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So You've Bought Evolution Site ... Now What?
The Academy's Evolution Site

Biology is one of the most fundamental concepts in biology. The Academies have long been involved in helping those interested in science understand the theory of evolution and how it affects all areas of scientific exploration.

This site offers a variety of sources for teachers, students, and general readers on evolution. It includes 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 used in many religions and cultures as a symbol of unity and love. It has many practical applications in addition to providing a framework to understand the evolution of species and how they respond to changes in environmental conditions.


The first attempts at depicting the world of biology focused on the classification of species into distinct categories that were identified by their physical and metabolic characteristics1. These methods depend on the collection of various parts of organisms or short fragments of DNA have greatly increased the diversity of a Tree of Life2. The trees are mostly composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.

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

The Tree of Life has been significantly expanded by genome sequencing. However there is a lot of biodiversity to be discovered. This is especially true for microorganisms that are difficult to cultivate and which are usually only found in a single specimen5. A recent analysis of all genomes that are known has created a rough draft of the Tree of Life, including many bacteria and archaea that have not been isolated, and their diversity is not fully understood6.

The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine if certain habitats require protection. This information can be utilized in a variety of ways, including finding new drugs, fighting diseases and enhancing crops. This information is also extremely useful for conservation efforts. It can aid biologists in identifying areas that are most likely to have species that are cryptic, which could have important metabolic functions and be vulnerable to changes caused by humans. Although funding to protect biodiversity are essential but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be equipped with the knowledge to act locally in order to promote conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Utilizing 무료에볼루션 and distinctions, or ontogeny (the process of the development of an organism), scientists can build a phylogenetic tree that illustrates the evolution of taxonomic categories. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestral. These shared traits could be analogous, or homologous. Homologous traits share their evolutionary origins and analogous traits appear like they do, but don't have the identical origins. Scientists arrange similar traits into a grouping called a the clade. For example, all of the organisms that make up a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor who had these eggs. The clades are then linked to create a phylogenetic tree to determine the organisms with the closest connection to each other.

Scientists use molecular DNA or RNA data to create a phylogenetic chart which is more precise and detailed. This information is more precise and provides evidence of the evolution of an organism. The analysis of molecular data can help researchers identify the number of organisms that have the same ancestor and estimate their evolutionary age.

The phylogenetic relationships of a species can be affected by a number of factors such as the phenotypic plasticity. This is a type behavior that alters as a result of unique environmental conditions. This can cause a characteristic 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 the combination of homologous and analogous traits in the tree.

In addition, phylogenetics can help predict the duration and rate of speciation. This information will assist conservation biologists in making choices about which species to safeguard from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will result in a complete and balanced ecosystem.

Evolutionary Theory

The main idea behind evolution is that organisms acquire different features over time as a result of their interactions with their environment. Many theories of evolution have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its requirements and needs, 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 can cause changes that could be passed on to offspring.

In the 1930s and 1940s, theories from a variety of fields -- including natural selection, genetics, and particulate inheritance - came together to create the modern synthesis of evolutionary theory which explains how evolution is triggered by the variation of genes within a population and how those variants change over time as a result of natural selection. This model, which encompasses mutations, genetic drift, gene flow and sexual selection can be mathematically described.

Recent advances in the field of evolutionary developmental biology have revealed how variations can be introduced to a species by mutations, genetic drift or reshuffling of genes in sexual reproduction, and even 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 by changes in phenotype as time passes (the expression of that genotype in an individual).

Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking throughout all areas of biology. In a recent study conducted by Grunspan et al., it was shown that teaching students about the evidence for evolution increased their understanding of evolution during a college-level course in biology. For more information on how to teach about evolution, see The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as 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 study living organisms. But evolution isn't just something that happened in the past; it's an ongoing process taking place in the present. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The results are usually easy to see.

However, it wasn't until late-1980s that biologists realized that natural selection could be observed in action as well. The key to this is that different traits result in a different rate of survival and reproduction, and they can be passed on from one generation to another.

In the past, when one particular allele - the genetic sequence that controls coloration - was present in a population of interbreeding organisms, it might rapidly become more common than other alleles. In time, this could mean that 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.

Observing evolutionary change in action is easier when a particular species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples from each population were taken regularly, and more than 50,000 generations of E.coli have passed.

Lenski's work has shown that mutations can alter the rate at which change occurs and the rate at which a population reproduces. It also shows that evolution takes time, which is hard for some to accept.

Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in populations that have used insecticides. That's because the use of pesticides creates a pressure that favors individuals who have resistant genotypes.

The rapid pace at which evolution can take place has led to an increasing appreciation of its importance in a world that is shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding evolution will assist you in making better choices regarding the future of the planet and its inhabitants.

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