The Academy's Evolution Site
The concept of biological evolution is among the most central concepts in biology. The Academies are involved in helping those interested in science to comprehend the evolution theory and how it can be applied across all areas of scientific research.
This site provides a wide range of sources for students, teachers as well as general readers about evolution. It has key video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It appears in many spiritual traditions and cultures as symbolizing unity and love. It also has important practical applications, like providing a framework to understand the history of species and how they respond to changes in the environment.
The first attempts to depict the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods rely on the collection of various parts of organisms, or fragments of DNA, have significantly increased the diversity of a Tree of Life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods allow us to construct trees by using sequenced markers such as the small subunit ribosomal RNA gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. 에볼루션사이트 is particularly the case for microorganisms which are difficult to cultivate, and are typically present in a single sample5. A recent analysis of all genomes resulted in a rough draft of a Tree of Life. This includes a wide range of bacteria, archaea and other organisms that haven't yet been identified or the diversity of which is not thoroughly understood6.
The expanded Tree of Life can be used to determine the diversity of a specific region and determine if particular habitats require special protection. This information can be used in a variety of ways, from identifying new remedies to fight diseases to improving crop yields. The information is also beneficial in conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with important metabolic functions that may be at risk of anthropogenic changes. Although funds to safeguard biodiversity are vital, 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 act locally in order to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between organisms. Utilizing molecular data as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism), scientists can build a phylogenetic tree which illustrates the evolution of taxonomic groups. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar traits and evolved from an ancestor with common traits. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary journey. Analogous traits might appear like they are, but they do not have the same origins. Scientists group similar traits into a grouping called a Clade. All members of a clade share a trait, such as amniotic egg production. They all evolved from an ancestor with these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms which are the closest to each other.
Scientists make use of DNA or RNA molecular information to create a phylogenetic chart that is more precise and detailed. This data is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. The analysis of molecular data can help researchers determine the number of species that share the same ancestor and estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors such as the phenomenon of phenotypicplasticity. This is a type behaviour that can change as a result of specific environmental conditions. This can cause a characteristic to appear more similar to one species than another, clouding the phylogenetic signal. This issue can be cured by using cladistics. This is a method that incorporates a combination of homologous and analogous features in the tree.
Additionally, phylogenetics can aid in predicting the duration and rate of speciation. This information can assist conservation biologists make decisions about the species they should safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity which will result in a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have developed 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 individual needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of traits can cause changes that can be passed on to future generations.
In the 1930s & 1940s, ideas from different fields, such as genetics, natural selection, and particulate inheritance, merged to form a contemporary synthesis of evolution theory. This describes how evolution occurs by the variation in genes within a population and how these variations change with time due to natural selection. This model, which encompasses mutations, genetic drift, gene flow and sexual selection can be mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have shown that genetic variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes during sexual reproduction, as well as through the movement of populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution which is defined by change in the genome of the species over time, and the change in phenotype as time passes (the expression of the genotype within the individual).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking in all areas of biology. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. For more information on how to teach about evolution read The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily A Framework for Integrating 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 observe living organisms. Evolution is not a past event; it is an ongoing process. Bacteria evolve and resist antibiotics, viruses re-invent themselves and elude new medications and animals alter their behavior to the changing climate. The results are usually easy to see.
It wasn't until late 1980s that biologists understood that natural selection can be observed in action as well. The key is that various traits have different rates of survival and reproduction (differential fitness) and can be passed 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 quickly become more common than the other alleles. In time, this could mean that the number of moths with black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
The ability to observe evolutionary change is easier when a species has a rapid generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. The samples of each population were taken frequently and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's work has shown that mutations can alter the rate of change and the efficiency at which a population reproduces. It also demonstrates that evolution takes time, something that is difficult for some to accept.
Another example of microevolution is how mosquito genes that are resistant to pesticides appear more frequently in populations where insecticides are used. This is because the use of pesticides creates a pressure that favors those who have resistant genotypes.
The rapidity of evolution has led to a growing awareness of its significance especially in a planet which is largely shaped by human activities. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding evolution can help us make smarter choices about the future of our planet, as well as the life of its inhabitants.