The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies have been active for a long time in helping people who are interested in science understand the concept of evolution and how it influences every area of scientific inquiry.
This site provides teachers, students and general readers with a range of educational resources on evolution. It includes the most important video clips from NOVA and the WGBH-produced science programs on DVD.
에볼루션사이트 of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is a symbol of love and unity across many cultures. It also has practical applications, like providing a framework to understand the history of species and how they respond to changes in the environment.
Early attempts to describe the world of biology were based on categorizing organisms based on their metabolic and physical characteristics. These methods, based on the sampling of different parts of living organisms or on small DNA fragments, greatly increased the variety of organisms that could be included in a tree of life2. However the trees are mostly composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.
Genetic techniques have greatly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. We can construct trees using molecular techniques like the small-subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are often only represented in a single sample5. A recent analysis of all genomes that are known has created a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated, and their diversity is not fully understood6.
This expanded Tree of Life can be used to assess the biodiversity of a specific region and determine if certain habitats need special protection. This information can be used in a variety of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. This information is also extremely beneficial to conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. While funds to protect biodiversity are crucial but the most effective way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, reveals the relationships between different groups of organisms. By using molecular information as well as morphological similarities and distinctions or ontogeny (the process of the development of an organism) scientists can create an phylogenetic tree that demonstrates the evolution of taxonomic categories. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits can be analogous or homologous. Homologous characteristics are identical in terms of their evolutionary path. Analogous traits may look similar however they do not share the same origins. Scientists organize similar traits into a grouping known as a the clade. For example, all of the organisms in a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor that had eggs. The clades then join to create a phylogenetic tree to determine which organisms have the closest relationship.
Scientists use DNA or RNA molecular information to construct a phylogenetic graph that is more accurate and detailed. This information is more precise and provides evidence of the evolution of an organism. Molecular data allows researchers to determine the number of organisms that share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationship can be affected by a number of factors such as the phenomenon of phenotypicplasticity. This is a type of behaviour that can change in response to particular environmental conditions. This can cause a characteristic to appear more resembling to one species than to the other which can obscure the phylogenetic signal. This problem can be addressed by using cladistics, which incorporates an amalgamation of analogous and homologous features in the tree.
Additionally, phylogenetics aids predict the duration and rate of speciation. This information can assist conservation biologists in making decisions about which species to protect from disappearance. In the end, it's the preservation of phylogenetic diversity which will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms alter over time because of their interactions with their environment. Many theories of evolution have been developed by a 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 as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits causes changes that can be passed onto offspring.
In the 1930s and 1940s, concepts from various areas, including natural selection, genetics & particulate inheritance, came together to form a contemporary evolutionary theory. This describes how evolution occurs by the variation in genes within the population and how these variants change with time due to natural selection. This model, which includes genetic drift, mutations, gene flow and sexual selection can be mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that variation can be introduced into a species through mutation, genetic drift, and reshuffling genes during sexual reproduction, and also through the movement of populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of the 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 as time passes (the expression of the genotype within the individual).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking throughout all aspects of biology. In 에볼루션사이트 conducted by Grunspan and co., it was shown that teaching students about the evidence for evolution increased 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 in all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back, studying fossils, comparing species and observing living organisms. But evolution isn't just something that happened in the past; it's an ongoing process, taking place in the present. Bacteria transform and resist antibiotics, viruses re-invent themselves and escape new drugs and animals alter their behavior in response to the changing environment. 에볼루션사이트 that result are often visible.
It wasn't until late-1980s that biologists realized that natural selection could be observed in action as well. The key is that different traits have different rates of survival and reproduction (differential fitness) and are passed down 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 be more common than other allele. Over time, this would mean that the number of moths with black pigmentation may 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 fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from one strain. Samples of each population have been taken frequently and more than 500.000 generations of E.coli have passed.
Lenski's research has shown that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently the rate at which it changes. It also shows evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is the way mosquito genes for resistance to pesticides show up more often in populations in which insecticides are utilized. This is due to pesticides causing an enticement that favors individuals who have resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world shaped largely by human activity. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding evolution will help us make better choices about the future of our planet, and the life of its inhabitants.