The Academy's Evolution Site
Biology is one of the most important concepts in biology. The Academies have long been involved in helping people who are interested in science comprehend the theory of evolution and how it influences all areas of scientific exploration.
This site provides a wide range of sources for students, teachers 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 an emblem of love and unity across many cultures. It also has practical applications, like providing a framework for understanding the evolution of species and how they react to changing environmental conditions.
The first attempts at depicting the biological world focused on the classification of organisms into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, which relied on sampling of different parts of living organisms, or small DNA fragments, greatly increased the variety of organisms that could be represented in the tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a much more accurate way. We can create trees using molecular techniques, such as the small-subunit ribosomal gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially the case for microorganisms which are difficult to cultivate, and which are usually only found in a single specimen5. A recent analysis of all genomes resulted in an unfinished draft of the Tree of Life. This includes a large number of bacteria, archaea and other organisms that haven't yet been isolated or the diversity of which is not well understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats need special protection. This information can be used in many ways, including finding new drugs, fighting diseases and enhancing crops. It is also beneficial to conservation efforts. It can help biologists identify areas that are likely to be home to cryptic species, which may have vital metabolic functions, and could be susceptible to changes caused by humans. Although funding to protect biodiversity are crucial, ultimately the best way to protect the world's biodiversity is for more people in developing countries to be equipped with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationship of taxonomic groups using molecular data and morphological similarities or differences. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from an ancestor that shared traits. These shared traits can be homologous, or analogous. Homologous traits are identical in their evolutionary roots while analogous traits appear similar but do not have the identical origins. Scientists combine similar traits into a grouping known as a the clade. For instance, all of the organisms that make up a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor that had eggs. A phylogenetic tree is built by connecting the clades to identify the organisms that are most closely related to one another.
Scientists use molecular DNA or RNA data to build a phylogenetic chart that is more precise and precise. This information is more precise than morphological information and gives evidence of the evolutionary history of an organism or group. Molecular data allows researchers to determine the number of organisms who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a variety of factors such as the phenomenon of phenotypicplasticity. This is a kind of behaviour that can change due to particular environmental conditions. This can cause a characteristic to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this issue can be cured by the use of techniques like cladistics, which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics can help predict the duration and rate of speciation. This information can aid conservation biologists in making choices about which species to save from disappearance. In the end, it's the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The main idea behind evolution is that organisms change over time due to their interactions with their environment. Many theories of evolution have been developed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its needs, 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 non-use of traits causes changes that could be passed on to the offspring.
In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection and particulate inheritance - came together to create the modern synthesis of evolutionary theory that explains how evolution happens through the variations of genes within a population and how those variations change in time as a result of natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is the foundation of current evolutionary biology, and can be mathematically explained.
Recent developments in the field of 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 like directional selection and genetic erosion (changes in the frequency of the genotype over time), can lead to 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 phylogeny by incorporating evolutionary thinking throughout all aspects of biology. In a study by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution during the course of a college biology. To find out more about how to teach about evolution, read The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past, analyzing fossils and comparing species. They also study living organisms. Evolution is not a past event; it is a process that continues today. Bacteria mutate and resist antibiotics, viruses evolve and escape new drugs and animals change their behavior in response to a changing planet. The resulting changes are often evident.
But it wasn't until the late 1980s that biologists realized that natural selection could be seen in action, as well. The key is the fact that different traits result in a different rate of survival and reproduction, and can be passed on from one generation to another.
In the past, if a certain allele - the genetic sequence that determines colour was present in a population of organisms that interbred, it could be more common than any other allele. Over time, that would mean the number of black moths in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
The ability to observe evolutionary change is much easier when a species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. 에볼루션코리아 of each population have been taken frequently and more than 50,000 generations of E.coli have been observed to have passed.
just click the following document has shown that mutations can drastically alter the rate at which a population reproduces and, consequently the rate at which it evolves. It also demonstrates that evolution takes time, which is difficult for some to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides show up more often in populations where insecticides are used. This is due to pesticides causing an exclusive pressure that favors those who have resistant genotypes.
The rapid pace at which evolution takes place has led to a growing appreciation of its importance in a world that is shaped by human activity--including climate change, pollution and the loss of habitats which prevent the species from adapting. Understanding evolution can help us make better choices about the future of our planet, and the life of its inhabitants.