The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it is permeated in all areas of scientific research.
This site provides teachers, students and general readers with a range of learning resources about evolution. It includes the most important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is a symbol of love and unity across many cultures. It has numerous practical applications as well, including providing a framework for understanding the history of species, and how they respond to changing environmental conditions.
Early attempts to describe the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on sampling of different parts of living organisms or small DNA fragments, significantly increased the variety that could be included in a tree of life2. The trees are mostly 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 need for direct observation and experimentation. Trees can be constructed using molecular techniques like the small-subunit ribosomal gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly true for microorganisms, which can be difficult to cultivate and are often only present in a single specimen5. A recent analysis 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.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine if specific habitats require special protection. This information can be utilized in a variety of ways, such as finding new drugs, fighting diseases and improving crops. It is also useful to conservation efforts. It can aid biologists in identifying areas most likely to have cryptic species, which may have vital metabolic functions and are susceptible to changes caused by humans. While funding to protect biodiversity are important, the most effective method to preserve the world's biodiversity is to empower more people in developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny, also called an evolutionary tree, shows the relationships between different groups of organisms. Scientists can create a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic categories using molecular information and morphological differences or similarities. The role of phylogeny is crucial in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits can be homologous, or analogous. Homologous traits are similar in terms of their evolutionary path. Analogous traits might appear like they are however they do not share the same origins. Scientists group similar traits together into a grouping called a clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor that had eggs. The clades are then connected to create a phylogenetic tree to determine the organisms with the closest relationship to.
To create a more thorough and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to establish the relationships among organisms. This data is more precise than morphological data and gives evidence of the evolutionary background of an organism or group. The analysis of molecular data can help researchers determine the number of organisms that share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships between species can be influenced by several factors including phenotypic plasticity, a kind of behavior that changes in response to specific environmental conditions. This can cause a characteristic to appear more similar to a species than to another, obscuring the phylogenetic signals. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous traits in the tree.
Additionally, phylogenetics can help predict the duration and rate at which speciation takes place. This information can aid conservation biologists in making choices about which species to save from extinction. In the end, it's the preservation of phylogenetic diversity that will result in 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. Several theories of evolutionary change have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that could be passed onto offspring.
In the 1930s & 1940s, theories from various fields, including natural selection, genetics & particulate inheritance, came together to form a contemporary synthesis of evolution theory. This describes how evolution happens through the variations in genes within the population, and how these variations change over time as a result of natural selection. This model, which includes mutations, genetic drift in gene flow, and sexual selection can be mathematically described mathematically.
Recent developments in the field of evolutionary developmental biology have shown that variation can be introduced into a species through mutation, genetic drift, and reshuffling 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 the genotype over time) can result in evolution, which is defined by change in the genome of the species over time and also by changes in phenotype over time (the expression of that genotype in the individual).
Students can better understand phylogeny by incorporating evolutionary thinking into all areas of biology. In a recent study by Grunspan et al. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. To learn more about how to teach about evolution, read The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally looked at evolution through the past, studying fossils, and comparing species. They also observe living organisms. Evolution is not a past moment; it is an ongoing process. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. 에볼루션코리아 alter their behavior as a result of a changing environment. The results are usually visible.
However, it wasn't until late 1980s that biologists realized that natural selection could be seen in action, as well. The reason is that different traits confer 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 species, it could rapidly become more common than all other alleles. As time passes, this could mean that the number of moths sporting black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from a single strain. The samples of each population were taken regularly, and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the effectiveness at which a population reproduces. It also demonstrates that evolution takes time, a fact that some people are unable to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in populations that have used insecticides. This is because the use of pesticides creates a selective pressure that favors those with resistant genotypes.
The rapid pace at which evolution takes place has led to an increasing recognition of its importance in a world that is shaped by human activity--including climate changes, pollution and the loss of habitats that hinder many species from adapting. Understanding the evolution process can assist you in making better choices about the future of our planet and its inhabitants.