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The Academy's Evolution Site
Biological evolution is one of the most fundamental concepts in biology. The Academies have been active for a long time in helping people who are interested in science comprehend 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 about evolution. It includes 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 an emblem of love and harmony in a variety of cultures. It has numerous practical applications as well, including providing a framework to understand the evolution of species and how they react to changing environmental conditions.
Early attempts to describe the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on the sampling of different parts of living organisms or on sequences of small fragments of their DNA, significantly expanded the diversity that could be included in a tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
Genetic techniques have greatly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. 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 greatly expanded thanks to genome sequencing. However there is still a lot of diversity to be discovered. This is especially relevant to microorganisms that are difficult to cultivate, and are typically found in one sample5. A recent study of all known genomes has produced a rough draft of the Tree of Life, including many bacteria and archaea that are not isolated and which are not well understood.
This expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if specific habitats need special protection. The information is useful in many ways, including finding new drugs, battling diseases and improving crops. It is also useful to conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species that could have important metabolic functions that may be vulnerable to anthropogenic change. While conservation funds are important, the best method to protect the biodiversity of the world is to equip the people of developing nations with the information they require to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, illustrates the relationships between different groups of organisms. Scientists can construct an phylogenetic chart which shows the evolution of taxonomic groups based on molecular data and morphological similarities or differences. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestors. These shared traits may be analogous or homologous. Homologous traits are similar in their evolutionary origins, while analogous traits look similar but do not have the same origins. Scientists combine similar traits into a grouping known as a Clade. For instance, all of the species in a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor that had eggs. A phylogenetic tree is then built 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 make use of molecular data from DNA or RNA to determine the relationships among organisms. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to calculate the age of evolution of organisms and determine how many species have an ancestor common to all.
The phylogenetic relationships of a species can be affected by a number of factors such as the phenotypic plasticity. This is a type of behavior that changes in response to specific environmental conditions. This can cause a trait to appear more similar to one species than to the other and obscure the phylogenetic signals. This issue can be cured by using cladistics, which incorporates a combination of homologous and analogous traits in the tree.
In addition, phylogenetics helps determine the duration and rate of speciation. This information can help conservation biologists decide which species they should protect from extinction. In the end, it is the conservation of phylogenetic variety which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme of evolution is that organisms develop distinct characteristics over time due to their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could develop according to its own requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can lead to changes that are passed on to the
In the 1930s and 1940s, theories from various fields, including natural selection, genetics, and particulate inheritance - came together to form the modern evolutionary theory synthesis, which defines how evolution is triggered by the variation of genes within a population and how these variants change in time due to natural selection. This model, which includes 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 by genetic drift, mutation, and reshuffling genes during sexual reproduction, as well as by migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of the genotype over time) can result in 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 the individual).
Incorporating evolutionary thinking into all areas of biology education could increase students' understanding of phylogeny as well as evolution. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution increased students' acceptance of evolution in a college biology course. To find out more about how to teach about evolution, look up The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by studying fossils, comparing species and studying living organisms. Evolution isn't a flims event, but a process that continues today. Bacteria evolve and resist antibiotics, viruses re-invent themselves and escape new drugs and animals change their behavior in response to a changing planet. The changes that occur are often visible.
It wasn't until the late 1980s that biologists began to realize that natural selection was in action. The key is that different traits have different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it could become more common than other allele. As time passes, this could mean that the number of moths that have 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 observe evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples of each are taken every day, and over 500.000 generations have passed.
Lenski's research has shown that a mutation can profoundly alter the efficiency with the rate at which a population reproduces, and consequently the rate at which it evolves. It also shows that evolution takes time, a fact that some people find difficult to accept.
Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more common in populations where insecticides have been used. Pesticides create a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world shaped largely by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding 에볼루션바카라사이트 can assist you in making better choices about the future of our planet and its inhabitants.