The Academy's Evolution Site
The concept of biological evolution is among the most important concepts in biology. The Academies are committed to helping those who are interested in science to comprehend the evolution theory and how it is incorporated throughout all fields of scientific research.
This site provides students, teachers and general readers with a variety of educational resources on evolution. It has key video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of 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 for understanding the history of species and how they respond to changing environmental conditions.
The first attempts at depicting the biological world focused on the classification of species into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms or sequences of short DNA fragments, significantly increased the variety that could be represented in the tree of life2. However the trees are mostly composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.
By avoiding the need for direct experimentation and observation genetic techniques have enabled us to depict the Tree of Life in a much more accurate way. Particularly, molecular techniques allow us to construct trees by using sequenced markers, such as the small subunit ribosomal RNA 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 particularly true of microorganisms, which are difficult to cultivate and are typically only found in a single specimen5. Recent analysis of all genomes produced an unfinished draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated, or their diversity is not well understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if certain habitats require special protection. The information can be used in a variety of ways, from identifying the most effective remedies to fight diseases to enhancing the quality of the quality of crops. This information is also useful in conservation efforts. It can aid biologists in identifying areas most likely to have cryptic species, which may perform important metabolic functions and are susceptible to human-induced change. While funding to protect biodiversity are important, the most effective method to preserve the world's biodiversity is to empower more people in developing countries with the necessary knowledge to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, illustrates the relationships between groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the course of development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationships between taxonomic groups. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and have evolved from an ancestor with common traits. These shared traits could be homologous, or analogous. Homologous traits are similar in terms of their evolutionary path. Analogous traits might appear similar however they do not have the same origins. Scientists put similar traits into a grouping referred to as a clade. For instance, all of the species in a clade have the characteristic of having amniotic egg and evolved from a common ancestor that had eggs. The clades are then connected to form a phylogenetic branch to determine the organisms with the closest connection to each other.
For a more detailed and accurate phylogenetic tree scientists use molecular data from DNA or RNA to determine the relationships among organisms. This information is more precise than the morphological data and provides evidence of the evolutionary background of an organism or group. Molecular data allows researchers to determine the number of organisms that share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic plasticity a type of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more resembling to one species than another and obscure the phylogenetic signals. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous features in the tree.
Additionally, phylogenetics aids determine the duration and speed of speciation. This information can aid conservation biologists in deciding which species to safeguard from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will create an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms alter over time because of their interactions with their environment. Many theories of evolution have been proposed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to the offspring.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to form a modern evolutionary theory. This describes how evolution occurs by the variation in genes within the population and how these variations change over time as a result of natural selection. This model, called genetic drift or mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and is mathematically described.
Recent advances in evolutionary developmental biology have revealed how variation can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, in conjunction with other ones like the directional selection process and the erosion of genes (changes in frequency of genotypes over time) can lead to evolution. 에볼루션바카라사이트 is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny as well as evolution. In a recent study conducted by Grunspan et al., it was shown that teaching students about the evidence for evolution boosted their acceptance of evolution during an undergraduate biology course. For more details about how to teach evolution, see The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past--analyzing fossils and comparing species. They also observe living organisms. But evolution isn't a thing that occurred in the past, it's an ongoing process happening right now. Bacteria mutate and resist antibiotics, viruses evolve and are able to evade new medications and animals alter their behavior to the changing environment. The results are often visible.
It wasn't until late 1980s that biologists understood that natural selection could be seen in action, as well. The reason is that different characteristics result in different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour was present in a population of organisms that interbred, it could be more common than other allele. Over time, this would mean that the number of moths with black pigmentation in a population 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 evolutionary change when an organism, like bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain. samples of each population are taken regularly, and over 50,000 generations have now passed.
Lenski's work has demonstrated that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently the rate at which it alters. It also demonstrates that evolution takes time, a fact that is hard for some to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides show up more often in areas in which insecticides are utilized. Pesticides create an exclusive pressure that favors individuals who have resistant genotypes.
The rapid pace at which evolution takes place has led to an increasing recognition of its importance in a world shaped by human activity, including climate change, pollution and the loss of habitats that hinder many species from adjusting. Understanding evolution can assist you in making better choices about the future of the planet and its inhabitants.