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The Academy's Evolution Site

Biology is one of the most central concepts in biology. The Academies have long been involved in helping people who are interested in science understand the theory of evolution and how it influences all areas of scientific research.

This site provides teachers, students and general readers with a variety of educational resources on evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.

Tree of Life

The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is seen in a variety of religions and cultures as symbolizing unity and love. It also has practical applications, such as providing a framework for understanding the history of species and how they react to changes in environmental conditions.

The first attempts at depicting the world of biology focused on categorizing organisms into distinct categories which had been identified by their physical and metabolic characteristics1. These methods rely on the sampling of different 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 bacteria are largely underrepresented3,4.

In avoiding the necessity of direct observation and experimentation genetic techniques have made it possible to depict the Tree of Life in a more precise manner. We can construct trees by using molecular methods, such as the small-subunit ribosomal gene.

Despite the dramatic growth of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is especially true of microorganisms, which can be difficult to cultivate and are typically only found in a single sample5. A recent study of all known genomes has produced a rough draft of the Tree of Life, including many bacteria and archaea that are not isolated and whose diversity is poorly understood6.

This expanded Tree of Life can be used to assess the biodiversity of a particular area and determine if certain habitats require special protection. The information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing crop yields. It is also beneficial for conservation efforts. It can aid biologists in identifying areas that are likely to be home to cryptic species, which may have vital metabolic functions, and could be susceptible to human-induced change. While funding to protect biodiversity are important, the best method to protect the biodiversity of the world is to equip the people of developing nations with the information they require to act locally and support conservation.

Phylogeny

A phylogeny (also known as an evolutionary tree) illustrates the relationship between species. Utilizing molecular data as well as morphological similarities and distinctions or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolution of taxonomic groups. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.

A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and evolved from an ancestor with common traits. These shared traits may 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 group similar traits together into a grouping known as a clade. All members of a clade share a characteristic, like amniotic egg production. They all evolved from an ancestor that had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the species that are most closely related to one another.

For a more detailed and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to establish the relationships among organisms. This data is more precise than the morphological data and provides evidence of the evolutionary history of an individual or group. The use of molecular data lets researchers identify the number of organisms who share the same ancestor and estimate their evolutionary age.

Phylogenetic relationships can be affected by a number of factors such as the phenomenon of phenotypicplasticity. This is a type behaviour that can change as a result of unique environmental conditions. This can cause a trait to appear more resembling to one species than to the other which can obscure the phylogenetic signal. However, this problem can be reduced by the use of methods such as cladistics which combine homologous and analogous features into the tree.

Additionally, phylogenetics can help determine the duration and speed at which speciation occurs. This information can aid conservation biologists in making decisions about which species to protect from extinction. In the end, it's the preservation of phylogenetic diversity that will result in an ecologically balanced and complete ecosystem.

Evolutionary Theory

The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Several theories of evolutionary change have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, 바카라 에볼루션 as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that could be passed on to the offspring.

In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection and particulate inheritance -- came together to form the modern evolutionary theory synthesis, which defines how evolution occurs through the variations of genes within a population, and how those variants change in time due to natural selection. This model, known as genetic drift or mutation, gene flow, and sexual selection, is a key element of modern evolutionary biology and is mathematically described.

Recent developments in the field of evolutionary developmental biology have revealed that variations can be introduced into a species via mutation, genetic drift and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, along with others, such as the directional selection process and the 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 the phenotype (the expression of genotypes in an individual).

Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all aspects of biology. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution increased students' understanding of evolution in a college-level biology course. For more details about how to teach evolution read The Evolutionary Potential 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 studying fossils, comparing species and studying living organisms. Evolution is not a past moment; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses re-invent themselves and escape new drugs and animals change their behavior 에볼루션 블랙잭 to the changing climate. The resulting changes are often easy to see.

It wasn't until the 1980s when biologists began to realize that natural selection was at work. The key is that different characteristics result in different rates of survival and reproduction (differential fitness) and can be transferred from one generation to the next.

In the past, if a certain allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could be more common than other allele. In time, this could mean that the number of moths that have 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.

It is easier to observe evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. Samples from each population have been collected frequently and more than 500.000 generations of E.coli have been observed to have passed.

Lenski's work has demonstrated that a mutation can dramatically alter the rate at the rate at which a population reproduces, 에볼루션 카지노 and consequently the rate at which it changes. It also demonstrates that evolution takes time, something that is hard for some to accept.

Another example of microevolution is how mosquito genes that confer resistance to pesticides appear more frequently in areas where insecticides are employed. This is because pesticides cause an enticement that favors individuals who have resistant genotypes.

The rapid pace at which evolution takes place has led to an increasing appreciation of its importance in a world that is shaped by human activity--including climate changes, 에볼루션 pollution and the loss of habitats which prevent the species from adapting. Understanding evolution can help us make smarter decisions regarding the future of our planet, and 에볼루션 사이트 the life of its inhabitants.