The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are involved in helping those who are interested in the sciences learn about the theory of evolution and how it is incorporated across all areas of scientific research.
This site provides a wide range of tools for teachers, students and general readers of evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and harmony in a variety of cultures. It has many practical applications as well, including providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
Early approaches to depicting the biological world focused on the classification of organisms into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which relied on sampling of different parts of living organisms, or small fragments of their DNA significantly increased the variety that could be represented in a tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
에볼루션 바카라 무료체험 have greatly broadened our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to build trees using sequenced markers, such as the small subunit of ribosomal RNA gene.
The Tree of Life has been significantly expanded by genome sequencing. However, there is still much diversity to be discovered. This is particularly relevant to microorganisms that are difficult to cultivate and are typically found in a single specimen5. A recent analysis of all genomes produced an unfinished draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that haven't yet been isolated, or whose diversity has not been fully understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if certain habitats require protection. This information can be utilized in a variety of ways, such as finding new drugs, battling diseases and improving crops. This information is also extremely valuable in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with potentially significant metabolic functions that could be at risk of anthropogenic changes. While funds to safeguard biodiversity are vital but the most effective way to preserve the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny is also known as an evolutionary tree, illustrates the connections between groups of organisms. Scientists can build an phylogenetic chart which shows the evolutionary relationship of taxonomic groups based on molecular data and morphological similarities or differences. Phylogeny is crucial in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestors. These shared traits can be analogous, or homologous. Homologous traits share their evolutionary roots while analogous traits appear like they do, but don't have the identical origins. Scientists arrange similar traits into a grouping known as a the clade. For instance, all the organisms in a clade share the trait of having amniotic egg and evolved from a common ancestor who had these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms that are most closely related to one another.
Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more precise and precise. This data is more precise than morphological information and provides evidence of the evolutionary history of an organism or group. The analysis of molecular data can help researchers identify the number of species who share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationship can be affected by a number of factors such as the phenotypic plasticity. This is a type behaviour that can change in response to particular environmental conditions. This can cause a particular trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. This issue can be cured by using cladistics, which is a the combination of analogous and homologous features in the tree.
Additionally, phylogenetics aids determine the duration and speed at which speciation occurs. This information can aid conservation biologists in making choices about which species to protect from disappearance. In the end, it is the conservation of phylogenetic variety which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme of evolution is that organisms develop various characteristics over time as a result of their interactions with their environments. A variety of theories about evolution have been developed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that can be passed on to offspring.
In the 1930s & 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance, were brought together to form a contemporary evolutionary theory. This defines how evolution is triggered by the variations in genes within a population and how these variations change over time as a result of natural selection. This model, which encompasses genetic drift, mutations, gene flow and sexual selection, can be mathematically described mathematically.
Recent discoveries in evolutionary developmental biology have shown the ways in which variation can be introduced to a species through mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of a genotype over time) can lead to evolution which is defined by changes in the genome of the species over time, and also the change in phenotype as time passes (the expression of the genotype in an individual).
Incorporating evolutionary thinking into all aspects of biology education could increase students' understanding of phylogeny and evolutionary. 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-level biology course. To learn more about how to teach about evolution, see The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally looked at evolution through the past--analyzing fossils and comparing species. They also study living organisms. Evolution is not a distant moment; it is a process that continues today. Bacteria mutate and resist antibiotics, viruses re-invent themselves and elude new medications and animals change their behavior in response to the changing environment. The results are usually visible.
But it wasn't until the late 1980s that biologists realized that natural selection can be seen in action, as well. The key is that different characteristics result in different rates of survival and reproduction (differential fitness) and can be passed down from one generation to the next.
In the past, if an allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it might become more prevalent than any other allele. Over time, this would mean that the number of moths with black pigmentation in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is easier when a particular species has a rapid turnover of its generation such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend 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 research has demonstrated that mutations can alter the rate at which change occurs and the efficiency at which a population reproduces. It also demonstrates that evolution takes time, which is difficult for some to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides are more prevalent in populations where insecticides are used. That's because the use of pesticides creates a selective pressure that favors individuals with resistant genotypes.
The rapid pace of evolution taking place has led to a growing recognition of its importance in a world that is shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process can help us make smarter decisions regarding the future of our planet and the life of its inhabitants.