The Academy's Evolution Site
The concept of biological evolution is among the most important 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 influences all areas of scientific research.
This site provides a wide range of sources for students, teachers as well as general readers about evolution. It has 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 an emblem of love and unity in many cultures. It can be used in many practical ways in addition to providing a framework for understanding the history of species, and how they respond to changing environmental conditions.
Early attempts to represent the world of biology 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 short fragments of their DNA, greatly increased the variety of organisms that could be represented in the tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have allowed us to depict the Tree of Life in a more precise manner. Trees can be constructed by using molecular methods such as the small subunit ribosomal gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is particularly true of microorganisms, which are difficult to cultivate and are often only present in a single specimen5. Recent analysis of all genomes has produced an initial draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that haven't yet been isolated or the diversity of which is not thoroughly understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, assisting to determine if certain habitats require protection. This information can be utilized in many ways, including identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely useful to conservation efforts. It helps biologists discover areas most likely to have cryptic species, which may have important metabolic functions, and could be susceptible to the effects of human activity. While funds to protect biodiversity are crucial however, the most effective method to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, reveals the connections between various groups of organisms. Scientists can construct a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic categories using molecular information and morphological differences or similarities. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.
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 homologous, or analogous. Homologous characteristics are identical in their evolutionary path. Analogous traits may look like they are but they don't have the same origins. Scientists organize similar traits into a grouping known as a the clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor who had these eggs. A phylogenetic tree is built by connecting the clades to identify the species that are most closely related to one another.
Scientists make use of DNA or RNA molecular data to build a phylogenetic chart that is more accurate and precise. This information is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. The analysis of molecular data can help researchers determine the number of species who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic flexibility, a type of behavior that alters in response to unique environmental conditions. This can cause a particular trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, 에볼루션 바카라 체험 can be solved through the use of methods such as cladistics that include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics aids determine the duration and speed of speciation. This information can assist conservation biologists decide which species they should protect 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 main idea behind evolution is that organisms acquire various characteristics over time based on their interactions with their surroundings. A variety of theories about evolution have been developed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly in accordance with its needs and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits can cause changes that could be passed on to offspring.
In the 1930s and 1940s, theories from various fields, including natural selection, genetics, and particulate inheritance - came together to form the current synthesis of evolutionary theory which explains how evolution occurs through the variation of genes within a population and how these variants change in time as a result of natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is the foundation of modern evolutionary biology and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also by migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of a genotype over time) can result in evolution which is defined by changes in the genome of the species over time and also the change in phenotype over time (the expression of that genotype in the individual).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking throughout all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance revealed that teaching students about the evidence that supports evolution increased students' understanding of evolution in a college biology course. To learn more about how to teach about evolution, please see The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past, studying fossils, and comparing species. They also observe living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses evolve and are able to evade new medications, and animals adapt their behavior in response to a changing planet. The results are usually visible.
It wasn't until the 1980s that biologists began realize that natural selection was also in action. The key is the fact that different traits result in an individual rate of survival as well as reproduction, and may be passed down from one generation to another.
In the past when one particular allele - the genetic sequence that determines coloration--appeared in a population of interbreeding organisms, it could rapidly become more common than other alleles. Over time, that would mean that the number of black moths within a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Observing evolutionary change in action is much easier when a species has a fast generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. Samples from each population were taken regularly and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has shown that mutations can drastically alter 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 are unable to accept.
Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more prevalent in areas where insecticides are used. This is due to pesticides causing a selective pressure which favors those who have resistant genotypes.
The rapid pace at which evolution takes place has led to a growing awareness of its significance in a world that is shaped by human activity--including climate changes, pollution and the loss of habitats which prevent many species from adjusting. Understanding evolution will help us make better decisions about the future of our planet, and the life of its inhabitants.