The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been active for a long time in helping those interested in science understand the concept of evolution and how it affects all areas of scientific research.
This site provides students, teachers and general readers with a range of learning resources about evolution. It has important video clips from NOVA and WGBH's 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 religions and cultures as an emblem of unity and love. It has numerous practical applications as well, such as 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 based on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on sampling of different parts of living organisms, or sequences of short fragments of their DNA significantly increased the variety that could be represented in the tree of life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
By avoiding the necessity for direct experimentation and observation genetic techniques have made it possible to depict the Tree of Life in a more precise manner. Particularly, molecular techniques allow us to build trees using sequenced markers such as the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of biodiversity to be discovered. This is especially true of microorganisms that are difficult to cultivate and are often only present in a single sample5. A recent analysis of all genomes that are known has produced a rough draft version of the Tree of Life, including a large number of archaea and bacteria that are not isolated and which are not well understood.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine whether specific habitats require protection. This information can be utilized in a variety of ways, such as finding new drugs, battling diseases and improving crops. It is also valuable for conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. While funding to protect biodiversity are important, the most effective method to protect the world's biodiversity is to empower more people in developing countries with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the relationships between groups of organisms. Scientists can create a phylogenetic chart that shows the evolutionary relationships between taxonomic groups using molecular data and morphological similarities or differences. 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 with similar characteristics and have evolved from an ancestor that shared traits. These shared traits can be analogous, or homologous. Homologous traits are similar in terms of their evolutionary path. Analogous traits could appear like they are, but they do not share the same origins. Scientists group similar traits into a grouping known as a clade. For instance, all the organisms in a clade share the characteristic of having amniotic egg and evolved from a common ancestor that had these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms that are most closely related to one another.
For a more detailed and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships among organisms. 에볼루션 바카라 무료체험 is more precise than the morphological data and provides evidence of the evolution history of an individual or group. The use of molecular data lets researchers determine the number of species that have an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a number of factors such as the phenotypic plasticity. This is a kind of behavior that alters as a result of specific environmental conditions. This can cause a particular trait to appear more similar to one species than another, obscuring the phylogenetic signal. This problem can be mitigated by using cladistics, which incorporates a combination of analogous and homologous features in the tree.
In addition, phylogenetics helps determine the duration and speed at which speciation takes place. This information can assist conservation biologists in making decisions about which species to safeguard from disappearance. It is ultimately the preservation of phylogenetic diversity which will create a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire distinct characteristics over time as a result of their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism could evolve according to its individual needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of certain traits can result in changes that are passed on to the next generation.
In the 1930s & 1940s, theories from various fields, including natural selection, genetics & particulate inheritance, came together to form a contemporary evolutionary theory. This defines how evolution is triggered by the variation in genes within the population and how these variants change over time as a result of natural selection. This model, which includes genetic drift, mutations in gene flow, and sexual selection, can be mathematically described mathematically.
Recent developments in the field of evolutionary developmental biology have revealed that variations can be introduced into a species through mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also through migration between populations. These processes, along with other ones like directionally-selected selection and erosion of genes (changes in the 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 within individuals).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking throughout all areas of biology. A recent study conducted by Grunspan and colleagues, for example demonstrated that teaching about the evidence for evolution increased students' acceptance of evolution in a college-level biology course. For more details on how to teach about evolution look up The Evolutionary Potency in all Areas of Biology or 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. But evolution isn't just something that happened in the past; it's an ongoing process taking place in the present. Bacteria transform and resist antibiotics, viruses re-invent themselves and are able to evade new medications and animals alter their behavior in response to a changing planet. The changes that occur are often apparent.
It wasn't until late 1980s that biologists began to realize that natural selection was also in play. The main reason is that different traits confer a different rate of survival as well as reproduction, and may be passed on 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 could rapidly become more common than the other alleles. As time passes, this could mean that the number of moths sporting black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is easier when a particular species has a fast generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from one 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 demonstrated that a mutation can profoundly alter the speed at which a population reproduces and, consequently the rate at which it changes. It also demonstrates that evolution takes time, something that is difficult for some to accept.
Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more common in populations that have used insecticides. Pesticides create a selective pressure which favors those who have resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance particularly in a world that is largely shaped by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding evolution can help us make better decisions regarding the future of our planet and the life of its inhabitants.