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The Academy's Evolution Site

Biology is a key concept in biology. The Academies are committed to helping those interested in science understand evolution theory and how it is permeated across all areas of scientific research.

This site provides a range of tools 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 of the interconnectedness of life. It is an emblem of love and unity across many cultures. It also has many practical applications, like providing a framework to understand the history of species and how they react to changes in environmental conditions.

Early attempts to represent the biological world were built on categorizing organisms based on their metabolic and physical characteristics. 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. These trees are mostly populated by eukaryotes and bacterial diversity is vastly underrepresented3,4.

By avoiding the need for 에볼루션 무료체험; www.daoban.org, direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a more precise manner. Particularly, molecular techniques enable us to create trees using sequenced markers, such as the small subunit ribosomal RNA gene.

Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. 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 known to date has produced a rough draft of the Tree of Life, including numerous bacteria and archaea that are not isolated and their diversity is not fully understood6.

This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine if specific habitats require protection. The information can be used in a variety of ways, from identifying the most effective remedies to fight diseases to improving crops. This information is also extremely valuable for conservation efforts. It can help biologists identify areas most likely to have species that are cryptic, 에볼루션 무료 바카라 which could perform important metabolic functions and 에볼루션 바카라 무료 are susceptible to changes caused by humans. While funding to protect biodiversity are essential, the best method to protect the world's biodiversity is to empower more people in developing countries with the information they require to act locally and support conservation.

Phylogeny

A phylogeny, also known as an evolutionary tree, reveals the relationships between various groups of organisms. Using molecular data, morphological similarities and differences, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolution of taxonomic groups. Phylogeny is crucial in understanding evolution, biodiversity and genetics.

A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms with similar characteristics and have evolved from an ancestor that shared traits. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary journey. Analogous traits might appear similar however they do not share the same origins. Scientists put similar traits into a grouping referred to as a the clade. For instance, all of the species in a clade share the trait of having amniotic eggs and evolved from a common ancestor who had eggs. The clades are then linked to form a phylogenetic branch to identify organisms that have the closest relationship to.

For a more precise and accurate phylogenetic tree, scientists rely on molecular information from DNA or RNA to establish the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. The use of molecular data lets researchers identify the number of organisms that have the same ancestor and estimate their evolutionary age.

The phylogenetic relationship can be affected by a variety of factors such as the phenotypic plasticity. This is a kind of behaviour that can change due to specific environmental conditions. This can cause a trait to appear more similar to a species than another and obscure the phylogenetic signals. However, this problem can be cured by the use of methods like cladistics, which incorporate a combination of analogous and homologous features into the tree.

In addition, phylogenetics can help predict the length and speed of speciation. This information can aid conservation biologists to make decisions about which species to protect from extinction. In the end, it's the preservation of phylogenetic diversity which will lead to an ecologically balanced and complete ecosystem.

Evolutionary Theory

The central theme of evolution is that organisms acquire different features over time based on their interactions with their environments. Many theories of evolution have been developed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits can cause changes that could be passed on to the offspring.

In the 1930s and 1940s, ideas from different areas, including natural selection, genetics & particulate inheritance, came 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 change with time due to natural selection. This model, known as genetic drift, mutation, gene flow and sexual selection, 에볼루션 바카라 무료 is a key element of current evolutionary biology, and is mathematically described.

Recent developments in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species through mutation, genetic drift and reshuffling genes during sexual reproduction, as well as through the movement of populations. These processes, in conjunction with others such as the directional selection process and the erosion of genes (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes in individuals).

Students can better understand phylogeny by incorporating evolutionary thinking in all areas of biology. In a study by Grunspan and co., it was shown that teaching students about the evidence for 에볼루션 바카라사이트 evolution boosted their understanding of evolution in a college-level course in biology. For more details on how to teach evolution, see The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily: a Framework for Integrating Evolution into Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species, and observing living organisms. But evolution isn't just something that happened in the past, it's an ongoing process, happening today. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of a changing environment. The changes that result are often visible.

It wasn't until late-1980s that biologists realized that natural selection can be seen in action, as well. The reason is that different traits have different rates of survival and reproduction (differential fitness) and can be passed down from one generation to the next.

In the past, if an allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it might become more prevalent than any other allele. In time, this could mean that the number of moths with 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 track evolution when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking 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 passed.

Lenski's research has revealed that mutations can drastically alter the speed at which a population reproduces--and so, the rate at which it evolves. It also proves that evolution takes time--a fact that some are unable to accept.

Another example of microevolution is the way mosquito genes that confer resistance to pesticides appear more frequently in populations in which insecticides are utilized. This is due to pesticides causing a selective pressure which favors individuals who have resistant genotypes.

The rapid pace of evolution taking place has led to an increasing recognition of its importance in a world shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adjusting. Understanding the evolution process can help us make better choices about the future of our planet as well as the life of its inhabitants.