The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have been active for a long time in helping people who are interested in science understand the theory of evolution and how it influences all areas 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 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 many practical applications, like providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
Early attempts to represent the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, based on the sampling of different parts of living organisms or on sequences of small fragments of their DNA greatly increased the variety of organisms that could be included in a tree of life2. The trees are mostly composed by eukaryotes, and bacterial diversity is vastly underrepresented3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have allowed us to depict the Tree of Life in a much more accurate 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 still a lot of biodiversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are often only represented in a single sample5. A recent study of all genomes that are known has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and which are not well understood.
에볼루션 바카라 사이트 expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine whether specific habitats require special protection. This information can be used in a variety of ways, from identifying new remedies to fight diseases to enhancing the quality of crops. The information is also valuable in conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species with potentially significant metabolic functions that could be at risk from anthropogenic change. Although funding to protect biodiversity are essential but the most effective way to preserve 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 called an evolutionary tree, reveals the relationships between groups of organisms. By using molecular information, morphological similarities and differences, or ontogeny (the course of development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationship between taxonomic groups. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that evolved from common ancestral. These shared traits may be analogous or homologous. Homologous traits are the same in their evolutionary journey. Analogous traits might appear similar but they don't have the same origins. Scientists organize similar traits into a grouping known as a the clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs. They evolved from a common ancestor which had these eggs. The clades are then linked to form a phylogenetic branch to identify organisms that have the closest relationship.
For a more detailed and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships between organisms. This data is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. Researchers can utilize Molecular Data to estimate the age of evolution of organisms and determine the number of organisms that have an ancestor common to all.
Phylogenetic relationships can be affected by a variety of factors, including the phenotypic plasticity. This is a type of behaviour that can change due to unique environmental conditions. This can cause a characteristic to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics that combine homologous and analogous features into the tree.
Additionally, phylogenetics can help determine the duration and rate at which speciation takes place. This information can aid conservation biologists in deciding which species to safeguard from disappearance. In the end, it's the conservation of phylogenetic variety which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to 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 could evolve according to its own requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of traits can lead to 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, were brought together to form a contemporary theorizing of evolution. This explains how evolution occurs by the variation in genes within the population and how these variations alter over time due to natural selection. This model, which incorporates genetic drift, mutations as well as gene flow and sexual selection, can be mathematically described.
Recent advances in evolutionary developmental biology have demonstrated how variations can be introduced to a species through genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with others such as directional selection and gene erosion (changes in frequency of genotypes over time) can result in evolution. Evolution is defined as changes in the genome over time as well as changes in phenotype (the expression of genotypes in individuals).
Students can better understand the concept of phylogeny by using evolutionary thinking in all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance, showed that teaching about the evidence for evolution increased students' acceptance of evolution in a college biology class. To learn more about how to teach about evolution, please see The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally looked at evolution through the past--analyzing fossils and comparing species. They also study living organisms. However, evolution isn't something that occurred in the past; it's an ongoing process, happening in the present. Bacteria mutate and resist antibiotics, viruses reinvent themselves and escape new drugs and animals alter their behavior to a changing planet. The changes that occur are often visible.
However, it wasn't until late 1980s that biologists realized that natural selection can be observed in action as well. The reason 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 group of interbreeding species, it could quickly become more common than other alleles. As time passes, this could mean that the number of moths sporting black pigmentation in a 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 studied twelve populations of E.coli that are descended from one strain. Samples from each population were taken frequently and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can alter the rate of change and the effectiveness at which a population reproduces. It also shows that evolution takes time, which is hard for some to accept.
Microevolution is also evident in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. That's because the use of pesticides causes a selective pressure that favors people with resistant genotypes.
The speed of evolution taking place has led to an increasing appreciation of its importance in a world shaped by human activities, including climate change, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution will help you make better decisions about the future of our planet and its inhabitants.