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The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies have long been involved in helping those interested in science understand the concept of evolution and how it affects every area of scientific inquiry.

This site provides a wide range of sources for students, teachers and general readers of evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.

Tree of Life

The Tree of Life is an ancient symbol that represents 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 respond to changes in environmental conditions.

Early approaches to depicting the world of biology focused on separating organisms into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, based on the sampling of different parts of living organisms, or short fragments of their DNA significantly expanded the diversity that could be included in the tree of life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity remains vastly underrepresented3,4.

Genetic techniques have greatly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods allow us to build trees by using sequenced markers such as the small subunit ribosomal RNA gene.

Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly relevant to microorganisms that are difficult to cultivate and which are usually only found in a single specimen5. A recent analysis of all genomes resulted in an unfinished draft of the Tree of Life. This includes a large number of bacteria, archaea and other organisms that have not yet been isolated or whose diversity has not been well understood6.

This expanded Tree of Life is particularly useful for 에볼루션 사이트 assessing the biodiversity of an area, assisting to determine if specific habitats require special protection. The information is useful in many ways, including finding new drugs, fighting diseases and improving the quality of crops. The information is also incredibly useful to conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with significant metabolic functions that could be at risk from anthropogenic change. While funds to protect biodiversity are important, the best way to conserve the biodiversity of the world is to equip more people in developing nations with the knowledge they need to act locally and support conservation.

Phylogeny

A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. Scientists can create a phylogenetic chart that shows the evolutionary relationships between taxonomic groups based on molecular data and morphological similarities or differences. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that have evolved from common ancestral. These shared traits could be either analogous or homologous. Homologous traits are the same in their evolutionary journey. Analogous traits might appear like they are but they don't have the same origins. Scientists arrange 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 derived from an ancestor that had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the organisms that are most closely related to one another.

Scientists use DNA or RNA molecular data to build a phylogenetic chart which is more precise and 에볼루션 바카라 무료체험게이밍 (mouse click the following post) detailed. This information is more precise and gives evidence of the evolutionary history of an organism. The analysis of molecular data can help researchers determine the number of organisms that have an ancestor common to them and estimate their evolutionary age.

The phylogenetic relationship can be affected by a number of factors, including the phenomenon of phenotypicplasticity. This is a type of behaviour that can change as a result of unique environmental conditions. This can cause a trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics that incorporate a combination of analogous and homologous features into the tree.

In addition, phylogenetics can help predict the duration and 에볼루션 사이트 rate of speciation. This information will assist conservation biologists in deciding which species to safeguard from the threat of extinction. In the end, it's the conservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.

Evolutionary Theory

The main idea behind evolution is that organisms acquire different features over time as a result of their interactions with their environments. A variety of theories about evolution have been proposed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its requirements as well as 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 causes changes that can be passed on to offspring.

In the 1930s and 1940s, 에볼루션 사이트 concepts from a variety of fields -- including genetics, natural selection and particulate inheritance -- came together to form the current synthesis of evolutionary theory which explains how evolution is triggered by the variations of genes within a population and how those variants change over time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, 에볼루션 사이트 and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically described.

Recent discoveries in the field of evolutionary developmental biology have shown that genetic variation can be introduced into a species via mutation, genetic drift and reshuffling genes during sexual reproduction, as well as through the movement of populations. These processes, as well as others, such as directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time as well as changes in the phenotype (the expression of genotypes in an individual).

Students can better understand phylogeny by incorporating evolutionary thinking in all areas of biology. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college-level biology course. For more information on how to teach about evolution, see The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Scientists have studied evolution through looking back in the past--analyzing fossils and comparing species. They also observe living organisms. Evolution is not a distant event, but a process that continues today. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior in the wake of a changing world. The changes that occur are often evident.

However, it wasn't until late 1980s that biologists realized that natural selection can be observed in action as well. The key to this is that different traits can confer an individual rate of survival as well as reproduction, and may be passed down from one generation to the next.

In the past when one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding species, it could rapidly become more common than the other alleles. In time, this could mean that the number of moths with black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to observe evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from a single strain. The 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 of change and the rate at which a population reproduces. It also shows that evolution takes time, a fact that some find hard to accept.

Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in populations that have used insecticides. 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 recognition of its importance in a world shaped by human activity, including climate change, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution will aid you in making better decisions about the future of the planet and its inhabitants.