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The Academy's Evolution Site

The concept of biological evolution is among the most fundamental concepts in biology. The Academies have been for a long time involved in helping people who are interested in science understand the concept of evolution and how it influences all areas of scientific research.

This site provides a range of sources for teachers, students, and general readers on evolution. It includes the most important video clips from NOVA and WGBH-produced 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 harmony in a variety of cultures. It can be used in many practical ways as well, including providing a framework for understanding the history of species and how they react to changing environmental conditions.

Early approaches to depicting the biological world focused on categorizing organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods, which rely on the sampling of different parts of living organisms or on sequences of small fragments of their DNA, 에볼루션 바카라사이트 에볼루션 블랙잭 (read on) significantly increased the variety that could be represented in a tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.

Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to construct trees using sequenced markers like the small subunit ribosomal RNA gene.

Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is especially true of microorganisms, which are difficult to cultivate and are typically only present in a single specimen5. Recent analysis of all genomes resulted in an initial draft of the Tree of Life. This includes a wide range of archaea, bacteria, and other organisms that have not yet been isolated, 바카라 에볼루션 or the diversity of which is not fully understood6.

This expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if certain habitats require protection. This information can be utilized in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. This information is also extremely valuable in conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with potentially important metabolic functions that could be at risk from anthropogenic change. 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 to promote conservation from within.

Phylogeny

A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. Utilizing molecular data, morphological similarities and differences, or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree which illustrates the evolution of taxonomic groups. The role of phylogeny is crucial in understanding the relationship between 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 ancestors. These shared traits may be analogous or homologous. Homologous traits are the same in terms of their evolutionary path. Analogous traits might appear like they are but they don't share the same origins. Scientists combine similar traits into a grouping called a clade. Every organism in a group share a characteristic, for 에볼루션 바카라 무료체험 example, amniotic egg production. They all derived from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the organisms which are the closest to each other.

Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more precise and detailed. This data is more precise than morphological data and provides evidence of the evolution history of an organism or group. Researchers can use Molecular Data to estimate the age of evolution of living organisms and 에볼루션 블랙잭 discover how many organisms share an ancestor common to all.

The phylogenetic relationships between organisms can be affected by a variety of factors, including phenotypic flexibility, an aspect of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to a species than another and obscure the phylogenetic signals. However, this problem can be solved through the use of methods such as cladistics which include a mix of analogous and homologous features into the tree.

Additionally, phylogenetics aids determine the duration and speed at which speciation occurs. This information can assist conservation biologists decide which species to protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.

Evolutionary Theory

The main idea behind evolution is that organisms change over time due to their interactions with their environment. Many theories of evolution have been developed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that could be passed on to offspring.

In the 1930s & 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, merged to create a modern evolutionary theory. This defines how evolution is triggered by the variation of genes in the population, and how these variations alter over time due to natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection, can be mathematically described.

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

Incorporating evolutionary thinking into all areas of biology education could increase students' understanding of phylogeny and evolution. In a study by Grunspan and co., it was shown that teaching students about the evidence for evolution increased their understanding of evolution during an undergraduate biology course. To find out more about how to teach about evolution, read The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Traditionally scientists have studied evolution by looking back, studying fossils, comparing species and studying living organisms. Evolution is not a distant moment; it is an ongoing process that continues to be observed today. Bacteria transform and resist antibiotics, viruses evolve and escape new drugs and animals change their behavior in response to a changing planet. The results are usually easy to see.

It wasn't until the 1980s that biologists began realize that natural selection was in play. The key is that various traits confer different rates of survival and reproduction (differential fitness), and can be passed 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, 에볼루션 블랙잭 it could rapidly become more common than other alleles. Over time, this would mean that the number of moths sporting black pigmentation 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 species has a rapid generation turnover like bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples of each are taken regularly and more than 500.000 generations have been observed.

Lenski's work has demonstrated that a mutation can profoundly alter the speed at which a population reproduces--and so the rate at which it changes. It also demonstrates that evolution is slow-moving, a fact that many find hard to accept.

Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more common in populations that have used insecticides. This is due to pesticides causing a selective pressure which favors individuals who have resistant genotypes.

The speed 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 에볼루션 코리아 the loss of habitats that prevent many species from adapting. Understanding evolution will help us make better decisions regarding the future of our planet as well as the lives of its inhabitants.