The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been for a long time involved in helping those interested in science understand the concept of evolution and how it permeates every area of scientific inquiry.
This site provides teachers, students and general readers with a range of learning resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It is a symbol of love and unity in many cultures. It can be used in many practical ways in addition to 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 depend on the sampling of different parts of organisms, or fragments of DNA have greatly increased the diversity of a tree of Life2. However these trees are mainly made up of eukaryotes. Bacterial diversity remains vastly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods enable us to create trees by using sequenced markers, such as the small subunit of ribosomal RNA gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly true of microorganisms that are difficult to cultivate and are often only represented in a single specimen5. A recent study of all known genomes has produced a rough draft version of the Tree of Life, including a large number of bacteria and archaea that are not isolated and whose diversity is poorly understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine whether specific habitats require special protection. The information is useful in a variety of ways, such as finding new drugs, battling diseases and enhancing crops. The information is also beneficial for conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with significant metabolic functions that could be vulnerable to anthropogenic change. While conservation funds are essential, the best method to preserve the world's biodiversity is to equip more people in developing countries with the information they require to act locally and promote conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) illustrates the relationship between species. Scientists can build an phylogenetic chart which shows the evolution of taxonomic categories using molecular information and morphological differences or similarities. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from a common ancestor. These shared traits may be homologous, or analogous. Homologous traits are the same in terms of their evolutionary path. Analogous traits might appear similar, but they do not share the same origins. Scientists group similar traits into a grouping called a clade. All members of a clade share a characteristic, for example, amniotic egg production. They all derived from an ancestor with these eggs. A phylogenetic tree is constructed by connecting the clades to identify the organisms that are most closely related to each other.
Scientists make use of DNA or RNA molecular data to build a phylogenetic chart that is more accurate and precise. This data is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. Researchers can utilize Molecular Data to estimate the evolutionary age of living organisms and discover how many organisms have the same ancestor.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic flexibility, a type of behavior that alters in response to specific environmental conditions. This can make a trait appear more similar to one species than to the other which can obscure the phylogenetic signal. This issue can be cured by using cladistics, which incorporates an amalgamation of homologous and analogous traits in the tree.
Additionally, phylogenetics aids predict the duration and rate at which speciation takes place. This information can aid conservation biologists to make decisions about the species they should safeguard from extinction. In the end, it's the conservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms develop various characteristics over time based on their interactions with their environments. Many theories of evolution have been proposed by a wide 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, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that can be passed on to the offspring.
In the 1930s and 1940s, ideas from various fields, including natural selection, genetics, and particulate inheritance--came together to form the modern evolutionary theory, which defines how evolution is triggered by the variations of genes within a population, and how those variants change in time due to natural selection. This model, which incorporates genetic drift, mutations in gene flow, and sexual selection can be mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have revealed that variation can be introduced into a species by mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, 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 which is defined by change in the genome of the species over time, and the change in phenotype as time passes (the expression of that genotype in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny and evolution. In a study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution increased their understanding of evolution during the course of a college biology. For more details on how to teach about evolution look up The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have 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 an ongoing process. Bacteria transform and resist antibiotics, viruses evolve 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 the 1980s that biologists began realize that natural selection was in play. The key is that different traits have different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past when one particular allele - the genetic sequence that controls coloration - was present in a population of interbreeding organisms, it might rapidly become more common than other alleles. In 에볼루션 바카라사이트 , 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.
Observing 에볼루션 카지노 사이트 in action is much easier when a species has a fast generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from one strain. Samples of each population were taken frequently and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can drastically alter the rate at which a population reproduces and, consequently the rate at which it alters. It also shows evolution takes time, a fact that is difficult for some to accept.
Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. This is because pesticides cause a selective pressure which favors individuals who have resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing awareness of its significance in a world that is shaped by human activity--including climate change, pollution and the loss of habitats that hinder many species from adapting. Understanding evolution can help us make better decisions about the future of our planet and the lives of its inhabitants.