The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those who are interested in the sciences understand evolution theory and how it is incorporated across all areas of scientific research.
This site provides a wide range of tools for students, teachers and general readers of evolution. It contains important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and unity in many cultures. It also has important practical uses, like providing a framework for understanding the evolution of species and how they react to changing environmental conditions.
The first attempts at depicting the biological world focused on the classification of species into distinct categories that were distinguished by physical and metabolic characteristics1. 에볼루션 슬롯게임 , which rely on sampling of different parts of living organisms, or sequences of short fragments of their DNA significantly increased the variety that could be included in a tree of life2. These trees are largely composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques enable us to create trees using sequenced markers like the small subunit ribosomal RNA gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly true of microorganisms, which can be difficult to cultivate and are usually only present in a single specimen5. A recent analysis of all genomes produced an initial draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that haven't yet been isolated or their diversity is not thoroughly understood6.
The expanded Tree of Life can be used to assess the biodiversity of a particular area and determine if certain habitats require special protection. This information can be used in many ways, including identifying new drugs, combating diseases and improving the quality of crops. This information is also useful in conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with important metabolic functions that may be at risk of anthropogenic changes. While funds to protect biodiversity are crucial, ultimately the best way to protect the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, shows the connections between groups of organisms. Scientists can build a phylogenetic chart that shows the evolutionary relationships between taxonomic groups using molecular data and morphological differences or similarities. 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 share similar traits that have evolved from common ancestors. These shared traits may be analogous, or homologous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look similar, but do not share the same origins. Scientists put similar traits into a grouping called a the clade. For example, all of the species in a clade share the trait of having amniotic eggs and evolved from a common ancestor that had these eggs. The clades are then connected to create a phylogenetic tree to determine which organisms have the closest connection to each other.
For a more detailed and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships between organisms. This information is more precise than the morphological data and provides evidence of the evolutionary background of an organism or group. The use of molecular data lets researchers identify the number of organisms who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a number of factors that include phenotypicplasticity. This is a type behavior that changes in response to unique environmental conditions. This can make a trait appear more similar to a species than to another, obscuring the phylogenetic signals. However, this issue can be solved through the use of methods like cladistics, which incorporate a combination of similar and homologous traits into the tree.
Furthermore, phylogenetics may help predict the time and pace of speciation. This information will assist conservation biologists in deciding which species to save from extinction. In the end, it is the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire various characteristics over time based on 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 an organism could develop according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of certain traits can result in changes that are passed on to the
In the 1930s & 1940s, concepts from various fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a modern theorizing of evolution. This defines how evolution occurs by the variation of genes in the population and how these 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 a cornerstone of the current evolutionary biology and is mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variations can be introduced into a species via mutation, genetic drift, and reshuffling genes during sexual reproduction, and also by migration between populations. These processes, in conjunction with others, such as directional selection and gene erosion (changes in the frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all aspects of biology education can increase student understanding of the concepts of phylogeny and evolution. A recent study conducted by Grunspan and colleagues, for example demonstrated that teaching about the evidence supporting evolution increased students' acceptance of evolution in a college-level biology course. For more details on how to teach about evolution read The Evolutionary Potency in all Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution by looking back--analyzing fossils, comparing species and observing living organisms. Evolution is not a past event; it is an ongoing process. Bacteria evolve and resist antibiotics, viruses evolve and elude new medications and animals change their behavior in response to a changing planet. The results are usually evident.
It wasn't until late 1980s that biologists understood that natural selection could be seen in action, as well. The key to this is that different traits result in the ability to survive at different rates as well as reproduction, and may be passed on from one generation to another.
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. As time passes, this could mean that the number of moths with black pigmentation in a 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 evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from a single strain. The samples of each population have been collected regularly and more than 500.000 generations of E.coli have passed.
Lenski's research has revealed that mutations can drastically alter the speed at which a population reproduces--and so, the rate at which it changes. It also shows evolution takes time, something that is difficult for some to accept.
Another example of microevolution is the way mosquito genes that confer resistance to pesticides show up more often in areas in which insecticides are utilized. This is due to pesticides causing an exclusive pressure that favors those who have resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing appreciation of its importance in a world shaped by human activities, including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding the evolution process can help us make better decisions regarding the future of our planet as well as the life of its inhabitants.