The Academy's Evolution Site
Biological evolution is one of the most central concepts in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it can be applied across all areas of scientific research.
This site provides a range of resources for teachers, students and general readers of evolution. It has the most important video clips 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 appears in many religions and cultures as symbolizing unity and love. 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.
Early attempts to describe the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, which are based on the collection of various parts of organisms or DNA fragments, have greatly increased the diversity of a Tree of Life2. These trees are mostly populated of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to build trees by using sequenced markers such as the small subunit of ribosomal RNA gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is a lot of biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually only represented in a single specimen5. A recent analysis of all genomes that are known has produced a rough draft of the Tree of Life, including many archaea and bacteria that are not isolated and their diversity is not fully understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if certain habitats require protection. This information can be used in a variety of ways, from identifying the most effective medicines to combating disease to improving crops. The information is also useful for conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with important metabolic functions that could be vulnerable to anthropogenic change. While conservation funds are essential, the best way to conserve the world's biodiversity is to equip the people of developing nations with the knowledge they need to act locally and support conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between different organisms. By using molecular information, morphological similarities and differences, or ontogeny (the course of development of an organism), scientists can build an phylogenetic tree that demonstrates the evolution of taxonomic categories. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that evolved from common ancestors. These shared traits could be either homologous or analogous. Homologous traits are similar in their evolutionary origins, while analogous traits look similar, but do not share the identical origins. Scientists arrange similar traits into a grouping called a clade. All members of a clade share a characteristic, like amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms which are the closest to one another.
Scientists utilize molecular DNA or RNA data to construct a phylogenetic graph that is more precise and precise. This information is more precise and gives evidence of the evolution of an organism. 에볼루션 바카라 체험 can utilize Molecular Data to determine the evolutionary age of living organisms and discover how many species share an ancestor common to all.
The phylogenetic relationships between species can be influenced by several factors, including phenotypic flexibility, an aspect of behavior that alters in response to unique 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 is a an amalgamation of analogous and homologous features in the tree.
In addition, phylogenetics helps predict the duration and rate of speciation. This information will assist conservation biologists in making choices about which species to save from disappearance. Ultimately, it is the preservation of phylogenetic diversity which will lead to a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms change over time due to their interactions with their environment. Many scientists have developed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would develop according to its own needs and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical as well as Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of traits can lead to changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection, and particulate inheritance -- came together to form the current synthesis of evolutionary theory which explains how evolution happens through the variations of genes within a population, and how those variations change over time due to natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection can be mathematically described.
Recent developments in evolutionary developmental biology have shown how variation can be introduced to a species by genetic drift, mutations, reshuffling genes during sexual reproduction, and even migration between populations. These processes, along with others such as directional selection or 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 an individual).
Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolutionary. In a study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution increased their acceptance of evolution during a college-level course in biology. For more information on how to teach about evolution, look up The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by studying fossils, comparing species and studying living organisms. However, evolution isn't something that occurred in the past, it's an ongoing process, that is taking place right now. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior in the wake of a changing world. The changes that occur are often evident.
It wasn't until late 1980s when biologists began to realize that natural selection was in action. The main reason is that different traits confer an individual rate of survival as well as reproduction, and may be passed on from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour - was found in a group of organisms that interbred, it could become more prevalent than any other allele. In time, this could mean the number of black moths in a particular population could rise. 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 rapid generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. Samples from each population have been taken regularly and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that mutations can drastically alter the rate at which a population reproduces and, consequently, the rate at which it evolves. It also shows evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is that mosquito genes for resistance to pesticides show up more often in areas in which insecticides are utilized. This is due to the fact that the use of pesticides causes a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance particularly in a world shaped largely by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution will help us make better decisions about the future of our planet, and the life of its inhabitants.