The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science to understand evolution theory and how it is permeated across all areas of scientific research.
This site provides students, teachers and general readers with a variety of learning resources on evolution. It also includes important video clips from NOVA and WGBH produced 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, such as providing a framework for understanding the history of species and how they respond to changes in the environment.
The first attempts at depicting the world of biology focused on the classification of organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods, which are based on the sampling of different parts of organisms, or DNA fragments have significantly increased the diversity of a tree of Life2. However, these trees are largely composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding 에볼루션바카라사이트 for direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. Particularly, molecular techniques allow us to build trees by using sequenced markers, 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 particularly true for microorganisms that are difficult to cultivate and which are usually only found in one sample5. A recent analysis of all genomes known to date has created a rough draft of the Tree of Life, including a large number of archaea and bacteria that are not isolated and which are not well understood.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if specific habitats require special protection. This information can be used in a range of ways, from identifying new remedies to fight diseases to enhancing the quality of the quality of crops. The information is also beneficial to conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species with potentially significant metabolic functions that could be vulnerable to anthropogenic change. While funds to safeguard biodiversity are vital, ultimately the best way to preserve the world's biodiversity is for more people living 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, shows the connections between different groups of organisms. By using molecular information as well as morphological similarities and distinctions or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree that illustrates the evolutionary relationship between taxonomic categories. Phylogeny is essential in understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits are either homologous or analogous. Homologous traits share their evolutionary roots while analogous traits appear similar but do not have the identical origins. Scientists group similar traits into a grouping called a Clade. All members of a clade have a common characteristic, for example, amniotic egg production. They all evolved from an ancestor that had these eggs. A phylogenetic tree can be built by connecting the clades to determine the organisms that are most closely related to each other.
For a more detailed and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to establish the relationships among organisms. This information is more precise and gives evidence of the evolution of an organism. Researchers can utilize Molecular Data to determine the evolutionary age of organisms and determine the number of organisms that have a common ancestor.
The phylogenetic relationships between species can be affected by a variety of factors including phenotypic plasticity, a type of behavior that changes in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than another and obscure the phylogenetic signals. However, this problem can be solved through the use of methods such as cladistics which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics aids determine the duration and rate of speciation. This information can assist conservation biologists in making choices about which species to safeguard from disappearance. Ultimately, it is the preservation of phylogenetic diversity which will result in a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop distinct characteristics over time due to their interactions with their environments. 에볼루션바카라사이트 of evolutionary change have been developed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy 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, theories from various areas, including genetics, natural selection and particulate inheritance, merged to form a contemporary synthesis of evolution theory. This describes how evolution happens through the variation in genes within a population and how these variations alter over time due to natural selection. This model, which encompasses mutations, genetic drift in gene flow, and sexual selection can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variations can be introduced into a species via genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also through the movement of populations. 에볼루션바카라사이트 , along with others like directional selection and 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 over time (the expression of the genotype in an individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking throughout all aspects of biology. A recent study by Grunspan and colleagues, for instance revealed that teaching students about the evidence for evolution increased students' acceptance of evolution in a college-level biology class. For more information about how to teach evolution, see The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a past event; it is an ongoing process that continues to be observed today. Bacteria mutate and resist antibiotics, viruses evolve and are able to evade new medications and animals alter their behavior to the changing environment. The results are often visible.
It wasn't until the late 1980s that biologists began to realize that natural selection was at work. The key is the fact 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 an allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it might become more common than other allele. In time, this could mean that the number of moths that have black pigmentation 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 particular species has a rapid turnover of its generation like bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from one strain. The samples of each population have been taken regularly, and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that mutations can drastically alter the speed at which a population reproduces and, consequently, the rate at which it alters. It also shows that evolution is slow-moving, a fact that some people find difficult to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in populations where insecticides are used. That's because the use of pesticides creates a selective pressure that favors those who have resistant genotypes.
The speed at which evolution takes place has led to an increasing recognition of its importance in a world shaped by human activity--including climate change, pollution and the loss of habitats which prevent the species from adapting. Understanding evolution can help us make better decisions about the future of our planet, as well as the life of its inhabitants.