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 comprehend the theory of evolution and how it influences all areas of scientific research.
This site provides students, teachers and general readers with a wide 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 of the interconnectedness of all life. It is an emblem of love and unity across many cultures. It has many practical applications as well, including providing a framework for understanding the history of species and how they respond to changes in environmental conditions.
The earliest attempts to depict the biological world focused on categorizing species into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which rely on the sampling of different parts of organisms or short DNA fragments have significantly increased the diversity of a tree of Life2. The trees are mostly composed of eukaryotes, while bacteria are largely underrepresented3,4.
By avoiding the necessity for direct experimentation and observation genetic techniques have enabled us to depict the Tree of Life in a much more accurate way. Trees can be constructed using molecular techniques such as the small subunit ribosomal gene.
Despite the dramatic growth of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are typically found in a single specimen5. A recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a wide range of archaea, bacteria, and other organisms that have not yet been identified or whose diversity has not been well understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if certain habitats require special protection. The information can be used in a range of ways, from identifying the most effective remedies to fight diseases to improving the quality of crops. This information is also extremely useful to conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species with significant metabolic functions that could be at risk from anthropogenic change. While conservation funds are important, the best way to conserve the world's biodiversity is to equip more people in developing countries with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) depicts the relationships between species. Using molecular data, morphological similarities and differences or ontogeny (the course of development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. Phylogeny is crucial in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from a common ancestor. 에볼루션바카라 shared traits can be either homologous or analogous. Homologous traits are the same in their evolutionary path. Analogous traits may look like they are, but they do not share the same origins. Scientists put similar traits into a grouping referred to as a clade. For example, all of the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor which had eggs. The clades are then connected to create a phylogenetic tree to identify organisms that have the closest connection to each other.
For a more detailed and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships among organisms. This data is more precise than morphological data and provides evidence of the evolution background of an organism or group. The use of molecular data lets researchers identify the number of organisms who share the same ancestor and estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors, including the phenomenon of phenotypicplasticity. This is a kind of behaviour that can change in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than to the other and obscure the phylogenetic signals. However, this problem can be cured by the use of methods such as cladistics which incorporate a combination of homologous and analogous features into the tree.
Additionally, phylogenetics aids determine the duration and rate at which speciation takes place. This information can aid conservation biologists to decide which species to protect from extinction. In the end, it is the preservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop various characteristics over time as a result of their interactions with their environments. A variety of theories about evolution have been developed by a wide variety of scientists such as 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 non-use of traits cause changes that could be passed on to the offspring.
In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection, and particulate inheritance - came together to create the modern evolutionary theory which explains how evolution is triggered by the variations of genes within a population and how those 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 the foundation of current evolutionary biology, and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have shown that variation can be introduced into a species through genetic drift, mutation, and reshuffling of genes in sexual reproduction, as well as through the movement of populations. These processes, as well as others, such as directional selection and gene erosion (changes in the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time as well as changes in the phenotype (the expression of genotypes within individuals).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking throughout all aspects of biology. In a study by Grunspan and colleagues. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during the course of a college biology. For more information on how to teach about evolution, please read 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, studying fossils, and comparing species. They also study living organisms. But 에볼루션 바카라 isn't a thing that happened in the past; it's an ongoing process happening in the present. Bacteria transform and resist antibiotics, viruses re-invent themselves and are able to evade new medications and animals change their behavior in response to the changing climate. The changes that occur are often apparent.
It wasn't until the late 1980s that biologists began realize that natural selection was in action. The key is that different traits confer 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 determines coloration--appeared in a population of interbreeding organisms, it could quickly become more common than all other alleles. Over time, that would mean that the number of black moths in the 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 track evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from a single strain. The samples of each population have been taken frequently and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that a mutation can profoundly alter the efficiency with the rate at which a population reproduces, and consequently, the rate at which it alters. It also proves that evolution takes time--a fact that some people are unable to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are used. 에볼루션 바카라 is because pesticides cause an exclusive pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution can aid you in making better decisions regarding the future of the planet and its inhabitants.