The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those who are interested in science to understand evolution theory and how it can be applied throughout all fields of scientific research.
This site provides teachers, students and general readers with a wide range of learning resources on evolution. It includes important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is used in many spiritual traditions and cultures as a symbol of unity and love. It also has many practical applications, like providing a framework to understand the evolution of species and how they react to changes in environmental conditions.
The first attempts at depicting the world of biology focused on categorizing organisms into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which depend on the sampling of different parts of organisms or fragments of DNA have significantly increased the diversity of a tree of Life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have enabled us to represent the Tree of Life in a much more accurate way. Particularly, molecular techniques enable us to create trees using sequenced markers, such as the small subunit ribosomal RNA gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are often only found in a single specimen5. A recent analysis of all genomes that are known has produced a rough draft of the Tree of Life, including many bacteria and archaea that have not been isolated, and which are not well understood.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if specific habitats require protection. The information is useful in a variety of ways, including finding new drugs, battling diseases and improving crops. It is also beneficial for conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species with potentially significant metabolic functions that could be at risk of anthropogenic changes. While funding to protect biodiversity are important, the most effective method to protect the world's biodiversity is to empower the people of developing nations with the knowledge they need to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the connections between different groups of organisms. Using molecular data similarities and differences in morphology or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationships between taxonomic groups. The role of phylogeny is crucial in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits can be analogous or homologous. Homologous traits are similar in their evolutionary path. Analogous traits may look similar but they don't have the same origins. Scientists arrange similar traits into a grouping referred to as a the clade. For example, all of the species in a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor who had these eggs. The clades are then linked to form a phylogenetic branch that can determine which organisms have the closest relationship.
To create a more thorough and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to identify the relationships between organisms. This information is more precise than morphological information 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 how many species have an ancestor common to all.
The phylogenetic relationships between species are influenced by many factors, including phenotypic plasticity a type of behavior that changes in response to specific environmental conditions. This can make a trait appear more resembling to one species than another which can obscure the phylogenetic signal. However, this issue can be cured by the use of techniques like cladistics, which incorporate a combination of similar and homologous traits into the tree.
In addition, phylogenetics helps determine the duration and speed of speciation. This information will assist conservation biologists in deciding which species to save from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will create a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms develop different features over time due to their interactions with their surroundings. Many theories of evolution have been proposed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that can be passed onto offspring.
In the 1930s & 1940s, concepts from various fields, including genetics, natural selection, and particulate inheritance, merged to form a contemporary theorizing of evolution. This describes how evolution happens through the variation of genes in a population and how these variants change over time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have shown that variation can be introduced into a species via genetic drift, mutation, and reshuffling genes during sexual reproduction, and also by migration between populations. 에볼루션코리아 , as well as other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution that is defined as change in the genome of the species over time and also the change in phenotype as time passes (the expression of the genotype in the individual).
Incorporating evolutionary thinking into all aspects of biology education can increase students' understanding of phylogeny as well as evolution. A recent study by Grunspan and colleagues, for instance revealed that teaching students 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 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 through looking back--analyzing fossils, comparing species and studying living organisms. Evolution isn't a flims event; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses reinvent themselves and elude new medications, and animals adapt their behavior in response to a changing planet. The resulting changes are often evident.
It wasn't until the late 1980s when biologists began to realize that natural selection was also in play. The key is the fact that different traits result in a different rate of survival and reproduction, and they can be passed down from one generation to the next.
In the past, if one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it could quickly become more common than all other alleles. As 에볼루션 , this could mean that the number of moths with black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each are taken every day and more than fifty thousand generations have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the effectiveness at which a population reproduces. It also demonstrates that evolution is slow-moving, a fact that some find difficult to accept.
Microevolution is also evident in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are used. Pesticides create a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance particularly in a world shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss, which prevents many species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.