The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have long been involved in helping those interested in science understand the theory of evolution and how it influences all areas of scientific research.
This site provides a wide range of sources for teachers, students, and general readers on evolution. It includes important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is a symbol of love and harmony in a variety of cultures. It has many practical applications as well, such as providing a framework to understand the history of species and how they respond to changing environmental conditions.
The first attempts to depict the world of biology were built on categorizing organisms based on their metabolic and physical characteristics. These methods, based on sampling of different parts of living organisms or on small DNA fragments, significantly expanded the diversity that could be included in the tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
By avoiding the need for direct experimentation and observation genetic techniques have allowed us to depict the Tree of Life in a much more accurate way. In particular, molecular methods enable us to create trees using sequenced markers like the small subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of diversity to be discovered. This is especially true for microorganisms that are difficult to cultivate and are typically present in a single sample5. A recent analysis of all known genomes has produced a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and whose diversity is poorly understood6.
The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, which can help to determine whether specific habitats require special protection. The information can be used in a range of ways, from identifying new medicines to combating disease to improving crops. This information is also useful for conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. While funds to safeguard biodiversity are vital however, the most effective method to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, reveals the connections between different groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationship of taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that evolved from common ancestors. These shared traits are either homologous or analogous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look similar but do not have the same origins. Scientists arrange similar traits into a grouping referred to as a clade. For example, all of the organisms that make up a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor which had eggs. The clades are then linked to create a phylogenetic tree to identify organisms that have the closest relationship.
To create a more thorough and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to determine the relationships among organisms. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to calculate the evolutionary age of organisms and identify how many organisms share an ancestor common to all.
The phylogenetic relationship can be affected by a number of factors such as phenotypicplasticity. This is a type of behaviour that can change due to specific environmental conditions. This can cause a trait to appear more resembling to one species than to the other and obscure the phylogenetic signals. This problem can be addressed by using cladistics, which is a an amalgamation of analogous and homologous features in the tree.
In addition, phylogenetics can help predict the time and pace of speciation. This information can assist conservation biologists in making decisions about which species to protect from disappearance. In the end, it's the conservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire various characteristics over time due to their interactions with their surroundings. Many theories of evolution have been developed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits can cause changes that can be passed onto offspring.
In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection and particulate inheritance - came together to form the current evolutionary theory synthesis, which defines how evolution happens through the variations of genes within a population, and how those variants change in time due to natural selection. This model, called genetic drift or mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained.
Recent discoveries in the field of evolutionary developmental biology have shown that genetic variation can be introduced into a species through genetic drift, mutation, and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as others 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 by changes in phenotype as time passes (the expression of the genotype in the individual).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny and evolutionary. In a recent study by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution during an undergraduate biology course. 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 the Concept of Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution through looking back in the past, analyzing fossils and comparing species. They also observe living organisms. Evolution is not a distant moment; it is a process that continues today. Bacteria evolve and resist antibiotics, viruses re-invent themselves and elude new medications, and animals adapt their behavior in response to the changing environment. 무료에볼루션 resulting changes are often easy to see.
However, it wasn't until late-1980s that biologists realized that natural selection can be observed in action as well. 무료에볼루션 is that various traits confer different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past, when one particular allele, the genetic sequence that defines color in a population of interbreeding organisms, it might quickly become more prevalent than other alleles. As time passes, this could mean that the number of moths that have black pigmentation in a 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 evolution when the species, like bacteria, has a high generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples from each population are taken every day and over 50,000 generations have now been observed.
Lenski's research has shown that a mutation can dramatically alter the efficiency with which a population reproduces and, consequently, the rate at which it evolves. It also shows evolution takes time, a fact that is hard for some to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more common in populations where insecticides are used. This is due to the fact that the use of pesticides causes a selective pressure that favors people with resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing appreciation of its importance in a world shaped by human activity, including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding the evolution process will help you make better decisions regarding the future of the planet and its inhabitants.