The Academy's Evolution Site
The concept of biological evolution is among the most central concepts in biology. The Academies are committed to helping those who are interested in science understand evolution theory and how it is incorporated throughout all fields of scientific research.
This site provides teachers, students and general readers with a wide range of learning resources on evolution. It includes key video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It is a symbol of love and unity across many cultures. It also has practical applications, such as providing a framework to understand the history of species and how they react to changes in environmental conditions.
The first attempts to depict the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, based on sampling of different parts of living organisms, or sequences of short fragments of their DNA significantly expanded the diversity that could be represented in the tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded 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.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are often only found in a single sample5. A recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that haven't yet been isolated or the diversity of which is not well understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine whether specific habitats require protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing the quality of crops. This information is also extremely useful in conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species with potentially important metabolic functions that could be at risk from anthropogenic change. Although funding to protect 에볼루션 사이트 are essential, ultimately the best way to ensure the preservation of biodiversity around the world is for more people in developing countries to be equipped with the knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between different groups of organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationship of taxonomic groups based on molecular data and morphological differences or similarities. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that evolved from common ancestors. These shared traits can be either homologous or analogous. Homologous traits are similar in their evolutionary roots, while analogous traits look similar, but do not share the same ancestors. Scientists arrange similar traits into a grouping known as a clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all derived from an ancestor who had these eggs. A phylogenetic tree is then constructed by connecting the clades to identify the organisms which are the closest to each other.
For a more detailed and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to establish the relationships among organisms. This data is more precise than morphological information and provides evidence of the evolution history of an individual or group. The use of molecular data lets researchers identify the number of organisms that have a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between species can be affected by a variety of factors, including phenotypic plasticity a type of behavior that alters in response to specific environmental conditions. This can cause a trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous traits in the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information can aid conservation biologists to decide which species to protect from extinction. In the end, it's the preservation of phylogenetic diversity which will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire different features over time as a result of their interactions with their surroundings. 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 according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that could be passed on to the offspring.
In the 1930s and 1940s, theories from a variety of fields--including natural selection, genetics, and particulate inheritance - came together to form the current evolutionary theory, which defines how evolution happens through the variations of genes within a population, and how those variants change over time due to natural selection. This model, which encompasses mutations, genetic drift in gene flow, and sexual selection can be mathematically described.
에볼루션 룰렛 in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes in sexual reproduction, and also through the movement of populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of a genotype over time) can result in evolution, which is defined by changes in the genome of the species over time, and the change in phenotype over time (the expression of that genotype in the individual).
Incorporating evolutionary thinking into all areas of biology education could increase students' understanding of phylogeny and evolution. In a study by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution in an undergraduate biology course. To learn more about how to teach about evolution, look up The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by studying fossils, comparing species, and observing living organisms. Evolution isn't a flims event; it is a process that continues today. Bacteria evolve and resist antibiotics, viruses evolve and escape new drugs, and animals adapt their behavior in response to the changing environment. The changes that result are often visible.
However, it wasn't until late-1980s that biologists realized that natural selection could be seen in action, as well. The main reason is that different traits result in a different rate of survival and reproduction, and they can be passed on from one generation to another.
In the past, if one allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it could be more common than any other allele. In time, this could 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.
It is easier to see evolution when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. The samples of each population were taken regularly, and more than 50,000 generations of E.coli have passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. 에볼루션 슬롯 shows that evolution takes time, something that 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 employed. This is due to the fact that the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance especially in a planet shaped largely by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution will help you make better decisions about the future of the planet and its inhabitants.