The Academy's Evolution Site
Biological evolution is one of the most fundamental concepts in biology. The Academies are committed to helping those who are interested in science understand evolution theory and how it can be applied across all areas of scientific research.
This site provides teachers, students and general readers with a variety of learning resources on evolution. It contains key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of all life. It is a symbol of love and unity in many cultures. It also has important practical uses, like providing a framework to understand the history of species and how they respond to changing environmental conditions.
Early attempts to represent the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods depend on the collection of various parts of organisms or short fragments of DNA have significantly increased the diversity of a Tree of Life2. However these trees are mainly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.
Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. Trees can be constructed using molecular methods like the small-subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are typically only found in a single sample5. A recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a variety of archaea, bacteria, and other organisms that haven't yet been identified or their diversity is not fully understood6.
The expanded Tree of Life can be used to assess the biodiversity of a particular area and determine if specific habitats require special protection. This information can be utilized in a variety of ways, from identifying the most effective remedies to fight diseases to enhancing crop yields. This information is also valuable for conservation efforts. It helps biologists discover areas that are most likely to be home to cryptic species, which may have important metabolic functions and are susceptible to human-induced change. Although funds to protect biodiversity are essential however, the most effective method to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between species. Using molecular data, morphological similarities and differences or ontogeny (the course of development of an organism) scientists can create an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic categories. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms with similar traits and have evolved from an ancestor with common traits. These shared traits could be homologous, or analogous. Homologous traits share their evolutionary origins and analogous traits appear like they do, but don't have the identical origins. Scientists combine similar traits into a grouping known as a the clade. All members of a clade share a characteristic, like amniotic egg production. They all evolved from an ancestor with these eggs. The clades are then connected to form a phylogenetic branch to determine which organisms have the closest relationship.
Scientists use molecular DNA or RNA data 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 determine the number of organisms who share an ancestor common to them and estimate their evolutionary age.
Phylogenetic relationships can be affected by a variety of factors such as phenotypicplasticity. This is a kind of behavior that changes due to specific environmental conditions. This can cause a characteristic to appear more like a species other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics, which incorporates an amalgamation of homologous and analogous traits in the tree.
In addition, phylogenetics helps determine the duration and speed of speciation. This information can aid conservation biologists to decide the species they should safeguard from extinction. Ultimately, it is the preservation of phylogenetic diversity that will result in an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme of evolution is that organisms acquire different features over time due to their interactions with their environments. A variety of theories about evolution have been proposed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs and needs, 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 on to the offspring.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection, and particulate inheritance--came together to form the modern synthesis of evolutionary theory, which defines how evolution is triggered by the variation of genes within a population, and how these variants change over time as a result of natural selection. This model, called genetic drift or mutation, gene flow, and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species via mutation, genetic drift and reshuffling genes during sexual reproduction, and also through the movement of populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to evolution that is defined as change in the genome of the species over time, and also the change in phenotype over time (the expression of the genotype in the individual).
mouse click the up coming post can gain a better understanding of phylogeny by incorporating evolutionary thinking throughout all areas of biology. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution increased students' acceptance of evolution in a college-level biology class. For more details on how to teach evolution, see The Evolutionary Power of Biology 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 by looking back, studying fossils, comparing species and studying living organisms. Evolution is not a distant event; it is a process that continues today. The virus reinvents itself to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing world. The changes that occur are often visible.
It wasn't until the late 1980s when biologists began to realize that natural selection was in play. The key is that various traits have different rates of survival and reproduction (differential fitness), and can be transferred 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 might quickly become more common than other alleles. As time passes, that could 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.
Observing evolutionary change in action is easier when a particular species has a rapid turnover of its generation, as with bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples from each population have been taken regularly, and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently the rate at which it alters. It also demonstrates that evolution takes time, which is difficult for some to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. This is due to pesticides causing an enticement that favors those with resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing recognition of its importance in a world that is shaped by human activity--including climate changes, pollution and the loss of habitats that hinder the species from adapting. Understanding the evolution process will help us make better decisions about the future of our planet, as well as the lives of its inhabitants.