The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science to learn about the theory of evolution and how it is permeated throughout all fields of scientific research.
This site provides a range of tools for teachers, students as well as general readers about evolution. It includes key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is used in many spiritual traditions and cultures as a symbol of unity and love. It also has many practical applications, such as providing a framework for understanding the evolution of species and how they react to changes in environmental conditions.
Early approaches to depicting the biological world focused on separating species into distinct categories that were distinguished by their physical and metabolic characteristics1. These methods, based on sampling of different parts of living organisms or short fragments of their DNA, greatly increased the variety of organisms that could be included in the tree of life2. However these trees are mainly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding the need for direct observation and experimentation, genetic techniques have enabled us to represent the Tree of Life in a much more accurate way. We can construct trees using molecular techniques, such as the small-subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are often only found in a single sample5. Recent analysis of all genomes has produced a rough draft of a Tree of Life. This includes a large number of bacteria, archaea and other organisms that haven't yet been identified or the diversity of which is not fully understood6.
The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine whether specific habitats require protection. This information can be utilized in many ways, including finding new drugs, fighting diseases and improving the quality of crops. This information is also beneficial to conservation efforts. It can help biologists identify areas that are likely to have cryptic species, which may perform important metabolic functions and be vulnerable to the effects of human activity. 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 information they require to act locally and support conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationships between taxonomic categories using molecular information and morphological differences or similarities. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits could be either analogous or homologous. Homologous traits are the same in terms of their evolutionary journey. Analogous traits could appear like they are however they do not share the same origins. Scientists group similar traits into a grouping known as a the clade. For instance, all the organisms in a clade have the characteristic of having amniotic egg and evolved from a common ancestor who had these eggs. The clades are then connected to form a phylogenetic branch to determine which organisms have the closest relationship.
Scientists make use of molecular DNA or RNA data to create a phylogenetic chart which is more precise and precise. This information is more precise and gives evidence of the evolution of an organism. Molecular data allows researchers to determine the number of organisms that have a common ancestor and to 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 particular environmental conditions. This can cause a characteristic to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this problem can be cured by the use of methods like cladistics, which incorporate a combination of homologous and analogous features into the tree.
In addition, phylogenetics helps determine the duration and speed at which speciation occurs. This information can assist conservation biologists make decisions about which species they should protect from extinction. In the end, it's the conservation of phylogenetic variety that will result in an ecosystem that is complete and balanced.
무료 에볼루션 in evolution is that organisms change over time due to 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 proposed that a living organism develop slowly in accordance with its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that could be passed on to the offspring.
In the 1930s and 1940s, theories from a variety of fields -- including genetics, natural selection and particulate inheritance - came together to create the modern synthesis of evolutionary theory, which defines how evolution occurs through the variation of genes within a population and how those variants change in time due to natural selection. This model, which includes mutations, genetic drift as well as gene flow and sexual selection, can be mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species via genetic drift, mutation, and reshuffling of genes during sexual reproduction, as well as through migration between populations. These processes, as well as others such as directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes within individuals).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking in all areas of biology. In a recent study conducted by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in an undergraduate biology course. To find out more about how to teach about evolution, please read 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 traditionally studied evolution through looking back in the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a past event, but an ongoing process. Bacteria transform and resist antibiotics, viruses re-invent themselves and escape new drugs and animals alter their behavior to a changing planet. The changes that result are often easy to see.
It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The reason is that different traits have different rates of survival and reproduction (differential fitness) and can be passed from one generation to the next.
In the past, if one particular allele - the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it could quickly become more prevalent than the other alleles. Over time, that would mean the number of black moths within 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 track evolutionary change 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 one strain. Samples from each population were taken regularly and more than 50,000 generations of E.coli have 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 proves that evolution takes time, a fact that many are unable to accept.
Another example of microevolution is how mosquito genes that are resistant to pesticides show up more often in populations in which insecticides are utilized. This is due to the fact that the use of pesticides causes a selective pressure that favors people with resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance, especially in a world shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding the evolution process will help you make better decisions regarding the future of the planet and its inhabitants.