The Academy's Evolution Site
Biology is one of the most important concepts in biology. The Academies have been active for a long time in helping those interested in science understand the theory of evolution and how it influences every area of scientific inquiry.
This site provides students, teachers and general readers with a variety of learning resources on evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
에볼루션 바카라 무료 of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It appears in many spiritual traditions and cultures as symbolizing unity and love. It also has many practical applications, like providing a framework to understand the evolution of species and how they respond to changes in the environment.
The earliest attempts to depict the world of biology focused on categorizing organisms into distinct categories that were identified by their physical and metabolic characteristics1. These methods, based on sampling of different parts of living organisms, or short fragments of their DNA significantly increased the variety that could be represented in the tree of life2. These trees are largely composed by eukaryotes and the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. Trees can be constructed using molecular methods, such as the small-subunit ribosomal gene.
Despite the dramatic growth of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is especially relevant to microorganisms that are difficult to cultivate and are usually found in one sample5. Recent analysis of all genomes produced a rough draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated, or the diversity of which is not thoroughly understood6.
This expanded Tree of Life can be used to determine the diversity of a specific region and determine if particular habitats require special protection. This information can be utilized in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely useful for conservation efforts. It can help biologists identify areas that are likely to be home to species that are cryptic, which could perform important metabolic functions and be vulnerable to the effects of human activity. While funds to protect biodiversity are important, the best method to protect the world's biodiversity is to equip the people of developing nations with the necessary knowledge to act locally and support conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between organisms. Using molecular data similarities and differences in morphology or ontogeny (the process of the development of an organism) scientists can create an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits could be either homologous or analogous. Homologous traits are similar in their evolutionary roots, while analogous traits look similar, but do not share the identical origins. Scientists arrange similar traits into a grouping referred to as a Clade. For example, all of the organisms that make up a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor who had these eggs. The clades are then connected to create a phylogenetic tree to determine the organisms with the closest relationship to.
To create a more thorough and precise 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 evolution history of an organism. The analysis of molecular data can help researchers identify the number of species who share the same ancestor and estimate their evolutionary age.
The phylogenetic relationship can be affected by a variety of factors, including the phenotypic plasticity. This is a type of behavior that alters as a result of unique environmental conditions. This can cause a particular trait to appear more like a species another, clouding the phylogenetic signal. This problem can be addressed by using cladistics, which incorporates the combination of analogous and homologous features in the tree.
In addition, phylogenetics helps determine the duration and speed of speciation. This information will assist conservation biologists in making decisions about which species to save from extinction. Ultimately, it is the preservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms develop distinct characteristics over time due to their interactions with their environments. Many theories of evolution have been proposed by a wide range of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that can be passed on to the offspring.
In the 1930s and 1940s, concepts 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 happens through the variations of genes within a population, and how those variations change over time due to natural selection. This model, which encompasses mutations, genetic drift in gene flow, and sexual selection is mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have shown that variations can be introduced into a species through mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of the genotype over time) can result in evolution which is defined by changes in the genome of the species over time, and the change in phenotype as time passes (the expression of that genotype within the individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking in all areas of biology. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution increased students' acceptance of evolution in a college biology course. For more information on how to teach about evolution, look up The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past--analyzing fossils and comparing species. They also observe living organisms. Evolution isn't a flims moment; it is an ongoing process. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior because of a changing environment. The results are often visible.
It wasn't until the 1980s that biologists began realize that natural selection was at work. The key to this is that different traits can confer the ability to survive at different rates and reproduction, and they can be passed down from generation to generation.
In the past, when one particular allele - the genetic sequence that defines color in a group of interbreeding organisms, it might rapidly become more common than other alleles. As time passes, this could mean that the number of moths with black pigmentation in a group may 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 much easier when a species has a fast generation turnover like bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples from each population are taken every day and more than fifty thousand generations have been observed.
Lenski's work has demonstrated that a mutation can dramatically alter the efficiency with which a population reproduces and, consequently, the rate at which it evolves. It also shows that evolution takes time, which is difficult for some to accept.
Another example of microevolution is that mosquito genes that confer resistance to pesticides appear more frequently in areas in which insecticides are utilized. That's because the use of pesticides creates a pressure that favors people with resistant genotypes.
The rapidity of evolution has led to a growing recognition of its importance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution can help us make better decisions about the future of our planet, and the life of its inhabitants.