The Academy's Evolution Site
The concept of biological evolution is among the most central concepts in biology. The Academies have long been involved in helping people who are interested in science comprehend the theory of evolution and how it influences all areas of scientific research.
This site provides students, teachers and general readers with a range of educational resources on evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. 무료 에볼루션 is a symbol of love and harmony in a variety of cultures. It can be used in many practical ways as well, such as providing a framework to understand the evolution 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 relied on sampling of different parts of living organisms or on short fragments of their DNA, significantly increased the variety that could be included in a tree of life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
Genetic techniques have significantly expanded our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular methods enable us to create trees using sequenced markers such as the small subunit ribosomal gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly relevant to microorganisms that are difficult to cultivate and are usually found in a single specimen5. A recent analysis of all genomes produced an unfinished draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that have not yet been isolated or the diversity of which is not well understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine whether specific habitats require protection. The information is useful in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely valuable for conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species that could have important metabolic functions that could be at risk from anthropogenic change. While funds to protect biodiversity are essential, the best method to protect the world's biodiversity is to empower more people in developing countries with the knowledge they need to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, shows the connections between different groups of organisms. Using molecular data similarities and differences in morphology or ontogeny (the process of the development of an organism) scientists can create an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic categories. The role of phylogeny is crucial in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from a common ancestor. These shared traits are either analogous or homologous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look like they do, but don't have the same ancestors. Scientists arrange similar traits into a grouping referred to as a Clade. All members of a clade share a characteristic, for example, amniotic egg production. They all evolved from an ancestor that had these eggs. The clades then join to form a phylogenetic branch to identify organisms that have the closest relationship.
For a more detailed and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships among organisms. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to determine the age of evolution of organisms and determine how many species share a common ancestor.
The phylogenetic relationships of a species can be affected by a number of factors, including the phenotypic plasticity. This is a kind of behavior that changes as a result of particular environmental conditions. This can cause a trait to appear more resembling to one species than another, obscuring the phylogenetic signals. This problem can be mitigated by using cladistics, which incorporates the combination of analogous and homologous features in the tree.
Additionally, phylogenetics can help determine the duration and rate of speciation. This information can aid conservation biologists to make decisions about which species they should protect from extinction. In the end, it's the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme of evolution is that organisms acquire various characteristics over time as a result of their interactions with their environment. Many theories of evolution have been proposed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its needs as well as 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 causes changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection and particulate inheritance - came together to create the modern evolutionary theory synthesis, which defines how evolution occurs through the variation of genes within a population, and how those variations change in time as a result of natural selection. This model, which is known as genetic drift or mutation, gene flow, and sexual selection, is a cornerstone of the current evolutionary biology and is mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that variation can be introduced into a species through mutation, genetic drift, and reshuffling genes during sexual reproduction, as well as through 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 as changes in the genome over time and changes in the phenotype (the expression of genotypes in individuals).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking throughout all aspects 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 during a college-level course in biology. 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 Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back, studying fossils, comparing species and observing living organisms. Evolution isn't a flims moment; it is an ongoing process. Bacteria mutate and resist antibiotics, viruses re-invent themselves and are able to evade new medications, and animals adapt their behavior in response to a changing planet. The results are usually visible.
But it wasn't until the late-1980s that biologists realized that natural selection could be observed in action as well. The reason is that different traits confer different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past when one particular allele - the genetic sequence that determines coloration--appeared in a population of interbreeding species, it could quickly become more common than the other alleles. Over time, that would mean the number of black moths in the population 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 much easier when a species has a rapid turnover of its generation like bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. The samples of each population have been taken regularly and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that mutations can drastically alter the efficiency with the rate at which a population reproduces, and consequently, the rate at which it evolves. It also shows evolution takes time, something that is hard for some to accept.
Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more common in populations where insecticides have been used. This is because pesticides cause an enticement that favors those who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance, especially in a world that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding the evolution process can help you make better decisions about the future of the planet and its inhabitants.