The Academy's Evolution Site
Biological evolution is one of the most central concepts in biology. The Academies are committed to helping those who are interested in science comprehend the evolution theory and how it is incorporated throughout all fields of scientific research.
This site provides students, teachers and general readers with a range of learning resources 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 that symbolizes the interconnectedness of life. It is an emblem of love and unity across many cultures. It also has practical applications, like providing a framework for understanding the evolution of species and how they react to changes in the environment.
The first attempts to depict the world of biology were founded on categorizing organisms on their physical and metabolic characteristics. These methods, which depend on the collection of various parts of organisms, or fragments of DNA have greatly increased the diversity of a tree of Life2. These trees are largely composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.
Genetic techniques have greatly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods enable us to create trees using sequenced markers such as the small subunit of ribosomal RNA gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are typically only represented in a single specimen5. Recent analysis of all genomes has produced an unfinished draft of the 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 fully understood6.
This expanded Tree of Life can be used to determine the diversity of a specific region and determine if particular habitats need special protection. The information is useful in many ways, including identifying new drugs, combating diseases and enhancing crops. It is also valuable to conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species that could have significant metabolic functions that could be at risk from anthropogenic change. Although funding to safeguard biodiversity are vital however, the most effective method to protect 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, also known as an evolutionary tree, shows the connections between groups of organisms. Scientists can create a phylogenetic chart that shows the evolution of taxonomic groups using molecular data and morphological similarities or differences. Phylogeny plays a crucial role in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits are either analogous or homologous. Homologous traits are identical in their evolutionary roots, while analogous traits look similar, but do not share the same origins. Scientists organize similar traits into a grouping called a the clade. All members of a clade have a common trait, such as amniotic egg production. They all derived from an ancestor that had these eggs. sneak a peek at this web-site join to form a phylogenetic branch that can determine the organisms with the closest connection to each other.
Scientists utilize DNA or RNA molecular data to construct a phylogenetic graph that is more accurate and precise. This data is more precise than the morphological data and provides evidence of the evolution history of an individual or group. The use of molecular data lets researchers determine the number of species that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationships of organisms can be affected by a variety of factors, including phenotypic flexibility, an aspect of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more similar in one species than another, obscuring the phylogenetic signal. However, this issue can be cured by the use of techniques such as cladistics which incorporate a combination of homologous and analogous features into the tree.
In addition, phylogenetics helps determine the duration and rate of speciation. This information can assist conservation biologists decide which species to protect from the threat of extinction. In the end, it's the conservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have come up with 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, the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of certain traits can result in changes that are passed on to the next generation.
In the 1930s & 1940s, theories from various areas, including genetics, natural selection, and particulate inheritance, came together to form a modern synthesis of evolution theory. This explains how evolution is triggered by the variation in genes within the population, and how these variations change over time as a result of natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is the foundation of modern evolutionary biology and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that variation can be introduced into a species by mutation, genetic drift, and reshuffling genes during sexual reproduction, as well as through the movement of populations. These processes, as well as 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 changes in the genome of the species over time and also the change in phenotype as time passes (the expression of that genotype in an individual).
Incorporating evolutionary thinking into all aspects of biology education can improve students' understanding of phylogeny and evolution. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence for evolution increased students' understanding of evolution in a college biology course. To find out more about how to teach about evolution, look up The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past--analyzing fossils and comparing species. They also observe living organisms. But evolution isn't just something that happened in the past, it's an ongoing process, taking place today. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior in the wake of a changing environment. The results are often evident.
It wasn't until late-1980s that biologists realized that natural selection can be seen in action, as well. The key is that various traits confer different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past, when one particular allele - the genetic sequence that determines coloration--appeared in a group of interbreeding organisms, it might rapidly become more common than the other alleles. As time passes, that 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 track evolutionary change when the species, 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 are taken every day, and over 500.000 generations have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the efficiency at which a population reproduces. It also shows that evolution takes time--a fact that some are unable to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides are more prevalent in populations in which insecticides are utilized. This is because pesticides cause a selective pressure which favors those with resistant genotypes.
The rapidity of evolution has led to an increasing recognition of its importance, especially in a world which is largely shaped by human activities. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution can help us make better decisions about the future of our planet and the life of its inhabitants.