The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been for a long time involved in helping those interested in science understand the theory of evolution and how it permeates all areas of scientific exploration.
This site provides students, teachers and general readers with a wide range of learning resources about evolution. It includes the most important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of life. It is used in many cultures and spiritual beliefs as a symbol of unity and love. It has numerous practical applications as well, such as providing a framework to understand the history of species, and how they react to changes in environmental conditions.
Early attempts to describe the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which depend on the sampling of different parts of organisms or fragments of DNA have significantly increased the diversity of a tree of Life2. These trees are mostly populated by eukaryotes and bacterial diversity is vastly underrepresented3,4.
By avoiding the need for direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a more precise way. We can construct trees using molecular techniques like the small-subunit ribosomal gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially true for microorganisms that are difficult to cultivate and which are usually only found in one sample5. A recent analysis of all genomes that are known has created a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and which are not well understood.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats require special protection. This information can be used in many ways, including finding new drugs, battling diseases and improving the quality of crops. The information is also incredibly valuable to conservation efforts. It can help biologists identify the areas most likely to contain cryptic species with potentially important metabolic functions that could be vulnerable to anthropogenic change. Although funds to safeguard biodiversity are vital however, the most effective method to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationships between taxonomic groups. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits could be analogous, or homologous. Homologous traits share their underlying evolutionary path while analogous traits appear like they do, but don't have the same origins. Scientists group similar traits into a grouping referred to as a the clade. All members of a clade share a characteristic, like amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting the clades to determine the organisms that are most closely related to each other.
For a more detailed and precise phylogenetic tree scientists use molecular data from DNA or RNA to determine the relationships among organisms. This data is more precise than morphological information and provides evidence of the evolutionary history of an individual or group. Researchers can utilize Molecular Data to determine the evolutionary age of organisms and identify how many species share the same ancestor.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic flexibility, a type of behavior that alters in response to specific environmental conditions. This can cause a characteristic to appear more resembling to one species than another and obscure the phylogenetic signals. This problem can be addressed by using cladistics, which incorporates a combination of analogous and homologous features in the tree.
In addition, phylogenetics helps predict the duration and rate at which speciation occurs. This information can help conservation biologists decide the species they should safeguard from extinction. In the end, it is the conservation of phylogenetic variety that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The main idea behind evolution is that organisms acquire various characteristics over time as a result of their interactions with their surroundings. A variety of theories about evolution have been developed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed on to offspring.
In the 1930s and 1940s, concepts from a variety of fields -- including natural selection, genetics, and particulate inheritance - came together to create the modern evolutionary theory which explains how evolution occurs through 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 modern evolutionary biology and is mathematically described.
Recent discoveries in evolutionary developmental biology have revealed how variation can be introduced to a species by genetic drift, mutations, reshuffling genes during sexual reproduction and migration between populations. 바카라 에볼루션 , along with others, such as the directional selection process and the erosion of genes (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time, as well as changes in the phenotype (the expression of genotypes in individuals).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. In a study by Grunspan and colleagues. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. To learn more about how to teach about evolution, please see The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of 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 distant event; it is an ongoing process that continues to be observed today. Bacteria mutate and resist antibiotics, viruses evolve and elude new medications and animals change their behavior to the changing environment. The changes that result are often visible.
However, it wasn't until late 1980s that biologists realized that natural selection could be seen in action, as well. The main reason is that different traits can confer the ability to survive at different rates and reproduction, and can be passed down from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour was present in a population of organisms that interbred, it could be more prevalent than any other allele. In time, this could mean the number of black moths in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is much easier when a species has a rapid turnover of its generation such as bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples from each population are taken regularly and over 500.000 generations have been observed.
Lenski's research has demonstrated that mutations can alter the rate of change and the rate of a population's reproduction. It also shows that evolution takes time--a fact that some people find hard to accept.
Another example of microevolution is the way mosquito genes for resistance to pesticides appear more frequently in areas where insecticides are used. That's because the use of pesticides creates a pressure that favors people who have resistant genotypes.
The speed of evolution taking place has led to an increasing recognition of its importance in a world that is shaped by human activity--including climate changes, pollution and the loss of habitats that hinder many species from adjusting. Understanding the evolution process can help you make better decisions about the future of the planet and its inhabitants.