The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have long been involved in helping those interested in science understand the concept of evolution and how it influences all areas of scientific exploration.
This site provides a range of sources for teachers, students, and general readers 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 of the interconnectedness of life. It is seen in a variety of spiritual traditions and cultures as an emblem of unity and love. It also has practical uses, like providing a framework to understand the history of species and how they respond to changes in the environment.
Early attempts to describe the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which depend on the sampling of different parts of organisms or short fragments of DNA have greatly increased the diversity of a Tree of Life2. However the trees are mostly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
In avoiding the necessity of direct observation and experimentation, genetic techniques have allowed us to depict the Tree of Life in a more precise way. Trees can be constructed using molecular techniques such as the small subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much biodiversity to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are usually only found in a single sample5. A recent analysis of all genomes resulted in an unfinished draft of a Tree of Life. This includes a variety of bacteria, archaea and other organisms that haven't yet been isolated, or their diversity is not well understood6.
This expanded Tree of Life can be used to determine the diversity of a particular area and determine if certain habitats need special protection. The information is useful in a variety of ways, including finding new drugs, fighting diseases and improving crops. The information is also useful in conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species with potentially important metabolic functions that may be at risk of anthropogenic changes. Although funds to safeguard biodiversity are vital, ultimately the best way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between different organisms. By using molecular information, morphological similarities and differences or ontogeny (the course of development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationships between taxonomic categories. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar traits and have evolved from a common ancestor. These shared traits can be either analogous or homologous. Homologous traits are similar in terms of their evolutionary paths. Analogous traits might appear similar, but they do not share the same origins. Scientists combine similar traits into a grouping referred to as a clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree can be constructed by connecting clades to determine the organisms who are the closest to each other.
To create a more thorough and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the relationships among organisms. This data is more precise than the morphological data and provides evidence of the evolutionary history of an individual or group. Researchers can utilize Molecular Data to estimate the age of evolution of living organisms and discover the number of organisms that have the same ancestor.
The phylogenetic relationships between species can be affected by a variety of factors including phenotypic plasticity, a type of behavior that changes in response to specific environmental conditions. This can cause a characteristic to appear more resembling to one species than another which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a the combination of homologous and analogous features in the tree.
Additionally, phylogenetics can help determine the duration and rate at which speciation takes place. This information can assist conservation biologists make decisions about which species to protect 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 come up with theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would evolve according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of certain traits can result in changes that are passed on to the next generation.
In the 1930s and 1940s, ideas from different areas, including genetics, natural selection, and particulate inheritance, came together to create a modern theorizing of evolution. This describes how evolution happens through the variations in genes within a population and how these variants change over time as a result of natural selection. This model, known as genetic drift mutation, gene flow and sexual selection, is a key element of modern evolutionary biology and can be mathematically described.
Recent discoveries in evolutionary developmental biology have shown the ways in which variation can be introduced to a species through mutations, genetic drift and reshuffling of genes during sexual reproduction and migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time), can lead to 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 an individual).
Students can better understand phylogeny by incorporating evolutionary thinking throughout all areas of biology. In a recent study conducted by Grunspan and co. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during an undergraduate biology course. To find out more about how to teach about evolution, please look up The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally looked at evolution through the past, analyzing fossils and comparing species. They also observe living organisms. But evolution isn't a thing that happened in the past. It's an ongoing process that is taking place right now. Bacteria transform and resist antibiotics, viruses re-invent themselves and are able to evade new medications and animals change their behavior in response to the changing climate. The changes that result are often evident.
It wasn't until the 1980s that biologists began realize that natural selection was also in play. visit the next internet site is that different traits result in the ability to survive at different rates as well as reproduction, and may be passed on from one generation to another.
In the past when one particular allele--the genetic sequence that defines color in a group of interbreeding organisms, it could rapidly become more common than all other alleles. In time, this could mean the number of black moths in a 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 track evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. Samples of each population have been taken frequently and more than 500.000 generations of E.coli have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time, a fact that many are unable to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in populations that have used insecticides. This is due to pesticides causing an exclusive pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a growing 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 evolution will aid you in making better decisions about the future of the planet and its inhabitants.