The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies have been for a long time involved in helping those interested in science comprehend the theory of evolution and how it permeates all areas of scientific exploration.
This site provides a wide range of tools for teachers, students, and general readers on evolution. It has important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is a symbol of love and harmony in a variety of cultures. It also has important practical applications, like providing a framework to understand the history of species and how they respond to changing environmental conditions.
Early approaches to depicting the world of biology focused on separating species into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms, or sequences of small DNA fragments, significantly expanded the diversity that could be represented in the tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular techniques allow us to build trees using sequenced markers such as the small subunit ribosomal RNA 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 particularly true for microorganisms, which are difficult to cultivate and are often only present in a single specimen5. Recent analysis of all genomes resulted in a rough draft of the Tree of Life. This includes a variety of bacteria, archaea and other organisms that have not yet been identified or their diversity is not well understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, assisting to determine if certain habitats require special protection. This information can be used in a variety of ways, from identifying the most effective remedies to fight diseases to enhancing the quality of crop yields. This information is also beneficial to conservation efforts. It helps biologists determine the areas most likely to contain cryptic species that could have important metabolic functions that may be vulnerable to anthropogenic change. While funding to protect biodiversity are important, the best method to protect the biodiversity of the world is to equip more people in developing countries with the information they require to take action locally and encourage conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationships between taxonomic groups based on molecular data and morphological similarities or differences. Phylogeny is essential in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that evolved from common ancestors. 에볼루션 바카라 사이트 shared traits can be either analogous or homologous. Homologous traits are similar in their evolutionary roots, while analogous traits look similar, but do not share the same origins. Scientists put similar traits into a grouping referred to as a the clade. Every organism in a group have a common trait, such as amniotic egg production. They all came from an ancestor who had these eggs. A phylogenetic tree is constructed by connecting clades to identify the species who are the closest to each other.
For a more precise and accurate phylogenetic tree scientists use molecular data from DNA or RNA to determine the relationships between organisms. This information is more precise and provides evidence of the evolution of an organism. Researchers can use Molecular Data to calculate the evolutionary age of organisms and identify how many organisms have an ancestor common to all.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic plasticity a kind of behavior that alters in response to specific environmental conditions. This can cause a characteristic to appear more similar to a species than another which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics which combine homologous and analogous features into the tree.
Furthermore, phylogenetics may help predict the length and speed of speciation. This information will assist conservation biologists in deciding which species to safeguard from extinction. It is ultimately the preservation of phylogenetic diversity which will create an ecologically balanced and complete ecosystem.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop different features over time as a result of 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 proposed that a living organism develop gradually according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed on to the offspring.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to form a contemporary evolutionary theory. This explains how evolution happens through the variations in genes within the population, and how these variations change with time due to natural selection. This model, which encompasses genetic drift, mutations in gene flow, and sexual selection, can be mathematically described mathematically.
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, as well as by migration between populations. These processes, in conjunction with other ones like directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time and changes in phenotype (the expression of genotypes in an individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. In a recent study conducted by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. To find out more about how to teach about evolution, read The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species, and observing living organisms. Evolution is not a past event, but a process that continues today. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing world. The results are usually evident.
It wasn't until the late 1980s when biologists began to realize that natural selection was also at work. The key is that various traits have different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it could be more common than any other allele. In time, this could mean that the number of black moths within a population 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 much easier when a species has a rapid turnover of its generation like bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples of each population have been taken regularly and more than 50,000 generations of E.coli have passed.
Lenski's work has demonstrated that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently, the rate at which it evolves. It also shows that evolution is slow-moving, a fact that many are unable to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in populations that have used insecticides. That's because the use of pesticides creates a pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a greater appreciation of its importance especially in a planet shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding the evolution process can help us make better choices about the future of our planet, as well as the lives of its inhabitants.