The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those interested in the sciences comprehend the evolution theory and how it is permeated across all areas of scientific research.
This site provides a range of sources for teachers, students as well as general readers about evolution. It contains key video clips 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 unity across many cultures. It has many practical applications as well, including providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
The earliest attempts to depict the world of biology focused on categorizing organisms into distinct categories which had been identified by their physical and metabolic characteristics1. These methods, which relied on sampling of different parts of living organisms, or sequences of small DNA fragments, significantly increased the variety that could be represented in the tree of life2. The trees are mostly composed by eukaryotes and bacteria are largely underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. We can create trees by using molecular methods, such as the small-subunit ribosomal gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is especially true for microorganisms that are difficult to cultivate, and are usually found in a single specimen5. Recent analysis of all genomes produced a rough draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated, or whose diversity has not been thoroughly understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats need special protection. The information is useful in a variety of ways, including finding new drugs, battling diseases and improving the quality of crops. It is also useful in conservation efforts. 에볼루션 게이밍 helps biologists discover areas most likely to have cryptic species, which could have important metabolic functions and be vulnerable to the effects of human activity. Although funds to protect biodiversity are crucial but the most effective way to protect the world's biodiversity is for more people in developing countries to be empowered with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. Scientists can create a phylogenetic diagram that illustrates the evolutionary relationships between taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny plays a crucial role in understanding the relationship between genetics, biodiversity 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 can be analogous, or homologous. Homologous traits are similar in their evolutionary roots and analogous traits appear like they do, but don't have the same ancestors. Scientists put similar traits into a grouping called a Clade. Every organism in a group have a common characteristic, for example, amniotic egg production. They all derived from an ancestor with these eggs. A phylogenetic tree can be built by connecting the clades to identify the organisms which are the closest to each other.
Scientists utilize molecular DNA or RNA data to build a phylogenetic chart which is more precise and detailed. This data is more precise than the morphological data and gives evidence of the evolutionary background of an organism or group. Molecular data allows researchers to determine the number of species that have an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships between organisms are influenced by many factors, including phenotypic flexibility, a type of behavior that changes in response to specific environmental conditions. This can cause a characteristic to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods such as cladistics that combine similar and homologous traits into the tree.
In addition, phylogenetics can help predict the time and pace of speciation. This information can aid conservation biologists to make decisions about the species they should safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop various characteristics over time due to their interactions with their environment. A variety of theories about evolution have been developed by a wide 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 and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that can be passed on to the offspring.
In the 1930s & 1940s, concepts from various fields, such as genetics, natural selection, and particulate inheritance, merged to form a modern synthesis of evolution theory. This explains how evolution occurs by the variations in genes within the population, and how these variations change over time as a result of natural selection. This model, which encompasses genetic drift, mutations in gene flow, and sexual selection, can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species via mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also through migration between populations. 에볼루션 게이밍 , as well as others 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 as time passes (the expression of the genotype in an individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all areas of biology. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution helped students accept the concept of evolution in a college-level biology class. For more details about how to teach evolution read The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past, analyzing fossils and comparing species. They also observe living organisms. Evolution is not a distant event, but a process that continues today. Bacteria mutate and resist antibiotics, viruses evolve and escape new drugs and animals change their behavior to the changing climate. The resulting changes are often visible.
However, it wasn't until late-1980s that biologists realized that natural selection can be seen in action, as well. The main reason is that different traits confer a different rate of survival as well as reproduction, and may be passed on from one generation to the next.
In the past when one particular allele--the genetic sequence that defines color in a group of interbreeding organisms, it could rapidly become more common than the other alleles. Over time, that would 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 fast generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. The samples of each population have been collected regularly, and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that a mutation can dramatically alter the rate at which a population reproduces--and so the rate at which it evolves. It also shows that evolution is slow-moving, a fact that many are unable to accept.
Microevolution can be observed in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. That's because the use of pesticides causes a selective pressure that favors people with resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance particularly in a world shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding the evolution process will assist you in making better choices regarding the future of the planet and its inhabitants.