The Academy's Evolution Site
Biology is one of the most central concepts in biology. The Academies are committed to helping those who are interested in the sciences comprehend the evolution theory and how it is permeated throughout all fields of scientific research.
This site provides teachers, students and general readers with a wide range of learning resources about evolution. 에볼루션 바카라 무료 contains important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It appears in many cultures and spiritual beliefs as symbolizing unity and love. It has many practical applications as well, including providing a framework to understand the history of species and how they react to changing environmental conditions.
Early approaches to depicting the biological world focused on the classification of organisms into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms, or sequences of short DNA fragments, significantly increased the variety that could be represented in the tree of life2. However these trees are mainly made up of eukaryotes. Bacterial diversity is still largely unrepresented3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. We can construct trees using molecular methods, such as the small-subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate, and are usually found in one sample5. A recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that have not yet been isolated or whose diversity has not been well understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, assisting to determine if specific habitats require special protection. This information can be used in a variety of ways, from identifying the most effective medicines to combating disease to improving crops. It is also valuable for conservation efforts. It can help biologists identify areas most likely to have species that are cryptic, which could perform important metabolic functions, and could be susceptible to human-induced change. While funding to protect biodiversity are essential, the best way to conserve the world's biodiversity is to equip the people of developing nations with the information they require to take action locally and encourage conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the connections between various groups of organisms. Scientists can create an phylogenetic chart which shows the evolutionary relationships between taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestral. These shared traits are either homologous or analogous. Homologous traits are similar in their evolutionary roots, while analogous traits look similar but do not have the same origins. Scientists put similar traits into a grouping called a the clade. All organisms in a group share a characteristic, for example, amniotic egg production. They all came from an ancestor that had these eggs. The clades are then linked to form a phylogenetic branch that can identify organisms that have the closest relationship to.
Scientists utilize DNA or RNA molecular data to build a phylogenetic chart which is more precise and detailed. This information is more precise than the morphological data and gives evidence of the evolutionary history of an individual or group. Molecular data allows researchers to determine the number of organisms that have a common ancestor and to estimate their evolutionary age.
The phylogenetic relationship can be affected by a variety of factors that include phenotypicplasticity. This is a type behaviour that can change in response to specific environmental conditions. This can cause a characteristic to appear more similar to one species than another, clouding the phylogenetic signal. This issue can be cured by using cladistics. This is a method that incorporates an amalgamation of homologous and analogous traits in the tree.
In addition, phylogenetics helps determine the duration and rate at which speciation occurs. This information can aid conservation biologists in making decisions about which species to save from disappearance. It is ultimately the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that a living thing would develop according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy and Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of traits can cause changes that are passed on to the next generation.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection, and particulate inheritance--came together to form the current evolutionary theory, which defines how evolution occurs through the variations of genes within a population and how these variants change in time as a result of natural selection. This model, which is known as genetic drift or mutation, gene flow and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species via mutation, genetic drift, and reshuffling genes during sexual reproduction, and also through migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time), can lead to evolution, which is defined by changes in the genome of the species over time, and also the change in phenotype over time (the expression of the genotype in an individual).
Incorporating evolutionary thinking into all areas of biology education could increase students' understanding of phylogeny and evolution. In a study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution during 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 into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through studying fossils, comparing species, and studying living organisms. But evolution isn't a thing that happened in the past; it's an ongoing process that is taking place in the present. Bacteria evolve and resist antibiotics, viruses re-invent themselves and are able to evade new medications, and animals adapt their behavior to the changing environment. The changes that result are often visible.
It wasn't until late 1980s when biologists began to realize that natural selection was in play. The key is that different traits confer different rates of survival and reproduction (differential fitness) and are passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could be more common than any other allele. As time passes, this could mean that the number of moths sporting black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Observing evolutionary change in action is much easier when a species has a fast generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. The samples of each population were taken regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that a mutation can dramatically alter the efficiency with which a population reproduces--and so the rate at which it changes. It also shows evolution takes time, which is hard for some to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides show up more often in populations where insecticides are used. This is because pesticides cause a selective pressure which favors those who have resistant genotypes.
The speed at which evolution takes place has led to a growing recognition of its importance in a world shaped by human activity--including climate change, pollution and the loss of habitats that prevent the species from adapting. Understanding evolution will assist you in making better choices about the future of the planet and its inhabitants.