The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies are involved in helping those who are interested in the sciences comprehend the evolution theory and how it is incorporated in all areas of scientific research.
This site provides a wide range of tools for students, teachers and general readers of evolution. It includes key video clip 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. It is seen in a variety of cultures and spiritual beliefs as an emblem of unity and love. It has many practical applications as well, including providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
The first attempts to depict the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on the sampling of various parts of living organisms or sequences of short fragments of their DNA significantly expanded the diversity that could be included in the tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a more precise manner. We can create trees using molecular techniques, such as the small-subunit ribosomal gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is particularly true for microorganisms, which can be difficult to cultivate and are typically only present in a single sample5. A recent analysis of all genomes has produced an initial draft of the Tree of Life. This includes a variety of archaea, bacteria, and other organisms that haven't yet been identified or whose diversity has not been fully understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine if specific habitats require protection. This information can be used in a variety of ways, including identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely beneficial to conservation efforts. It can help biologists identify areas that are most likely to be home to cryptic species, which could have vital metabolic functions and be vulnerable to changes caused by humans. While funds to protect biodiversity are essential, the best way to conserve the biodiversity of the world is to equip the people of developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between organisms. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationships between taxonomic groups. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestral. These shared traits can be either homologous or analogous. Homologous traits are the same in their evolutionary paths. Analogous traits could appear like they are but they don't share the same origins. Scientists combine similar traits into a grouping called a Clade. For example, all of the species in a clade share the trait of having amniotic egg and evolved from a common ancestor that had eggs. A phylogenetic tree is then constructed by connecting the clades to identify the organisms which are the closest to one another.
Scientists utilize DNA or RNA molecular data to build a phylogenetic chart that is more accurate and detailed. This information is more precise than the morphological data 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.
Phylogenetic relationships can be affected by a number of factors such as the phenotypic plasticity. This is a kind of behavior that changes due to unique environmental conditions. This can cause a particular trait to appear more similar to one species than another, clouding the phylogenetic signal. This problem can be mitigated by using cladistics, which is a a combination of analogous and homologous features in the tree.
In addition, phylogenetics can help predict the time and pace of speciation. This information can aid conservation biologists in making decisions about which species to protect from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will lead to a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms acquire various characteristics over time based on their interactions with their surroundings. 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 develop according to its own requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of certain traits can result in changes that are passed on to the
In the 1930s & 1940s, concepts from various areas, including genetics, natural selection, and particulate inheritance, were brought together to create a modern theorizing of evolution. 에볼루션 무료 바카라 describes how evolution is triggered by the variation in genes within the population and how these variants change with time due to natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection is mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have revealed the ways in which variation can be introduced to a species through genetic drift, mutations and reshuffling of genes during sexual reproduction and migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of a genotype over time) can result in evolution, which is defined by change in the genome of the species over time, and also by changes in phenotype as time passes (the expression of that genotype in the individual).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking in all areas of biology. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence for evolution helped students accept the concept of evolution in a college-level biology class. For more details about how to teach evolution read The Evolutionary Potency 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 by studying fossils, comparing species and studying living organisms. But evolution isn't a thing that happened in the past. It's an ongoing process that is that is taking place right now. Viruses evolve to stay away from new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The results are often apparent.
It wasn't until the late 1980s that biologists began realize that natural selection was also in action. The key is the fact that different traits can confer an individual rate of survival and reproduction, and can be passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could be more prevalent than any other allele. As time passes, this could 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 species has a fast generation turnover, as with bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each are taken regularly and more than 500.000 generations have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the rate at which a population reproduces. It also demonstrates that evolution takes time, a fact that is hard for some to accept.
Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more prevalent in areas that have used insecticides. That's because the use of pesticides causes a selective pressure that favors those who have resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance particularly in a world shaped largely by human activity. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding evolution can help us make better choices about the future of our planet as well as the lives of its inhabitants.