The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science to comprehend the evolution theory and how it can be applied throughout all fields of scientific research.
This site provides a wide range of tools for students, teachers and general readers of evolution. It also includes important video clips 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 an emblem of love and harmony in a variety of cultures. It has numerous practical applications as well, including providing a framework to understand the evolution of species and how they respond to changes in environmental conditions.
The earliest attempts to depict the world of biology focused on the classification of organisms into distinct categories which had been distinguished by their physical and metabolic characteristics1. These methods, which relied on the sampling of different parts of living organisms or on small fragments of their DNA, greatly increased the variety of organisms that could be included in a tree of life2. These trees are mostly populated by eukaryotes and bacteria are largely underrepresented3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have allowed us to represent the Tree of Life in a much more accurate way. Particularly, molecular methods allow us to build trees using sequenced markers like the small subunit ribosomal RNA gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still is waiting to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are often only found in a single sample5. click through the next webpage of all genomes produced an initial 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 thoroughly understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine whether specific habitats require special protection. This information can be utilized in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely useful in conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with potentially important metabolic functions that could be at risk of anthropogenic changes. Although funding to protect biodiversity are crucial however, the most effective method 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 is also known as an evolutionary tree, shows the relationships 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 construct a phylogenetic tree which illustrates 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 ) determines the relationship between organisms with similar traits that have evolved from common ancestral. These shared traits can be analogous, or homologous. Homologous traits are similar in their evolutionary path. Analogous traits might appear like they are however they do not have the same ancestry. Scientists organize similar traits into a grouping referred to as a clade. For instance, all of the organisms in a clade share the characteristic of having amniotic eggs and evolved from a common ancestor which had these eggs. A phylogenetic tree is built by connecting the clades to identify the organisms that are most closely related to each other.
Scientists utilize molecular DNA or RNA data to create a phylogenetic chart that is more precise and detailed. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can use Molecular Data to estimate the evolutionary age of living organisms and discover how many organisms share an ancestor common to all.
The phylogenetic relationships of organisms can be affected by a variety of factors including phenotypic plasticity, a kind of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to one species than to another which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates an amalgamation of homologous and analogous traits in the tree.
Furthermore, phylogenetics may help predict the time and pace of speciation. This information can aid conservation biologists to decide the species they should safeguard from extinction. In the end, it's the preservation of phylogenetic diversity which will lead to an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism would develop according to its own needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of certain traits can result in changes that are passed on to the
In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance, came together to form a contemporary theorizing of evolution. This describes how evolution is triggered by the variations in genes within the population and how these variants change with time due to natural selection. This model, which encompasses mutations, genetic drift as well as gene flow and sexual selection is mathematically described.
Recent discoveries in evolutionary developmental biology have shown how variation can be introduced to a species by mutations, genetic drift and reshuffling of genes during sexual reproduction and the movement between populations. These processes, along with others such as directionally-selected selection and erosion of genes (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time and changes in phenotype (the expression of genotypes within individuals).
Incorporating evolutionary thinking into all areas of biology education can improve student understanding of the concepts of phylogeny as well as evolution. In a recent study by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. For more details on how to teach about evolution, see The Evolutionary Potential in all Areas of Biology or 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 studying living organisms. Evolution is not a past event, but an ongoing process. Bacteria evolve and resist antibiotics, viruses evolve and are able to evade new medications, and animals adapt their behavior in response to the changing climate. The changes that result are often evident.
It wasn't until late 1980s when biologists began to realize that natural selection was also in play. The reason 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 one particular allele - the genetic sequence that defines color in a population of interbreeding organisms, it might quickly become more common than all other alleles. In time, this could mean that the number of black moths within the population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolutionary change when an organism, like bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each population are taken regularly and more than 50,000 generations have now passed.
Lenski's research has revealed that a mutation can dramatically alter the efficiency with which a population reproduces--and so the rate at which it alters. It also proves that evolution takes time--a fact that some people are unable to accept.
Another example of microevolution is that mosquito genes for resistance to pesticides show up more often in populations where insecticides are used. Pesticides create a selective pressure which favors individuals who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance, especially in a world shaped largely by human activity. This includes pollution, climate change, 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.