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The Academy's Evolution Site

Biology is a key 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 affects every area of scientific inquiry.

This site provides teachers, students and general readers with a variety of learning resources about evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.

Tree of Life

The Tree of Life, 에볼루션 블랙잭 an ancient symbol, symbolizes the interconnectedness of all life. It is used in many spiritual traditions and cultures as an emblem of unity and love. It also has practical uses, like providing a framework to understand the evolution of species and how they respond to changing environmental conditions.

The first attempts at depicting the world of biology focused on the classification of organisms into distinct categories that were distinguished by physical and metabolic characteristics1. These methods, based on the sampling of various parts of living organisms, or sequences of short fragments of their DNA, greatly increased the variety of organisms that could be represented in the tree of life2. These trees are mostly populated of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.

By avoiding the necessity for direct experimentation and observation, genetic techniques have enabled us to represent the Tree of Life in a much more accurate way. In particular, molecular methods allow us to build trees by using sequenced markers such as the small subunit of ribosomal RNA gene.

Despite the dramatic expansion of the Tree of Life through genome sequencing, a lot of biodiversity remains to be discovered. This is especially the case for microorganisms which are difficult to cultivate, and which are usually only found in a single specimen5. A recent analysis of all genomes that are known has produced a rough draft version of the Tree of Life, including many archaea and bacteria that are not isolated and whose diversity is poorly understood6.

This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require special protection. The information can be used in a range of ways, from identifying the most effective remedies to fight diseases to improving crop yields. The information is also incredibly beneficial for conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with important metabolic functions that may be at risk of anthropogenic changes. While funds to protect biodiversity are crucial, ultimately the best way to ensure the preservation of biodiversity around the world is for more people in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Scientists can construct a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic groups based on molecular data and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestors. These shared traits could be either homologous or analogous. Homologous traits are identical in their evolutionary roots, while analogous traits look similar but do not have the same ancestors. Scientists combine similar traits into a grouping referred to as a Clade. All organisms in a group share a characteristic, for example, amniotic egg production. They all derived from an ancestor with these eggs. The clades are then connected to form a phylogenetic branch to determine the organisms with the closest relationship.

For a more detailed and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the relationships among organisms. This information is more precise than morphological data and gives evidence of the evolutionary history of an organism or group. Molecular data allows researchers to identify the number of species that have an ancestor common to them and estimate their evolutionary age.

The phylogenetic relationships between species can be influenced by several factors, including phenotypic flexibility, a type of behavior that changes in response to unique environmental conditions. This can cause a particular trait to appear more similar in one species than another, clouding the phylogenetic signal. This issue can be cured by using cladistics. This is a method that incorporates a combination of homologous and analogous features in the tree.

In addition, phylogenetics can aid in predicting the length and speed of speciation. This information can help conservation biologists make decisions about which species they should protect from the threat of extinction. In the end, it's the conservation of phylogenetic diversity which will create an ecosystem that is complete and 에볼루션 룰렛 에볼루션 바카라 사이트 [click through the next article] balanced.

Evolutionary Theory

The central theme in evolution is that organisms alter over time because of their interactions with their environment. Several theories of evolutionary change have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to the offspring.

In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This defines how evolution happens through the variations in genes within the population, and how these variants alter over time due to natural selection. This model, known as genetic drift or 에볼루션 블랙잭; linked here, mutation, gene flow and sexual selection, is a key element of modern evolutionary biology and 에볼루션 블랙잭 can be mathematically explained.

Recent developments in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species via mutation, genetic drift, and reshuffling of genes during sexual reproduction, as well as through migration between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution which is defined by change in the genome of the species over time and also by changes in phenotype as time passes (the expression of the genotype within the individual).

Students can better understand phylogeny by incorporating evolutionary thinking throughout all areas of biology. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence that supports evolution increased students' understanding of evolution in a college-level biology class. For more information on how to teach about evolution, 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 looked at evolution through the past--analyzing fossils and comparing species. They also observe living organisms. But evolution isn't just something that happened in the past. It's an ongoing process that is happening today. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior because of a changing world. The resulting changes are often easy to see.

But it wasn't until the late-1980s that biologists realized that natural selection can be observed in action as well. The key is that various characteristics result in different rates of survival and reproduction (differential fitness) and are passed from one generation to the next.

In the past, if one allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could become more common than other allele. Over time, this would mean that the number of moths that have black pigmentation in a group may 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 easier when a particular species has a rapid turnover of its generation like bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from one strain. Samples of each population have been taken frequently and more than 50,000 generations of E.coli have been observed to have passed.

Lenski's work has shown that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time, a fact that some people find difficult to accept.

Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides are used. This is because pesticides cause a selective pressure which favors those with resistant genotypes.

The speed at which evolution takes place has led to an increasing appreciation of its importance in a world that is shaped by human activity--including climate change, pollution, and the loss of habitats that prevent many species from adapting. Understanding evolution can help us make smarter decisions regarding the future of our planet and the lives of its inhabitants.