The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are involved in helping those who are interested in science to understand evolution theory and how it can be applied across all areas of scientific research.
This site offers a variety of tools for teachers, students, and general readers on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is a symbol of love and unity in many cultures. It also has many practical uses, like providing a framework to understand the history of species and how they respond to changes in the environment.
Early attempts to describe the world of biology were built on categorizing organisms based on their metabolic and physical characteristics. These methods, which rely on sampling of different parts of living organisms or sequences of short fragments of their DNA significantly increased the variety that could be represented in a tree of life2. The trees are mostly composed by eukaryotes, and bacteria are largely underrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to construct trees by using sequenced markers, such as the small subunit ribosomal RNA gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are usually only present in a single specimen5. Recent analysis of all genomes has produced an initial draft of the Tree of Life. This includes a large number of archaea, bacteria and other organisms that have not yet been identified or whose diversity has not been thoroughly understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require special protection. This information can be used in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of the quality of crops. This information is also extremely valuable for conservation efforts. 에볼루션 무료 바카라 can aid biologists in identifying those areas that are most likely contain cryptic species with significant metabolic functions that could be at risk from anthropogenic change. While funds to protect biodiversity are essential, ultimately the best way to preserve the world's biodiversity is for more people in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also called an evolutionary tree) depicts the relationships between organisms. Using molecular data, morphological similarities and differences or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationship between taxonomic groups. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that evolved from common ancestors. These shared traits can be either analogous or homologous. Homologous traits are identical in their evolutionary roots and analogous traits appear similar but do not have the identical origins. Scientists arrange similar traits into a grouping referred to as a clade. For instance, all the organisms that make up a clade share the characteristic of having amniotic egg and evolved from a common ancestor that had eggs. The clades are then linked to create a phylogenetic tree to determine which organisms have the closest relationship.
To create a more thorough and accurate phylogenetic tree, scientists rely on molecular information from DNA or RNA to determine the connections between organisms. This information is more precise than morphological information and gives evidence of the evolutionary background of an organism or group. The use of molecular data lets researchers identify the number of species who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships between organisms can be affected by a variety of factors, including phenotypic plasticity a kind of behavior that changes in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than another, clouding the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics that include a mix of similar and homologous traits into the tree.
Furthermore, phylogenetics may aid in predicting the duration and rate of speciation. This information can assist conservation biologists in deciding which species to save from the threat of extinction. In the end, it's the conservation of phylogenetic variety which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop distinct characteristics over time based on their interactions with their environments. Several theories of evolutionary change have been proposed by a wide 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 requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, came together to create a modern theorizing of evolution. This explains how evolution is triggered by the variation of genes in a population and how these variations change with time due to natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species by mutation, genetic drift, and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as others such as the directional selection process and the erosion of genes (changes in the frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time and changes in phenotype (the expression of genotypes in an individual).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking in all areas of biology. In a study by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution in the course of a college biology. For more information on how to teach about evolution, please read The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through looking back, studying fossils, comparing species and studying living organisms. Evolution is not a past event; it is a process that continues today. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior because of a changing environment. The resulting changes are often evident.
It wasn't until the 1980s when biologists began to realize that natural selection was in action. The reason is that different traits confer different rates of survival and reproduction (differential fitness) and can be 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 all other alleles. Over time, this would mean that the number of moths with black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is much easier when a species has a fast generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from one strain. The samples of each population have been collected regularly, and more than 500.000 generations of E.coli have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the rate of a population's reproduction. It also shows evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is the way mosquito genes that confer resistance to pesticides are more prevalent in areas where insecticides are employed. That's because the use of pesticides causes a selective pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance particularly in a world which is largely shaped by human activities. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding the evolution process can aid you in making better decisions about the future of the planet and its inhabitants.