The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those who are interested in science to understand evolution theory and how it is incorporated across all areas of scientific research.
This site provides a wide range of sources for teachers, students, and general readers on evolution. It includes key video clip 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 can be used in many practical ways as well, including providing a framework for understanding the history of species, and how they react to changes in environmental conditions.
The first attempts at depicting the biological world focused on the classification of species into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, which relied on the sampling of different parts of living organisms or on sequences of short DNA fragments, greatly increased the variety of organisms that could be included in the tree of life2. These trees are mostly populated by eukaryotes, and the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. We can construct trees by using molecular methods such as the small subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is still a lot of biodiversity to be discovered. This is especially true of microorganisms that are difficult to cultivate and are usually only represented in a single sample5. Recent analysis of all genomes produced a rough draft of a Tree of Life. This includes a variety of archaea, bacteria and other organisms that have not yet been isolated or their diversity is not fully understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine if specific habitats require special protection. This information can be used in a variety of ways, including identifying new drugs, combating diseases and improving the quality of crops. 에볼루션 바카라 체험 is also incredibly useful in conservation efforts. It helps biologists discover areas most likely to be home to cryptic species, which may have important metabolic functions and are susceptible to the effects of human activity. Although funding to safeguard biodiversity are vital, ultimately the best way to ensure the preservation of biodiversity around the world is for more people in developing countries to be equipped with the knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny is also known as an evolutionary tree, shows the connections between groups of organisms. Utilizing molecular data as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationships between taxonomic categories. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits could be analogous, or homologous. Homologous traits are similar in their underlying evolutionary path while analogous traits appear similar, but do not share the same origins. Scientists combine similar traits into a grouping known as a the 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 that had eggs. The clades then join to form a phylogenetic branch that can determine which organisms have the closest relationship.
For a more detailed and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to establish the relationships between organisms. This data is more precise than morphological information and gives evidence of the evolutionary history of an organism or group. The analysis of molecular data can help researchers determine the number of species who share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationship can be affected by a number of factors that include the phenomenon of phenotypicplasticity. This is a type behavior that changes due to unique environmental conditions. This can cause a trait to appear more similar to a species than another and obscure the phylogenetic signals. This issue can be cured by using cladistics, which is a the combination of homologous and analogous features in the tree.
In addition, phylogenetics can aid in predicting the duration and rate of speciation. This information will assist conservation biologists in deciding which species to protect from disappearance. It is ultimately the preservation of phylogenetic diversity that will result in a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. Many scientists have come up with 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 conceived the modern hierarchical system of taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of traits can lead to changes that are passed on to the
In the 1930s and 1940s, theories from various fields, including natural selection, genetics, and particulate inheritance -- came together to create the modern evolutionary theory, which defines how evolution occurs through the variations of genes within a population and how those variations change over time due to natural selection. This model, which is known as genetic drift, mutation, gene flow and sexual selection, is a cornerstone of current evolutionary biology, and can be mathematically explained.
Recent advances in the field of evolutionary developmental biology have revealed how variations can be introduced to a species through mutations, genetic drift and reshuffling of genes during sexual reproduction, and even migration between populations. These processes, as well as others such as the directional selection process and the erosion of genes (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 in individuals).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny as well as evolution. A recent study by Grunspan and colleagues, for instance, showed that teaching about the evidence supporting evolution increased students' understanding of evolution in a college-level biology course. For more details on how to teach evolution read The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily: a Framework for Integrating Evolution into Life Sciences Education.
에볼루션 슬롯 in Action
Traditionally, scientists have studied evolution by studying fossils, comparing species and studying living organisms. Evolution isn't a flims moment; it is an ongoing process that continues to be observed today. Bacteria transform and resist antibiotics, viruses re-invent themselves and escape new drugs, and animals adapt their behavior to the changing environment. The resulting changes are often evident.
However, it wasn't until late 1980s that biologists understood that natural selection can be observed in action as well. The key is the fact that different traits can confer a different rate of survival and reproduction, and can be passed down from generation to generation.
In the past, if one particular allele - the genetic sequence that defines color in a population of interbreeding species, it could rapidly become more common than all other alleles. As time passes, this could mean that the number of moths that have black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolutionary change when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from a single strain. Samples from each population have been collected regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can alter the rate of change and the rate of a population's reproduction. It also demonstrates that evolution takes time--a fact that some people find difficult to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides are more prevalent in areas where insecticides are used. This is because the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.
The speed at which evolution takes place has led to an increasing awareness of its significance in a world that is shaped by human activity--including climate change, pollution and the loss of habitats that prevent many species from adapting. Understanding evolution can help us make better decisions about the future of our planet and the lives of its inhabitants.