The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those interested in the sciences learn about the theory of evolution and how it is permeated in all areas of scientific research.
This site provides a range of sources for students, teachers and general readers of evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It appears in many religions and cultures as an emblem of unity and love. It also has important practical applications, such as providing a framework to understand the history of species and how they respond to changes in environmental conditions.
Early attempts to represent the biological world were built on categorizing organisms based on their metabolic and physical characteristics. These methods are based on the sampling of different parts of organisms, or fragments of DNA, have greatly increased the diversity of a Tree of Life2. These trees are mostly populated of eukaryotes, while bacteria are largely underrepresented3,4.
By avoiding the need for direct experimentation and observation genetic techniques have allowed us to represent the Tree of Life in a more precise way. Particularly, molecular techniques allow us to construct trees by using sequenced markers such as the small subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly the case for microorganisms which are difficult to cultivate, and are usually found in a single specimen5. A recent analysis of all genomes resulted in an initial draft of a Tree of Life. This includes a wide range of archaea, bacteria, and other organisms that haven't yet been isolated, or the diversity of which is not well understood6.
This expanded Tree of Life can be used to determine the diversity of a particular area and determine if particular habitats need special protection. This information can be utilized in a variety of ways, such as finding new drugs, fighting diseases and enhancing crops. The information is also incredibly beneficial to conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species that could have significant metabolic functions that could be at risk of anthropogenic changes. Although funding to protect 에볼루션카지노 are essential but the most effective way to protect the world's biodiversity is for more people 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, shows the relationships between different groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. 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 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits can be analogous or homologous. Homologous characteristics are identical in terms of their evolutionary paths. Analogous traits may look like they are but they don't have the same origins. Scientists group similar traits into a grouping called a the clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree is then built by connecting the clades to identify the organisms that are most closely related to each other.
For a more precise and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to identify the connections between organisms. This information is more precise and gives evidence of the evolution of an organism. The use of molecular data lets researchers identify the number of species 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 flexibility, a kind of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more similar to a species than to another and obscure the phylogenetic signals. This problem can be mitigated by using cladistics, which is a the combination of homologous and analogous traits in the tree.
In addition, phylogenetics helps determine the duration and rate at which speciation occurs. This information will assist conservation biologists in deciding which species to save from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will create an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been developed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that can be passed on to the offspring.
In the 1930s & 1940s, ideas from different fields, including genetics, natural selection, and particulate inheritance, merged to create a modern synthesis of evolution theory. This defines how evolution happens through the variations in genes within the population, and how these variants change with time due to natural selection. This model, which is known as genetic drift mutation, gene flow and sexual selection, is a key element of current evolutionary biology, and can be mathematically described.
Recent discoveries in evolutionary developmental biology have revealed how variations can be introduced to a species via mutations, genetic drift and reshuffling of genes during sexual reproduction and the movement between populations. These processes, in conjunction with others, such as directionally-selected selection and erosion of genes (changes in frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence for evolution increased students' understanding of evolution in a college-level biology class. To learn more about how to teach about evolution, look up The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution by looking back--analyzing fossils, comparing species and observing living organisms. Evolution is not a past event, but a process that continues today. Bacteria evolve and resist antibiotics, viruses evolve and escape new drugs and animals alter their behavior in response to a changing planet. The changes that result are often visible.
It wasn't until late 1980s that biologists realized that natural selection can be observed in action as well. The main reason is that different traits confer a different rate of survival as well as reproduction, and may be passed down from one generation to the next.
In the past, when one particular allele - the genetic sequence that defines color in a group of interbreeding organisms, it might rapidly become more common than all other alleles. In time, this could mean that the number of moths sporting 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.
Observing evolutionary change in action is easier when a species has a rapid turnover of its generation such as bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples of each population are taken every day and over fifty thousand generations have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the rate of a population's reproduction. It also proves that evolution takes time, a fact that many are unable to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides appear more frequently in areas in which insecticides are utilized. This is because the use of pesticides creates a pressure that favors people with resistant genotypes.
The rapid pace at which evolution takes place has led to a growing appreciation of its importance in a world shaped by human activity--including climate change, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process will aid you in making better decisions regarding the future of the planet and its inhabitants.