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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 incorporated across all areas of scientific research.

This site provides students, teachers and general readers with a wide range of learning resources on evolution. It has the most important video clips from NOVA and the WGBH-produced science programs on DVD.

Tree of Life

The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is an emblem of love and unity across many cultures. It has many practical applications in addition to providing a framework for understanding the history of species, and 에볼루션 (Www.meetme.com) how they respond to changing environmental conditions.

Early attempts to describe the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods, based on the sampling of various parts of living organisms, or short DNA fragments, significantly expanded the diversity that could be included in the tree of life2. These trees are mostly populated by eukaryotes, and bacteria are largely underrepresented3,4.

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

Despite the massive expansion of the Tree of Life through genome sequencing, a lot of biodiversity remains to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are often only represented in a single specimen5. Recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that haven't yet been identified or their diversity is not thoroughly understood6.

The expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if certain habitats need special protection. This information can be used in a variety of ways, from identifying the most effective treatments to fight disease to enhancing crop yields. The information is also beneficial for conservation efforts. It can aid biologists in identifying areas most likely to have cryptic species, which may have vital metabolic functions and are susceptible to changes caused by humans. While funds to protect biodiversity are important, the most effective method to protect the world's biodiversity is to empower more people in developing nations with the necessary knowledge to act locally and promote conservation.

Phylogeny

A phylogeny, also known as an evolutionary tree, illustrates the relationships between different groups of organisms. By using molecular information, 에볼루션 룰렛 morphological similarities and differences, or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree that illustrates the evolution of taxonomic groups. The concept of phylogeny is fundamental to understanding evolution, biodiversity and 에볼루션 슬롯게임 genetics.

A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestors. These shared traits could be either homologous or analogous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look similar, but do not share the same origins. Scientists combine similar traits into a grouping referred to as a the clade. All organisms in a group share a characteristic, like amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree is constructed by connecting the clades to determine the organisms that are most closely related to one another.

For a more detailed and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. Researchers can use Molecular Data to calculate the age of evolution of organisms and identify the number of organisms that share an ancestor common to all.

The phylogenetic relationships of a species can be affected by a number of factors that include the phenotypic plasticity. This is a type behaviour that can change as a result of unique environmental conditions. This can cause a characteristic to appear more similar to one species than another, clouding the phylogenetic signal. This problem can be mitigated by using cladistics, which incorporates the combination of homologous and analogous traits in the tree.

In addition, phylogenetics helps determine the duration and rate of speciation. This information can aid conservation biologists to make decisions about which species they should protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.

Evolutionary Theory

The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Several theories of evolutionary change 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, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed onto offspring.

In the 1930s and 1940s, ideas from various fields, including genetics, natural selection and particulate inheritance - came together to form the current synthesis of evolutionary theory that explains how evolution happens through the variation of genes within a population, and how those variations change in time as a result of natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically explained.

Recent developments in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species via mutation, genetic drift and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, along with other ones 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 the change in phenotype as time passes (the expression of that genotype in an individual).

Students can better understand 에볼루션 슬롯게임 phylogeny by incorporating evolutionary thinking into all aspects of biology. A recent study by Grunspan and colleagues, for instance, showed that teaching about the evidence supporting evolution increased students' acceptance 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 in Life Sciences Education.

Evolution in Action

Scientists have studied evolution through looking back in the past--analyzing 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 right now. Viruses evolve to stay away from new antibiotics and 에볼루션 바카라 체험 bacteria transform to resist antibiotics. Animals alter their behavior in the wake of a changing environment. The results are usually visible.

It wasn't until the 1980s that biologists began realize that natural selection was also in play. The key is that various 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 one allele - the genetic sequence that determines colour - was found in a group of organisms that interbred, it could be more common than other allele. As time passes, this could mean that the number of moths sporting black pigmentation in a group could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

Monitoring evolutionary changes in action is much easier when a species has a rapid turnover of its generation 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 over fifty thousand generations have been observed.

Lenski's research has shown that a mutation can dramatically alter the efficiency with which a population reproduces--and so the rate at which it alters. It also shows evolution takes time, which is hard for some to accept.

Another example of microevolution is how mosquito genes that are resistant to pesticides appear more frequently in populations in which insecticides are utilized. This is because the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.

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