The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are involved in helping those who are interested in the sciences comprehend the evolution theory and how it can be applied across all areas of scientific research.
This site provides a range of resources for students, teachers, and general readers on evolution. It has important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of all life. It is a symbol of love and unity across many cultures. It has numerous practical applications in addition to providing a framework to understand the history of species, and how they react to changes in environmental conditions.
Early approaches to depicting the world of biology focused on separating organisms into distinct categories that were distinguished by their physical and metabolic characteristics1. These methods, which depend on the collection of various parts of organisms or short DNA fragments, have significantly increased the diversity of a Tree of Life2. However these trees are mainly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.
Genetic techniques have greatly expanded our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to build trees using sequenced markers like the small subunit ribosomal RNA gene.
The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much diversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are typically only found in a single specimen5. A recent analysis of all genomes known to date has produced a rough draft version of the Tree of Life, including many archaea and bacteria that have not been isolated, and their diversity is not fully understood6.
The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine if certain habitats require protection. The information is useful in many ways, including identifying new drugs, combating diseases and enhancing crops. This information is also extremely valuable in conservation efforts. It helps biologists discover areas most likely to be home to cryptic species, which may perform important metabolic functions, and could be susceptible to human-induced change. Although funding to protect biodiversity are crucial 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 is also known as an evolutionary tree, shows the connections between different groups of organisms. Using molecular data as well as morphological similarities and distinctions or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationship between taxonomic categories. Phylogeny is crucial in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and have evolved from a common ancestor. These shared traits can be either analogous or homologous. Homologous traits are identical in their evolutionary origins and analogous traits appear similar, but do not share the same ancestors. Scientists organize similar traits into a grouping referred to as a Clade. All members of a clade have a common characteristic, for example, amniotic egg production. They all derived from an ancestor that had these eggs. The clades then join to create a phylogenetic tree to identify organisms that have the closest connection to each other.
For a more precise and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to establish the relationships among organisms. This information is more precise than morphological data and provides evidence of the evolution history of an organism or group. Researchers can use Molecular Data to determine the evolutionary age of living organisms and discover the number of organisms that have an ancestor common to all.
The phylogenetic relationship can be affected by a variety of factors such as phenotypicplasticity. This is a kind of behaviour that can change as a result of particular environmental conditions. 에볼루션 룰렛 evolutionkr can cause a characteristic to appear more like a species another, obscuring the phylogenetic signal. However, this issue can be reduced by the use of methods such as cladistics that combine analogous and homologous features into the tree.
Furthermore, phylogenetics may aid in predicting the time and pace of speciation. This information can help conservation biologists make decisions about the species they should safeguard from the threat of extinction. It is ultimately the preservation of phylogenetic diversity that will create an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms alter over time because 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 could develop according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy and Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that are passed on to the next generation.
In the 1930s & 1940s, ideas from different fields, including genetics, natural selection, and particulate inheritance, merged to form a modern theorizing of evolution. This describes how evolution happens through the variation of genes in a 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 the foundation of current evolutionary biology, and can be mathematically explained.
Recent discoveries in the field of evolutionary developmental biology have shown that variations can be introduced into a species via genetic drift, mutation, and reshuffling genes during sexual reproduction, as well as through the movement of populations. These processes, along with others such as the directional selection process and the erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time and changes in the phenotype (the expression of genotypes within individuals).
Incorporating evolutionary thinking into all areas of biology education can improve student understanding of the concepts of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence for evolution increased students' acceptance of evolution in a college biology class. To find out more about how to teach about evolution, please read The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past--analyzing fossils and comparing species. They also study living organisms. Evolution is not a past event, but a process that continues today. The virus reinvents itself to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior in the wake of the changing environment. The changes that result are often visible.
But it wasn't until the 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 are passed down from one generation to the next.
In the past, if one particular allele--the genetic sequence that defines color in a population of interbreeding species, it could quickly become more prevalent than other alleles. In time, this 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 observe evolutionary change when the species, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from one strain. The samples of each population have been collected regularly, 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 at which change occurs and the effectiveness of a population's reproduction. It also demonstrates that evolution takes time--a fact that some people find hard to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in areas that have used insecticides. This is because pesticides cause a selective pressure which favors individuals who have resistant genotypes.
The speed at which evolution can take place has led to a growing recognition of its importance in a world shaped by human activities, including climate changes, pollution and the loss of habitats that prevent many species from adapting. Understanding evolution will help you make better decisions about the future of our planet and its inhabitants.