The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been active for a long time in helping those interested in science comprehend the theory of evolution and how it permeates all areas of scientific exploration.
This site provides a wide range of tools for teachers, students as well as general readers about evolution. It contains important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is an emblem of love and unity in many cultures. It can be used in many practical ways as well, such as providing a framework for understanding the history of species and how they react to changing environmental conditions.
The earliest attempts to depict the biological world focused on the classification of organisms into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, which relied on the sampling of different parts of living organisms, or small fragments of their DNA greatly increased the variety of organisms that could be represented in a tree of life2. The trees are mostly composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.
By avoiding the necessity for direct experimentation and observation genetic techniques have enabled us to represent the Tree of Life in a much more accurate way. In particular, molecular methods allow us to build trees by using sequenced markers like the small subunit ribosomal RNA 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 particularly true of microorganisms, which can be difficult to cultivate and are usually only present in a single sample5. A recent study of all genomes known to date has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and their diversity is not fully understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine if certain habitats require protection. This information can be utilized in many ways, including identifying new drugs, combating diseases and improving crops. It is also valuable to conservation efforts. It can aid biologists in identifying areas most likely to be home to species that are cryptic, which could have important metabolic functions, and could be susceptible to the effects of human activity. While conservation funds are essential, the best method to protect the world's biodiversity is to equip more people in developing countries with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between different organisms. Utilizing molecular data, morphological similarities and differences, or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationship between taxonomic groups. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits can be either analogous or homologous. Homologous traits share their evolutionary roots while analogous traits appear similar but do not have the identical origins. Scientists organize similar traits into a grouping known as a clade. All organisms in a group share a characteristic, for example, amniotic egg production. They all evolved from an ancestor that had these eggs. A phylogenetic tree is then constructed by connecting clades to determine the organisms that are most closely related to one another.
Scientists make use of molecular DNA or RNA data to create a phylogenetic chart that is more precise and detailed. This information is more precise and provides evidence of the evolutionary history of an organism. The analysis of molecular data can help researchers identify the number of species who share the same ancestor and 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 changes in response to unique environmental conditions. 에볼루션 바카라 사이트 can cause a characteristic to appear more similar in one species than other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics, which is a a combination of homologous and analogous features in the tree.
Additionally, phylogenetics can help predict the duration and rate at which speciation takes place. This information will assist conservation biologists in deciding which species to save from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will result in a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would develop according to its own requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern hierarchical system of taxonomy and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of traits can lead to changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This explains how evolution happens through the variation of genes in a population and how these variations alter over time due to natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is a key element of modern evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have revealed how variation can be introduced to a species through genetic drift, mutations, reshuffling genes during sexual reproduction, and even migration between populations. These processes, as well as others such as directional selection and gene erosion (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 the phenotype (the expression of genotypes in an individual).
Students can better understand the concept of phylogeny by using evolutionary thinking throughout all areas of biology. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution increased students' understanding of evolution in a college-level biology course. For more information on how to teach about evolution look up The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily as a Framework for Integrating 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 observe living organisms. But evolution isn't just something that happened in the past, it's an ongoing process, happening today. Bacteria mutate and resist antibiotics, viruses re-invent themselves and are able to evade new medications and animals change their behavior to a changing planet. The changes that result are often evident.
It wasn't until late 1980s that biologists began to realize that natural selection was at work. The reason is that different traits have different rates of survival and reproduction (differential fitness) and are passed down from one generation to the next.
In the past, when one particular allele--the genetic sequence that defines color in a group of interbreeding organisms, it could quickly become more common than the other alleles. Over time, this would mean that the number of moths with black pigmentation 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 particular species has a rapid generation turnover such as bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples from each population are taken on a regular basis and more than 50,000 generations have now passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time, a fact that some find difficult to accept.
Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides are used. This is due to pesticides causing an enticement that favors those with resistant genotypes.
The rapid pace of evolution taking place has led to an increasing recognition of its importance in a world that is shaped by human activity, including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding evolution can assist you in making better choices about the future of the planet and its inhabitants.