The Academy's Evolution Site
Biology is a key concept in biology. The Academies have been for a long time involved in helping people who are interested in science comprehend the concept of evolution and how it affects every area of scientific inquiry.
This site offers a variety of tools 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 is an ancient symbol that represents the interconnectedness of all life. It is a symbol of love and unity across many cultures. It also has practical uses, like providing a framework to understand the history of species and how they react to changes in environmental conditions.
Early attempts to describe the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on the sampling of different parts of living organisms or small DNA fragments, significantly expanded the diversity that could be included in a tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
By avoiding 에볼루션 for direct experimentation and observation genetic techniques have made it possible to depict the Tree of Life in a more precise manner. Trees can be constructed using molecular methods like the small-subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are usually only present in a single specimen5. A recent analysis of all genomes produced an initial draft of the Tree of Life. This includes a wide range of archaea, bacteria and other organisms that have not yet been isolated, or the diversity of which is not well understood6.
The expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if certain habitats need special protection. The information can be used in a variety of ways, from identifying new medicines to combating disease to improving the quality of crops. This information is also extremely valuable for conservation efforts. It helps biologists determine the areas most likely to contain cryptic species that could have significant metabolic functions that could be vulnerable to anthropogenic change. While funds to protect biodiversity are crucial but the most effective way to protect the world's biodiversity is for more people living 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, reveals the connections between various groups of organisms. Scientists can construct a phylogenetic chart that shows the evolution of taxonomic categories using molecular information and morphological differences or similarities. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and evolved from an ancestor with common traits. These shared traits can be analogous or homologous. Homologous traits are similar in their evolutionary roots and analogous traits appear similar but do not have the same ancestors. Scientists group similar traits together into a grouping known as a clade. All members of a clade have a common characteristic, like amniotic egg production. They all evolved from an ancestor who had these eggs. The clades then join to create a phylogenetic tree to determine the organisms with the closest relationship.
To create a more thorough and precise phylogenetic tree scientists use molecular data from DNA or RNA to determine the relationships between organisms. This information is more precise than morphological information and provides evidence of the evolution background of an organism or group. Researchers can utilize Molecular Data to estimate the evolutionary age of living organisms and discover the number of organisms that have the same ancestor.
Phylogenetic relationships can be affected by a variety of factors, including phenotypicplasticity. This is a type behaviour that can change as a result of specific environmental conditions. This can cause a trait to appear more resembling to one species than another and obscure the phylogenetic signals. However, this issue can be reduced by the use of techniques such as cladistics that include a mix of analogous and homologous features into the tree.
In addition, phylogenetics can aid in predicting the time and pace of speciation. This information can assist conservation biologists decide which species to protect from extinction. In the end, it's the conservation of phylogenetic variety that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme of evolution is that organisms acquire different features over time as a result of their interactions with their surroundings. Many scientists have come up with theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would develop according to its own requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of traits can lead to changes that can be passed on to future generations.
In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance - came together to form the modern evolutionary theory which explains how evolution is triggered by the variations of genes within a population and how those variations change in time due to natural selection. This model, known as genetic drift, mutation, gene flow, and sexual selection, is a key element of current evolutionary biology, and is mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species through mutation, genetic drift and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as other ones like the directional selection process and the erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time as well as changes in the phenotype (the expression of genotypes in individuals).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking throughout all aspects of biology. In a study by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution during an undergraduate biology course. For more details about how to teach evolution look up The Evolutionary Potential 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 studying fossils, comparing species and observing living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior because of the changing environment. The resulting changes are often visible.
However, it wasn't until late 1980s that biologists understood that natural selection can be seen in action, as well. The key is that various characteristics result in different rates of survival and reproduction (differential fitness) and can be passed from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it could be more prevalent than any other allele. As time passes, that could mean that the number of black moths within the 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 easier when a species has a rapid generation turnover like bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples from each population are taken every day and more than 50,000 generations have now been observed.
Lenski's research has demonstrated that mutations can alter the rate of change and the rate of a population's reproduction. It also demonstrates that evolution takes time, which is hard for some to accept.
Another example of microevolution is the way mosquito genes for resistance to pesticides show up more often in populations in which insecticides are utilized. This is because pesticides cause a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to a greater appreciation of its importance especially in a planet that is largely shaped by human activity. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding evolution can help us make smarter decisions regarding the future of our planet, and the lives of its inhabitants.