate the evolutionary age of organisms and determine how many organisms have the same ancestor.
Phylogenetic relationships can be affected by a number of factors that include phenotypicplasticity. This is a kind of behaviour that can change as a result of unique environmental conditions. This can cause a characteristic to appear more resembling to one species than to another and obscure the phylogenetic signals. However, this issue can be cured by the use of methods such as cladistics which incorporate a combination of homologous and analogous features into the tree.
Furthermore, phylogenetics may aid in predicting the length and speed of speciation. This information can help conservation biologists decide which species they should protect from the threat of extinction. In the end, it is the conservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
original site in evolution is that organisms change 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 a living thing would develop according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived 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, ideas from various fields, including natural selection, genetics, and particulate inheritance - came together to form the modern evolutionary theory that explains how evolution is triggered by the variations of genes within a population, and how those 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 is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species through mutation, genetic drift and reshuffling of genes during sexual reproduction, as well as through migration between populations. These processes, in conjunction with others, such as directional selection and gene erosion (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time and changes in phenotype (the expression of genotypes in individuals).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny as well as evolution. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence supporting evolution increased students' acceptance of evolution in a college-level biology class. For more information on how to teach about evolution look up The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily as 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 is not a past moment; it is an ongoing process. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications, and animals adapt their behavior to the changing environment. The results are often apparent.
It wasn't until late 1980s that biologists began realize that natural selection was in play. The key is that different traits confer different rates of survival and reproduction (differential fitness) and can be transferred from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour - appeared in a population of organisms that interbred, it could become more prevalent than any other allele. 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 evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples from each population are taken on a regular basis, and over fifty thousand generations have been observed.
Lenski's research has shown that mutations can drastically alter the efficiency with which a population reproduces--and so, the rate at which it evolves. 에볼루션 바카라 무료체험 demonstrates that evolution takes time, a fact that is hard for some to accept.
Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides have been used. Pesticides create an exclusive pressure that favors individuals who have resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing appreciation of its importance in a world shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process will help us make better decisions about the future of our planet and the life of its inhabitants.