에볼루션 바카라사이트 is a key concept in biology. The Academies are committed to helping those who are interested in science to comprehend the evolution theory and how it can be applied across all areas of scientific research.
This site provides a wide range of resources for teachers, students and general readers of evolution. It includes key video clip 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 important practical applications, like providing a framework for understanding the history of species and how they respond to changes in environmental conditions.
The first attempts at depicting the world of biology focused on categorizing organisms into distinct categories that were distinguished by their physical and metabolic characteristics1. These methods, which rely on the sampling of various parts of living organisms or short DNA fragments, greatly increased the variety of organisms that could be represented in the tree of life2. However these trees are mainly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have enabled us to represent 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 of ribosomal RNA gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly true for microorganisms that are difficult to cultivate, and which are usually only found in one sample5. A recent study of all genomes known to date has created a rough draft of the Tree of Life, including a large number of archaea and bacteria that are not isolated and their diversity is not fully understood6.
This expanded Tree of Life can be used to determine the diversity of a specific area and determine if specific habitats need special protection. The information can be used in a variety of ways, from identifying new remedies to fight diseases to enhancing crops. This information is also extremely useful in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with important metabolic functions that may be at risk of anthropogenic changes. Although funds to safeguard biodiversity are vital, ultimately the best way to protect the world's biodiversity is for more people living in developing countries to be empowered with the knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between various groups of organisms. By using molecular information, 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 categories. Phylogeny is crucial in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits could be either analogous or homologous. Homologous traits are similar in terms of their evolutionary path. Analogous traits may look like they are, but they do not have the same ancestry. Scientists group similar traits into a grouping known as a clade. For example, all of the species in a clade share the characteristic of having amniotic egg and evolved from a common ancestor which had these eggs. A phylogenetic tree can be constructed by connecting the clades to identify the organisms that are most closely related to each other.
For a more precise and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships between organisms. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can use Molecular Data to estimate the age of evolution of living organisms and discover the number of organisms that share a common ancestor.
The phylogenetic relationships between organisms can be influenced by several factors including phenotypic plasticity, a type of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to one species than to another which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics that incorporate a combination of analogous and homologous features into the tree.
Additionally, phylogenetics can aid in predicting the duration and rate of speciation. This information will assist conservation biologists in deciding which species to protect from disappearance. It is ultimately the preservation of phylogenetic diversity that will create an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide range of scientists such as 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 misuse of traits causes changes that can be passed on to the 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 evolutionary theory that explains how evolution is triggered by the variations of genes within a population and how those variants change in time as a result of natural selection. This model, which encompasses genetic drift, mutations in gene flow, and sexual selection is mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have shown how variation can be introduced to a species via genetic drift, mutations, reshuffling genes during sexual reproduction and the movement between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time), can lead to evolution that is defined as changes in the genome of the species over time and also by changes in phenotype over time (the expression of that genotype in the individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all areas of biology. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during 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 as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through looking back--analyzing fossils, comparing species, and observing living organisms. However, evolution isn't something that happened in the past, it's an ongoing process that is taking place in the present. Viruses evolve to stay away from new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The changes that result are often visible.
It wasn't until late 1980s that biologists began to realize that natural selection was in play. The reason is that different traits have different rates of survival and reproduction (differential fitness) and are passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour was present in a population of organisms that interbred, it might become more common than other allele. In time, this could mean that the number of moths that have black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
에볼루션게이밍 is easier to see evolution when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. Samples of each population were taken regularly and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that a mutation can profoundly alter the efficiency with which a population reproduces--and so, the rate at which it evolves. It also shows that evolution takes time--a fact that some people find difficult to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more common in populations that have used insecticides. This is because the use of pesticides creates a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to an increasing recognition of its importance particularly in a world shaped largely by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding the evolution process will aid you in making better decisions about the future of our planet and its inhabitants.