The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies have been active for a long time in helping people who are interested in science understand the concept of evolution and how it influences all areas of scientific research.
This site provides students, teachers and general readers with a range of learning resources on 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 of the interconnectedness of life. It is an emblem of love and unity across many cultures. It has many practical applications as well, including providing a framework for understanding the evolution of species and how they react to changes in environmental conditions.
The first attempts to depict the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on the sampling of different parts of living organisms or on small fragments of their DNA significantly expanded the diversity that could be represented in a tree of life2. These trees are mostly populated by eukaryotes, and bacteria are largely underrepresented3,4.
에볼루션 슬롯 have greatly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed by using molecular methods, such as the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true for microorganisms, which are difficult to cultivate and are typically only present in a single specimen5. 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 haven't yet been identified or their diversity is not well understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, assisting to determine if specific habitats require protection. This information can be used in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. The information is also useful to conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species that could have important metabolic functions that could be at risk of anthropogenic changes. While conservation funds are important, the most effective way to conserve the world's biodiversity is to equip more people in developing nations with the necessary knowledge to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the connections between different groups of organisms. Scientists can build a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny is essential in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestral. These shared traits can be analogous, or homologous. Homologous traits are similar in their evolutionary origins, while analogous traits look similar, but do not share the identical origins. Scientists arrange similar traits into a grouping known as a Clade. All members of a clade have a common trait, such as amniotic egg production. They all evolved from an ancestor that had these eggs. The clades are then connected to form a phylogenetic branch to determine which organisms have the closest relationship to.
Scientists use molecular DNA or RNA data to build a phylogenetic chart which is more precise and detailed. This information is more precise and gives evidence of the evolutionary history of an organism. The analysis of molecular data can help researchers identify the number of organisms who share the same ancestor and estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors such as phenotypicplasticity. This is a kind of behavior that changes as a result of specific environmental conditions. This can cause a characteristic to appear more similar in one species than other species, which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which incorporates the combination of homologous and analogous features in the tree.
In addition, phylogenetics helps predict the duration and rate at which speciation takes place. This information can assist conservation biologists make decisions about which species to protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide range 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 requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to offspring.
In the 1930s and 1940s, ideas from different areas, including genetics, natural selection, and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This defines how evolution happens through the variation of genes in the population and how these variations change over time as a result of natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that variation can be introduced into a species via genetic drift, mutation, and reshuffling of genes in sexual reproduction, and also through the movement of populations. These processes, along with others such as directional selection and gene erosion (changes in the 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 within individuals).
Incorporating evolutionary thinking into all aspects of biology education can increase student understanding of the concepts of phylogeny as well as evolution. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution increased students' understanding of evolution in a college biology course. For more details on how to teach evolution, see The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by studying fossils, comparing species and observing living organisms. But evolution isn't just something that happened in the past, it's an ongoing process, that is taking place right now. Bacteria mutate and resist antibiotics, viruses re-invent themselves and escape new drugs and animals alter their behavior in response to a changing planet. The resulting changes are often easy to see.
But it wasn't until the late-1980s that biologists realized that natural selection could be seen in action, as well. The main reason is that different traits can confer a different rate of survival as well as reproduction, and may be passed down from one generation to another.
In the past when one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding species, it could quickly become more prevalent than the other alleles. Over time, this would mean that the number of moths sporting 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.
It is easier to see evolution when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. Samples of each population have been taken regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that a mutation can profoundly alter the efficiency with which a population reproduces--and so the rate at which it changes. It also shows that evolution is slow-moving, a fact that many find difficult to accept.
Another example of microevolution is the way mosquito genes that confer resistance to pesticides appear more frequently 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 awareness of its significance, especially in a world that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding the evolution process will help us make better decisions regarding the future of our planet, and the life of its inhabitants.