The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those interested in the sciences comprehend the evolution theory and how it can be applied across all areas of scientific research.
This site provides a range of resources for students, teachers, and general readers on evolution. It contains key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of life. It is a symbol of love and unity in many cultures. It also has practical applications, such as providing a framework to understand the evolution of species and how they respond to changes in environmental conditions.
Early approaches to depicting the world of biology focused on the classification of organisms into distinct categories that were distinguished by their physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms, or sequences of small DNA fragments, significantly expanded the diversity that could be included in a tree of life2. These trees are mostly populated by eukaryotes, and the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular techniques allow us to construct trees using sequenced markers, such as the small subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of diversity to be discovered. This is especially the case for microorganisms which are difficult to cultivate, and are typically present in a single sample5. A recent analysis of all genomes produced an initial draft of a Tree of Life. This includes a large number of bacteria, archaea and other organisms that have not yet been isolated, or their diversity is not fully understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats require special protection. This information can be used in a variety of ways, such as finding new drugs, battling diseases and improving crops. This information is also useful to conservation efforts. It can help biologists identify 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 funding to protect biodiversity are essential, the best method to preserve the world's biodiversity is to equip the people of developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) illustrates the relationship between different organisms. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree that illustrates the evolutionary relationships between taxonomic categories. The role of phylogeny is crucial in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits are either analogous or homologous. 에볼루션 블랙잭 are the same in their evolutionary paths. Analogous traits could appear like they are however they do not have the same ancestry. Scientists group similar traits into a grouping called a the clade. All members of a clade share a characteristic, for example, amniotic egg production. They all derived from an ancestor who had these eggs. A phylogenetic tree is constructed by connecting clades to identify the species which are the closest to one another.
For a more precise and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the connections between organisms. This information is more precise and provides evidence of the evolutionary history of an organism. Molecular data allows researchers to identify the number of species that have an ancestor common to them and estimate their evolutionary age.
Phylogenetic relationships can be affected by a variety of factors, including the phenomenon of phenotypicplasticity. This is a type of behavior that alters due to unique environmental conditions. This can cause a characteristic to appear more similar to a species than to the other and obscure the phylogenetic signals. This problem can be mitigated by using cladistics, which incorporates an amalgamation of homologous and analogous features in the tree.
In addition, phylogenetics helps determine the duration and rate at which speciation takes place. This information can aid conservation biologists in making choices about which species to safeguard from disappearance. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have come up with theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could evolve according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy and Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of traits can cause changes that are passed on to the
In the 1930s and 1940s, theories from various fields, including genetics, natural selection and particulate inheritance -- came together to form the current evolutionary theory synthesis which explains how evolution happens through the variation of genes within a population and how those variations change in time as a result of natural selection. This model, which encompasses mutations, genetic drift in gene flow, and sexual selection, can be mathematically described mathematically.
Recent discoveries in evolutionary developmental biology have revealed the ways in which variation can be introduced to a species via genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution, which is defined by change in the genome of the species over time, and also by changes in phenotype as time passes (the expression of that genotype in the individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all areas of biology. In a study by Grunspan and co., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. To learn more about how to teach about evolution, please look up 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 studied evolution through looking back in the past--analyzing fossils and comparing species. They also study living organisms. Evolution is not a distant moment; it is an ongoing process. Bacteria mutate and resist antibiotics, viruses evolve and escape new drugs and animals change their behavior to a changing planet. The changes that result are often visible.
It wasn't until late 1980s that biologists realized that natural selection could be seen in action, as well. The key to this is that different traits can confer an individual rate of survival and reproduction, and they can be passed on from one generation to another.
In the past, if one particular allele--the genetic sequence that controls coloration - was present in a population of interbreeding species, it could quickly become more prevalent than all other alleles. As time passes, that could mean 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 the biologist Richard Lenski has been tracking twelve populations of E. 에볼루션 블랙잭 that descended from a single strain; samples of each population are taken every day and more than 50,000 generations have now 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 are unable to accept.
Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more prevalent in areas that have used insecticides. Pesticides create an exclusive pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a growing recognition of its importance particularly in a world which is largely shaped by human activities. This includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding the evolution process will aid you in making better decisions about the future of the planet and its inhabitants.