The Academy's Evolution Site
Biology is a key concept in biology. The Academies have long been involved in helping people who are interested in science comprehend the concept of evolution and how it influences all areas of scientific research.
This site provides a wide range of sources for students, teachers, and general readers on evolution. It has important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of life. It appears in many religions and cultures as an emblem of unity and love. It also has important practical uses, like providing a framework to understand the evolution of species and how they react to changes in the environment.
The earliest attempts to depict the world of biology focused on separating organisms into distinct categories that were identified by their physical and metabolic characteristics1. These methods, which relied on the sampling of various parts of living organisms, or small fragments of their DNA, greatly increased the variety of organisms that could be included in the tree of life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have made it possible to represent the Tree of Life in a much more accurate way. In 무료 에볼루션 , molecular methods allow us to build trees by using sequenced markers such as the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of diversity to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are often only found in a single sample5. A recent analysis of all known genomes has created a rough draft of the Tree of Life, including many archaea and bacteria that have not been isolated, and whose diversity is poorly understood6.
The expanded Tree of Life can be used to determine the diversity of a specific area and determine if particular habitats need special protection. This information can be utilized in a variety of ways, from identifying new remedies to fight diseases to enhancing the quality of crops. This information is also extremely valuable in conservation efforts. It can help biologists identify areas that are likely to have cryptic species, which could have important metabolic functions, and could be susceptible to the effects of human activity. While funds to protect biodiversity are crucial but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be empowered with the knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, reveals the relationships between groups of organisms. Scientists can create a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic groups using molecular data and morphological differences or similarities. Phylogeny plays a crucial role in understanding the relationship between 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 with common traits. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary path. Analogous traits may look similar, but they do not have the same origins. Scientists organize similar traits into a grouping referred to as a Clade. All members of a clade share a trait, such as amniotic egg production. They all evolved from an ancestor that 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 precise and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to identify the relationships between organisms. This information is more precise than the morphological data and provides evidence of the evolution background of an organism or group. The analysis of molecular data can help researchers identify the number of species that share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between species can be affected by a variety of factors, including phenotypic flexibility, a type of behavior that alters in response to unique environmental conditions. This can cause a particular trait to appear more similar in one species than another, clouding the phylogenetic signal. However, this problem can be cured by the use of techniques such as cladistics which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics can help determine the duration and rate at which speciation occurs. This information will assist conservation biologists in making choices about which species to save from the threat of extinction. In the end, it's the conservation of phylogenetic variety that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms change over time due to their interactions with their environment. Many scientists have developed 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 individual needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can cause changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection, and particulate inheritance - came together to form the current evolutionary theory synthesis, which defines how evolution happens through the variation of genes within a population, and how those variations change in time due to natural selection. This model, which is known as genetic drift or mutation, gene flow and sexual selection, is the foundation of modern evolutionary biology and is mathematically described.
Recent advances in the field of 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, in conjunction with other ones like directionally-selected selection and erosion of genes (changes in the frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time and changes in phenotype (the expression of genotypes in an individual).
Students can better understand phylogeny by incorporating evolutionary thinking in all aspects of biology. In a recent study by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. For more details about how to teach evolution read 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 through looking back--analyzing fossils, comparing species, and studying living organisms. But evolution isn't just something that occurred in the past, it's an ongoing process that is taking place right now. Bacteria transform and resist antibiotics, viruses re-invent themselves and escape new drugs and animals change their behavior to the changing environment. The changes that occur are often evident.
It wasn't until late 1980s when biologists began to realize that natural selection was in play. The key is that different traits have different rates of survival and reproduction (differential fitness) and can be passed down from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it might become more common than other allele. In time, this could mean the number of black moths 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 track evolutionary change when an organism, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. The samples of each population have been taken regularly and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the speed 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 that mosquito genes for resistance to pesticides show up more often in populations in which insecticides are utilized. Pesticides create an enticement that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance especially in a planet shaped largely by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding the evolution process can help us make smarter decisions about the future of our planet and the lives of its inhabitants.