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 the sciences understand evolution theory and how it can be applied in all areas of scientific research.
This site provides teachers, students and general readers with a wide range of educational resources on evolution. It has important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It appears in many spiritual traditions and cultures as a symbol of unity and love. It has numerous practical applications as well, such as providing a framework to understand the history of species, and how they respond to changes in environmental conditions.
The earliest attempts to depict the biological world focused on categorizing organisms into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, which rely on the sampling of different parts of organisms or DNA fragments have significantly increased the diversity of a Tree of Life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods enable us to create trees by using sequenced markers, such as the small subunit ribosomal gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is particularly true of microorganisms, which are difficult to cultivate and are usually only present in a single specimen5. A recent analysis of all genomes produced an unfinished draft of a Tree of Life. This includes a variety of archaea, bacteria and other organisms that have not yet been identified or the diversity of which is not well understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if specific habitats need special protection. The information can be used in a variety of ways, from identifying the most effective remedies to fight diseases to improving the quality of crops. The information is also valuable for conservation efforts. It can help biologists identify areas most likely to have cryptic species, which could have important metabolic functions, and could be susceptible to changes caused by humans. Although funds to protect biodiversity are essential, ultimately the best way to ensure the preservation of biodiversity around the world is for more people in developing countries to be empowered with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny is also known as an evolutionary tree, shows the connections between groups of organisms. Utilizing molecular data similarities and differences in morphology or ontogeny (the course of development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits can be homologous, or analogous. Homologous traits are identical in their evolutionary origins while analogous traits appear similar, but do not share the same ancestors. Scientists organize similar traits into a grouping called a the clade. For example, all of the organisms that make up a clade have the characteristic of having amniotic eggs and evolved from a common ancestor that had eggs. The clades are then linked to form a phylogenetic branch to identify organisms that have the closest relationship.
Scientists utilize DNA or RNA molecular information to create a phylogenetic chart that is more accurate and detailed. This information is more precise and provides evidence of the evolution of an organism. The analysis of molecular data can help researchers identify the number of organisms that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationship can be affected by a number of factors such as phenotypicplasticity. This is a kind of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more similar to one species than another, clouding the phylogenetic signal. However, this issue can be reduced by the use of techniques like cladistics, which include a mix of homologous and analogous features into the tree.
In addition, phylogenetics helps predict the duration and rate of speciation. This information can help conservation biologists make decisions about the species they should safeguard from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will lead to a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms acquire different features over time based on their interactions with their surroundings. Many theories of evolution have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its needs and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits can cause changes that could be passed on to the offspring.
In the 1930s & 1940s, theories from various fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a contemporary theorizing of evolution. This defines how evolution occurs by the variation of genes in the population and how these variants change over time as a result of natural selection. This model, which encompasses 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 shown how variations can be introduced to a species via genetic drift, mutations and reshuffling of genes during sexual reproduction and migration between populations. These processes, in conjunction with other ones like directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes within individuals).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all aspects of biology. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution helped students accept the concept of evolution in a college-level biology class. For more information on how to teach about evolution, see The Evolutionary Potency in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a distant moment; it is an ongoing process. Bacteria transform and resist antibiotics, viruses reinvent themselves and elude new medications and animals change their behavior to the changing environment. The resulting changes are often visible.
However, it wasn't until late 1980s that biologists understood that natural selection can be seen in action, as well. The key is that different characteristics result in different rates of survival and reproduction (differential fitness), and can be passed down from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it might become more common than other allele. Over time, this would mean that the number of moths sporting black pigmentation could 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 rapid generation turnover like bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. 에볼루션게이밍 that descended from a single strain; samples of each population are taken on a regular basis, and over fifty thousand generations have passed.
Lenski's work has demonstrated that mutations can drastically alter the rate at which a population reproduces and, consequently, the rate at which it changes. discover here shows that evolution takes time, which is hard for some to accept.
Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides have been used. This is because pesticides cause a selective pressure which favors those with resistant genotypes.
The rapid pace at which evolution can take place has led to a growing awareness of its significance in a world that is shaped by human activities, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process can help us make smarter decisions regarding the future of our planet and the life of its inhabitants.