The Academy's Evolution Site
The concept of biological evolution is among the most fundamental 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 affects all areas of scientific research.
This site provides a range of sources for students, teachers, and general readers on evolution. It has important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of all life. 에볼루션 바카라 is seen in a variety of spiritual traditions and cultures as an emblem of unity and love. It has many practical applications as well, including providing a framework for understanding the history of species, and how they respond to changing environmental conditions.
Early attempts to represent the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, based on the sampling of different parts of living organisms or on short fragments of their DNA significantly increased the variety that could be included in the tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
Genetic techniques have greatly broadened our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees by using molecular methods like the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is a lot of diversity to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are usually only found in a single specimen5. A recent study of all genomes known to date has produced a rough draft version of the Tree of Life, including numerous archaea and bacteria that have not been isolated and whose diversity is poorly understood6.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine whether specific habitats require protection. This information can be utilized in many ways, including identifying new drugs, combating diseases and enhancing crops. This information is also extremely useful for conservation efforts. It can help biologists identify areas most likely to be home to species that are cryptic, which could have vital metabolic functions and be vulnerable to human-induced change. While funds to protect biodiversity are essential, the best way to conserve the world's biodiversity is to empower more people in developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, illustrates the connections between various groups of organisms. Scientists can create a phylogenetic chart that shows the evolutionary relationship of taxonomic groups using molecular data and morphological differences or similarities. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar traits and have evolved from an ancestor that shared traits. These shared traits could be either homologous or analogous. Homologous traits are identical in their evolutionary origins, while analogous traits look similar but do not have the identical origins. Scientists combine similar traits into a grouping known as a Clade. All members of a clade have a common characteristic, like amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree can be built by connecting the clades to identify the organisms that are most closely related to each other.
Scientists use DNA or RNA molecular data to build a phylogenetic chart that is more precise and detailed. This information is more precise and provides evidence of the evolution of an organism. Researchers can use Molecular Data to calculate the evolutionary age of organisms and determine the number of organisms that have the same ancestor.
The phylogenetic relationship can be affected by a variety of factors, including phenotypicplasticity. This is a type behavior that changes due to unique environmental conditions. This can cause a trait to appear more resembling to one species than to another, obscuring the phylogenetic signals. This problem can be addressed by using cladistics, which is a an amalgamation of homologous and analogous features in the tree.
Furthermore, phylogenetics may help predict the length and speed of speciation. This information can aid conservation biologists to make decisions about which species they should protect from extinction. In the end, it's the preservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire different features over time based on their interactions with their environment. Many theories of evolution have been proposed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that could be passed onto 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 that explains how evolution happens through the variation of genes within a population, and how those variants change in time as a result of natural selection. This model, called genetic drift or mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and is mathematically described.
Recent discoveries in evolutionary developmental biology have revealed how variation can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with others, such as the directional selection process and the erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in individuals).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking throughout all aspects of biology. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution increased students' understanding of evolution in a college biology class. To find out more about how to teach about evolution, please see The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back--analyzing fossils, comparing species and studying living organisms. However, evolution isn't something that happened in the past, it's an ongoing process, taking place today. Bacteria transform and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals alter their behavior to a changing planet. The changes that result are often visible.
It wasn't until late 1980s that biologists understood that natural selection can be observed in action as well. The key is that different traits confer different rates of survival and reproduction (differential fitness) and can be passed from one generation to the next.
In the past, if one particular allele, the genetic sequence that defines color in a group of interbreeding species, it could quickly become more common than other alleles. In time, this could mean that the number of black moths in a particular population could rise. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
에볼루션 바카라 to observe evolutionary change is easier when a particular species has a rapid turnover of its generation such as bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. Samples from each population have been taken regularly and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's work has shown that mutations can alter the rate of change and the rate at which a population reproduces. It also shows evolution takes time, something that is difficult for some to accept.
Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more common in populations where insecticides are used. Pesticides create an enticement that favors those with resistant genotypes.
The speed 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 change, pollution, and the loss of habitats that prevent the species from adapting. Understanding evolution can help us make smarter choices about the future of our planet, and the lives of its inhabitants.