The Academy's Evolution Site
Biology is one of the most central concepts in biology. The Academies have been active for a long time in helping those interested in science comprehend the theory of evolution and how it permeates every area of scientific inquiry.
This site provides teachers, students and general readers with a wide range of learning resources about 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 all life. our homepage 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 react to changes in environmental conditions.
The first attempts to depict the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on sampling of different parts of living organisms or on short fragments of their DNA greatly increased the variety of organisms that could be included in a tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have allowed us to depict the Tree of Life in a more precise way. Particularly, molecular techniques allow us to construct trees by using sequenced markers like the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much diversity to be discovered. This is especially true for microorganisms that are difficult to cultivate, and which are usually only found in a single specimen5. A recent study of all genomes that are known has created a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and their diversity is not fully understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if particular habitats require special protection. This information can be used in a variety of ways, such as finding new drugs, fighting diseases and improving the quality of crops. our homepage is also extremely beneficial in conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species with potentially significant metabolic functions that could be at risk of anthropogenic changes. Although funds to protect biodiversity are essential, ultimately the best way to protect the world's biodiversity is for more people living in developing countries to be empowered 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 organisms. Scientists can build a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic groups using molecular data and morphological differences or similarities. Phylogeny is crucial in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar traits and evolved from a common ancestor. These shared traits can be homologous, or analogous. Homologous traits are identical in their evolutionary roots, while analogous traits look similar, but do not share the same origins. Scientists put similar traits into a grouping referred to as a Clade. For example, all of the species in a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor that had these eggs. A phylogenetic tree is then constructed by connecting clades to identify the organisms which are the closest 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 determine the evolutionary age of living organisms and discover the number of organisms that share the same ancestor.
The phylogenetic relationships of a species can be affected by a variety of factors, including the phenotypic plasticity. This is a type of behavior that changes due to unique environmental conditions. This can cause a trait to appear more like a species another, obscuring the phylogenetic signal. However, this problem can be solved through the use of methods such as cladistics that combine homologous and analogous features into the tree.
In addition, phylogenetics can aid in predicting the time and pace of speciation. This information can assist conservation biologists decide which species to protect from the threat of 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 develop various characteristics over time as a result of their interactions with their environment. Several theories of evolutionary change have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from a variety of fields--including natural selection, genetics, and particulate inheritance -- came together to form the modern evolutionary theory that explains how evolution happens through the variation of genes within a population, and how these variants change in time due to natural selection. This model, called genetic drift or mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and is mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species through mutation, genetic drift and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of the genotype over time), can lead to evolution that is defined as changes in the genome of the species over time, and also the change in phenotype over time (the expression of that genotype in the individual).
Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolutionary. A recent study 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 look up The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution through looking back in the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a past moment; it is a process that continues today. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior as a result of a changing world. The changes that result are often visible.
It wasn't until the 1980s that biologists began realize that natural selection was also in action. The key is that various traits confer different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past, if one particular allele--the genetic sequence that defines color in a group of interbreeding organisms, it could rapidly become more common than the other alleles. In time, this could mean that the number of black moths within a particular population could rise. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolution when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples from each population were taken frequently and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also shows that evolution takes time, a fact that is hard for some to accept.
Another example of microevolution is the way mosquito genes that are resistant to pesticides appear more frequently in areas where insecticides are employed. This is because pesticides cause a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance particularly in a world shaped largely by human activity. This includes climate change, pollution, and habitat loss that prevents many species from adapting. Understanding evolution can assist you in making better choices about the future of our planet and its inhabitants.