The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have been for a long time involved in helping those interested in science comprehend the theory of evolution and how it permeates all areas of scientific research.
This site provides students, teachers and general readers with a variety of learning resources about evolution. It includes key video clip 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 can be used in many practical ways in addition to providing a framework for understanding the history of species, and how they react to changes in environmental conditions.
The first attempts to depict the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, which relied on sampling of different parts of living organisms, or short fragments of their DNA, significantly increased the variety that could be represented in the tree of life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
By avoiding the necessity for direct experimentation and observation, genetic techniques have made it possible to depict the Tree of Life in a more precise way. Particularly, molecular techniques allow us to construct trees using sequenced markers, such as the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of diversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are typically only present in a single sample5. A recent study of all known genomes has created a rough draft of the Tree of Life, including many bacteria and archaea that are not isolated and their diversity is not fully understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a particular area and determine if specific habitats require special protection. This information can be used in many ways, including finding new drugs, battling diseases and improving crops. This information is also extremely useful in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. While funds to protect biodiversity are important, the best way to conserve the biodiversity of the world is to equip the people of developing nations with the knowledge they need to act locally and promote conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, shows the connections between groups of organisms. By using molecular information similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits are either homologous or analogous. Homologous traits share their underlying evolutionary path, while analogous traits look like they do, but don't have the same origins. Scientists put similar traits into a grouping called a the clade. For instance, all of the organisms that make up a clade have the characteristic of having amniotic egg and evolved from a common ancestor that had eggs. The clades are then connected to form a phylogenetic branch to determine which organisms have the closest relationship to.
Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more precise and precise. This information is more precise than morphological information and provides evidence of the evolutionary history of an individual or group. The use of molecular data lets researchers determine the number of species that share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic plasticity a kind of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more like a species other species, which can obscure the phylogenetic signal. However, this problem can be reduced by the use of methods such as cladistics which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics can help determine the duration and speed at which speciation occurs. click the next web page can help conservation biologists decide 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 change over time due to their interactions with their environment. Many theories of evolution have been proposed by a wide range of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that could be passed on to offspring.
In the 1930s & 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, merged to form a modern synthesis of evolution theory. This explains how evolution happens through the variations in genes within a population and how these variants alter over time due to natural selection. This model, which incorporates mutations, genetic drift in gene flow, and sexual selection is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variation can be introduced into a species by mutation, genetic drift, and reshuffling genes during sexual reproduction, and also by migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of an individual's 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 within the individual).
Incorporating evolutionary thinking into all areas of biology education could increase student understanding of the concepts of phylogeny and evolution. In a recent study conducted by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution increased their acceptance of evolution during the course of a college biology. For more details about how to teach evolution read The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past--analyzing fossils and comparing species. They also study living organisms. Evolution isn't a flims event, but an ongoing process that continues to be observed today. 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 results are often apparent.
It wasn't until the late 1980s when biologists began to realize that natural selection was also in play. The key is that different traits confer 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 species, it could quickly become more common than all other alleles. In time, this could mean that the number of moths that have black pigmentation 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 evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples of each are taken on a regular basis and over 500.000 generations have passed.
Lenski's research has shown that a mutation can dramatically alter the rate at the rate at which a population reproduces, and consequently the rate at which it alters. This Internet page demonstrates that evolution is slow-moving, a fact that many are unable to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides appear more frequently in areas where insecticides are employed. Pesticides create an exclusive pressure that favors those with resistant genotypes.
This Internet page of evolution has led to an increasing appreciation of its importance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution can aid you in making better decisions regarding the future of the planet and its inhabitants.