Athens Independent School District is a public school district based in Athens, Texas , United States. The district serves central Henderson County , and small portions of southern Van Zandt and northern Anderson counties. As of November 2020, it served three thousand students.
101-417: In 2018, the district's board of directors decided to move to a four day week, as a means of attracting staff when they did not have the budgets to pay teachers what other districts could. The four day week became effective in fall 2019. This was initially a provisional move for a three year period, but the district decided to make it the standard schedule in 2022. Circa 2022 various groups expressed support for
202-593: A Chief of School Safety and Security within the Texas Education Agency (TEA) to coordinate efforts across various agencies and divisions, ensuring effective implementation of safety policies and best practices. This position was to report directly to the Commissioner and have a direct line to the Governor’s Office, enhancing communication and collaboration without duplicating existing work. Abbott underscored
303-487: A DNA sequence within a chromosome is known as a locus . If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and
404-570: A GC-biased E. coli mutator strain in 1967, along with the proposal of the neutral theory , established the plausibility of mutational explanations for molecular patterns, which are now common in the molecular evolution literature. For instance, mutation biases are frequently invoked in models of codon usage. Such models also include effects of selection, following the mutation-selection-drift model, which allows both for mutation biases and differential selection based on effects on translation. Hypotheses of mutation bias have played an important role in
505-514: A chromosome becoming duplicated (usually by genetic recombination ), which can introduce extra copies of a gene into a genome. Extra copies of genes are a major source of the raw material needed for new genes to evolve. This is important because most new genes evolve within gene families from pre-existing genes that share common ancestors. For example, the human eye uses four genes to make structures that sense light: three for colour vision and one for night vision ; all four are descended from
606-503: A direct line to the Governor’s Office. He will coordinate safety efforts among multiple state agencies and school districts. Governor Abbott has also outlined significant actions to support the Uvalde community and enhance school safety statewide, including financial investments, mental health services, and legislative initiatives. The mission of the Office of School Safety and Security is to build
707-451: A federal investigation. State education officials set an arbitrary limit of 8.5% for the number of students who could receive special education services. By strictly enforcing district compliance with the benchmark, the rate of students receiving special education in Texas fell to 8.5% in 2015, far below the national average of 13%. School districts implemented a wide range of practices to reduce
808-524: A former education board chairman who was the leader of the conservative bloc. Ratliff said in 2013 that the board is "far different" in political complexion that it was in 2010. In 2022, the GOP captured an additional seat, bringing their total to 10 of the 15-member board. Many are social conservatives, campaigning against critical race theory and gender identity lessons. [1] To serve the large number of individual school districts and charter schools in Texas, TEA
909-506: A four day week in polling that was conducted. As of 2011, the school district was rated " academically acceptable " by the Texas Education Agency , which was the same level they had been at since the ratings began in 2004. Forty-nine percent of districts in Texas in 2011 received the same rating. The district has five current schools: While the schools were still segregated, Black students attended Blackshear High School, which
1010-401: A letter dated June 9, 2022, to Commissioner Morath, Governor Abbott emphasized the urgent need to prevent future tragedies like the one in Uvalde by enhancing school safety measures. Despite the comprehensive school safety and mental health legislation passed in 2019 and subsequent efforts, he stated that further actions were necessary before the next school year. Abbott called for the creation of
1111-402: A manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, each long strand of DNA is called a chromosome . The specific location of
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#17330929990081212-405: A nutrient in a long-term laboratory experiment , Flavobacterium evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing, and the soil bacterium Sphingobium evolving an entirely new metabolic pathway that degrades the synthetic pesticide pentachlorophenol . An interesting but still controversial idea is that some adaptations might increase
1313-611: A phenomenon termed de novo gene birth . The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions ( exon shuffling ). When new genes are assembled from shuffling pre-existing parts, domains act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions. For example, polyketide synthases are large enzymes that make antibiotics ; they contain up to 100 independent domains that each catalyse one step in
1414-535: A population are therefore more likely to be replaced by the offspring of parents with favourable characteristics for that environment. In the early 20th century, competing ideas of evolution were refuted and evolution was combined with Mendelian inheritance and population genetics to give rise to modern evolutionary theory. In this synthesis the basis for heredity is in DNA molecules that pass information from generation to generation. The processes that change DNA in
1515-575: A population include natural selection, genetic drift, mutation , and gene flow . All life on Earth—including humanity —shares a last universal common ancestor (LUCA), which lived approximately 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite to microbial mat fossils to fossilised multicellular organisms . Existing patterns of biodiversity have been shaped by repeated formations of new species ( speciation ), changes within species ( anagenesis ), and loss of species ( extinction ) throughout
1616-430: A population is not critical, but instead a measure known as the effective population size. The effective population is usually smaller than the total population since it takes into account factors such as the level of inbreeding and the stage of the lifecycle in which the population is the smallest. The effective population size may not be the same for every gene in the same population. It is usually difficult to measure
1717-439: A population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation . The scientific theory of evolution by natural selection was conceived independently by two British naturalists, Charles Darwin and Alfred Russel Wallace , in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory
1818-433: A population through neutral transitions due to the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities . The time it takes a neutral allele to become fixed by genetic drift depends on population size; fixation is more rapid in smaller populations. The number of individuals in
1919-499: A range of genes from bacteria, fungi and plants. Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains . Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria . It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea . Some heritable changes cannot be explained by changes to
2020-430: A reduction in scope when it was discovered that (1) GC-biased gene conversion makes an important contribution to composition in diploid organisms such as mammals and (2) bacterial genomes frequently have AT-biased mutation. Contemporary thinking about the role of mutation biases reflects a different theory from that of Haldane and Fisher. More recent work showed that the original "pressures" theory assumes that evolution
2121-452: A single ancestral gene. New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function. Other types of mutations can even generate entirely new genes from previously noncoding DNA,
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#17330929990082222-419: A single chromosome compared to expectations , which is called their linkage disequilibrium . A set of alleles that is usually inherited in a group is called a haplotype . This can be important when one allele in a particular haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in the haplotype to become more common in the population; this effect
2323-420: A species or population, in particular shifts in allele frequency and adaptation. Macroevolution is the outcome of long periods of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one—the difference is simply the time involved. However, in macroevolution, the traits of the entire species may be important. For instance, a large amount of variation among individuals allows
2424-544: A species to rapidly adapt to new habitats , lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution might involve selection at different levels—with microevolution acting on genes and organisms, versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of speciation and extinction. A common misconception
2525-411: A striking example are people with the inherited trait of albinism , who do not tan at all and are very sensitive to sunburn . Heritable characteristics are passed from one generation to the next via DNA , a molecule that encodes genetic information. DNA is a long biopolymer composed of four types of bases. The sequence of bases along a particular DNA molecule specifies the genetic information, in
2626-472: A system in which organisms interact with every other element, physical as well as biological , in their local environment. Eugene Odum , a founder of ecology, defined an ecosystem as: "Any unit that includes all of the organisms...in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and nonliving parts) within
2727-428: A trait works in some cases, most traits are influenced by multiple genes in a quantitative or epistatic manner. Evolution can occur if there is genetic variation within a population. Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations ( gene flow ). Despite the constant introduction of new variation through mutation and gene flow, most of
2828-454: Is directional selection , which is a shift in the average value of a trait over time—for example, organisms slowly getting taller. Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilising selection there
2929-442: Is more noticeable . Indeed, the evolution of microorganisms is particularly important to evolutionary research since their rapid reproduction allows the study of experimental evolution and the observation of evolution and adaptation in real time. Adaptation is the process that makes organisms better suited to their habitat. Also, the term adaptation may refer to a trait that is important for an organism's survival. For example,
3030-634: Is Mike Morath. A former member of the Dallas Independent School District's board of trustees, he was appointed commissioner of education by Texas Gov. Greg Abbott on December 14, 2015. The commissioner's role is to lead and manage the Texas Education Agency. The commissioner also co-ordinates efforts between state and federal agencies. TEA is overseen by a 15-member State Board of Education (SBOE) elected from single-member districts. There are no term limits . Terms are four years in length, with one two-year term each decade. Similar to
3131-427: Is a byproduct of this process that may sometimes be adaptively beneficial. Gene flow is the exchange of genes between populations and between species. It can therefore be a source of variation that is new to a population or to a species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or
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3232-434: Is a separate entity not under TEA oversight. In addition to primary and secondary education, TEA has oversight duties with respect to driver's education courses (initial permits) and defensive driving courses (used to have a ticket dismissed and/or for lower insurance premiums). On November 7, 2007, Christine Comer resigned as the director of the science curriculum after more than nine years. Comer said that her resignation
3333-417: Is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype . The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype . Some of these traits come from
3434-464: Is based on standing variation: when evolution depends on events of mutation that introduce new alleles, mutational and developmental biases in the introduction of variation (arrival biases) can impose biases on evolution without requiring neutral evolution or high mutation rates. Several studies report that the mutations implicated in adaptation reflect common mutation biases though others dispute this interpretation. Recombination allows alleles on
3535-407: Is called deep homology . During evolution, some structures may lose their original function and become vestigial structures. Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include pseudogenes , the non-functional remains of eyes in blind cave-dwelling fish, wings in flightless birds,
3636-692: Is called genetic hitchhiking or genetic draft. Genetic draft caused by the fact that some neutral genes are genetically linked to others that are under selection can be partially captured by an appropriate effective population size. A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates. Traits that evolved through sexual selection are particularly prominent among males of several animal species. Although sexually favoured, traits such as cumbersome antlers, mating calls, large body size and bright colours often attract predation, which compromises
3737-431: Is divided in the monitoring and technical assistance division and the school readiness division. Evolution Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within
3838-800: Is divided into 20 regions, each containing an Education Service Center (ESC, sometimes called regional service center or regional education service center). Under Chapter 8 of the Texas Education Code, ESCs perform the following tasks on behalf of TEA: The assistance applies to both districts and schools, including charter schools. Notably, the ESCs have no regulatory authority over districts or schools (TEA headquarters reserves this right to itself). ESCs are not political units, and as such have no taxing authority. They are funded by state and federal funding, as well as by contracts made with individual districts and schools. TEA rates schools and districts using
3939-594: Is measured by an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, fitness is not the same as the total number of offspring: instead fitness is indicated by the proportion of subsequent generations that carry an organism's genes. For example, if an organism could survive well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little genetic contribution to future generations and would thus have low fitness. If an allele increases fitness more than
4040-421: Is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity. This would, for example, cause organisms to eventually have a similar height. Natural selection most generally makes nature the measure against which individuals and individual traits, are more or less likely to survive. "Nature" in this sense refers to an ecosystem , that is,
4141-429: Is that evolution has goals, long-term plans, or an innate tendency for "progress", as expressed in beliefs such as orthogenesis and evolutionism; realistically, however, evolution has no long-term goal and does not necessarily produce greater complexity. Although complex species have evolved, they occur as a side effect of the overall number of organisms increasing, and simple forms of life still remain more common in
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4242-447: Is the nearly neutral theory , according to which a mutation that would be effectively neutral in a small population is not necessarily neutral in a large population. Other theories propose that genetic drift is dwarfed by other stochastic forces in evolution, such as genetic hitchhiking, also known as genetic draft. Another concept is constructive neutral evolution (CNE), which explains that complex systems can emerge and spread into
4343-679: Is the branch of the government of Texas responsible for public education in Texas in the United States. The agency is headquartered in the William B. Travis State Office Building in downtown Austin . Mike Morath , formerly a member of the Dallas Independent School District 's board of trustees, was appointed commissioner of education by Texas Gov. Greg Abbott on December 14, 2015, and began serving on January 4, 2016. Prior to
4444-495: Is the more common means of reproduction among eukaryotes and multicellular organisms. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment. Another hypothesis is that sexual reproduction is primarily an adaptation for promoting accurate recombinational repair of damage in germline DNA, and that increased diversity
4545-439: Is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles: More offspring are produced than can possibly survive, and these conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors are more likely to pass on their traits to
4646-433: Is to instill a culture of constant vigilance and accountability across all Texas schools. A statutory addition from HB3 charged the agency with establishing the Office of School Safety and Security - a division consisting of individuals with substantial expertise and experience in school or law enforcement safety and security operations. The passage of this bill created Texas Education Code, Section. 37.1083 and 37.1084. In
4747-425: The neutral theory of molecular evolution most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. In this model, most genetic changes in a population are thus the result of constant mutation pressure and genetic drift. This form of the neutral theory has been debated since it does not seem to fit some genetic variation seen in nature. A better-supported version of this model
4848-454: The product of a gene , or prevent the gene from functioning, or have no effect. About half of the mutations in the coding regions of protein-coding genes are deleterious — the other half are neutral. A small percentage of the total mutations in this region confer a fitness benefit. Some of the mutations in other parts of the genome are deleterious but the vast majority are neutral. A few are beneficial. Mutations can involve large sections of
4949-519: The ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability). Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to
5050-402: The adaptation of horses' teeth to the grinding of grass. By using the term adaptation for the evolutionary process and adaptive trait for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection. The following definitions are due to Theodosius Dobzhansky: Adaptation may cause either the gain of a new feature, or
5151-507: The alleles are subject to sampling error . This drift halts when an allele eventually becomes fixed, either by disappearing from the population or by replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that begin with the same genetic structure to drift apart into two divergent populations with different sets of alleles. According to
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#17330929990085252-631: The arrangement of the Texas Senate , SBOE members are divided into two groups based in part on the intervening Census: As such, every two years, about half of the SBOE is on the ballot. The board devises policies and sets academic standards for Texas public schools, and oversees the state Permanent School Fund and selects textbooks to be used in Texas schools. Since 2011, the board can still recommend textbooks, but public school districts can order their own books and materials even if their selections are not on
5353-441: The biosphere. For example, the overwhelming majority of species are microscopic prokaryotes , which form about half the world's biomass despite their small size and constitute the vast majority of Earth's biodiversity. Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it
5454-449: The capacity of the regional education service centers (ESCs) and local education agencies (LEAs) to promote the physical and psychological well-being of students and staff - recognizing that safer schools positively impact student outcomes. We align school safety and security expertise with guidance provided through technical assistance to ensure effective best practices are implemented across the state. The Office of School Safety and Security
5555-488: The change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation —when it either disappears from the population or replaces the ancestral allele entirely. Mutations are changes in the DNA sequence of a cell's genome and are the ultimate source of genetic variation in all organisms. When mutations occur, they may alter
5656-549: The citizens, then we ought to take) a thorough look at what they are doing." In 2010, Al Jezeera stated that it was "drafting its own version of American history", including altering school textbooks to remove what it said was a "left-leaning bias" and making changes that are said to have "religious and racial overtones". A series of reports in 2016 by the Houston Chronicle found that since at least 2004, TEA denied special education services to thousands of students, prompting
5757-566: The collective responsibility to provide a safe environment for all students, educators, and staff. Governor Greg Abbott announced the appointment of John P. Scott as the new Chief of School Safety and Security within the Texas Education Agency (TEA) on October 3. This position was created following the tragedy at Robb Elementary School in Uvalde to ensure the implementation of school safety policies and best practices across Texas. Scott, who has an extensive background in security and intelligence, will report directly to Commissioner Mike Morath and have
5858-463: The curriculum controversy, was released. In late January 2013, PBS's Independent Lens aired an abridged version the film. Texas House Speaker Joe Straus of San Antonio, Texas said that the government should "take a look" at the structure of the board and consider a nonpartisan or appointed board if the elected members are "not getting their job done and they're not pleasing the Legislature or
5959-403: The descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as arthropod , squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this
6060-400: The development of thinking about the evolution of genome composition, including isochores. Different insertion vs. deletion biases in different taxa can lead to the evolution of different genome sizes. The hypothesis of Lynch regarding genome size relies on mutational biases toward increase or decrease in genome size. However, mutational hypotheses for the evolution of composition suffered
6161-490: The direct control of genes include the inheritance of cultural traits and symbiogenesis . From a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, for example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, and mutation bias. Evolution by natural selection
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#17330929990086262-489: The evolutionary history of life on Earth. Morphological and biochemical traits tend to be more similar among species that share a more recent common ancestor , which historically was used to reconstruct phylogenetic trees , although direct comparison of genetic sequences is a more common method today. Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from
6363-414: The field or laboratory and on data generated by the methods of mathematical and theoretical biology . Their discoveries have influenced not just the development of biology but also other fields including agriculture, medicine, and computer science . Evolution in organisms occurs through changes in heritable characteristics—the inherited characteristics of an organism. In humans, for example, eye colour
6464-427: The fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. However, even if the direction of selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form. However, a re-activation of dormant genes, as long as they have not been eliminated from
6565-496: The form of requiring the district to submit corrective action plans and regular status reports, assigning monitors to oversee operations (including the authority to assign a management board, which essentially replaces and performs the duties of the elected school board), and in extreme cases closure of a school campus or even the entire school district. The University Interscholastic League (UIL), which oversees academic and athletic interscholastic competition in Texas public schools,
6666-472: The genome and were only suppressed perhaps for hundreds of generations, can lead to the re-occurrence of traits thought to be lost like hindlegs in dolphins, teeth in chickens, wings in wingless stick insects, tails and additional nipples in humans etc. "Throwbacks" such as these are known as atavisms . Natural selection within a population for a trait that can vary across a range of values, such as height, can be categorised into three different types. The first
6767-479: The genome of a species is very similar among all individuals of that species. However, discoveries in the field of evolutionary developmental biology have demonstrated that even relatively small differences in genotype can lead to dramatic differences in phenotype both within and between species. An individual organism's phenotype results from both its genotype and the influence of the environment it has lived in. The modern evolutionary synthesis defines evolution as
6868-640: The idea of developmental bias . Haldane and Fisher argued that, because mutation is a weak pressure easily overcome by selection, tendencies of mutation would be ineffectual except under conditions of neutral evolution or extraordinarily high mutation rates. This opposing-pressures argument was long used to dismiss the possibility of internal tendencies in evolution, until the molecular era prompted renewed interest in neutral evolution. Noboru Sueoka and Ernst Freese proposed that systematic biases in mutation might be responsible for systematic differences in genomic GC composition between species. The identification of
6969-450: The interaction of its genotype with the environment while others are neutral. Some observable characteristics are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. The phenotype is the ability of the skin to tan when exposed to sunlight. However, some people tan more easily than others, due to differences in genotypic variation;
7070-436: The late 1940s, many school districts in Texas did not operate schools but spent money to send children to schools operated by other districts. In the late 1940s, state lawmakers passed a bill abolishing those districts, prompting a wave of mass school district consolidation. TEA is responsible for the oversight of public primary and secondary education in the state of Texas, involving over 1,000 individual school districts in
7171-512: The level of the individual organism are genes called transposons , which can replicate and spread throughout a genome. Selection at a level above the individual, such as group selection , may allow the evolution of cooperation. Genetic drift is the random fluctuation of allele frequencies within a population from one generation to the next. When selective forces are absent or relatively weak, allele frequencies are equally likely to drift upward or downward in each successive generation because
7272-452: The longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed. These outcomes of evolution are distinguished based on time scale as macroevolution versus microevolution. Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction, whereas microevolution refers to smaller evolutionary changes within
7373-405: The loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell. Other striking examples are the bacteria Escherichia coli evolving the ability to use citric acid as
7474-458: The mechanics in developmental plasticity and canalisation . Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Other examples of heritability in evolution that are not under
7575-408: The movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses. Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer . Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. In medicine, this contributes to
7676-720: The need to enhance and expand school safety measures in Texas following the Robb Elementary School tragedy. It highlights the efforts and trainings by the Texas School Safety Center (TxSSC) and outlines specific actions for school districts to improve safety and security. These actions include reviewing and updating Emergency Operations Plans, training staff, conducting safety assessments, and ensuring compliance with state laws. The letter also mandates random inspections to test security measures and calls for legislative support to secure necessary resources. The overall goal
7777-427: The next generation than those with traits that do not confer an advantage. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are seemingly fitted for the functional roles they perform. Consequences of selection include nonrandom mating and genetic hitchhiking . The central concept of natural selection is the evolutionary fitness of an organism. Fitness
7878-451: The number of students, including cutting services for certain children with autism and dyslexia, refusing to conduct eligibility evaluations in other languages, and refusing to accept medical records from other countries. Students who are English Language Learners (ELL) also faced a disproportionate impact resulting in a 20% difference in the rate of ELL students getting special education services compared to native speakers. In Houston ISD ,
7979-499: The offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombination , sexual organisms exchange DNA between two matching chromosomes. Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles. Sex usually increases genetic variation and may increase
8080-456: The other alleles of that gene, then with each generation this allele has a higher probability of becoming common within the population. These traits are said to be "selected for ." Examples of traits that can increase fitness are enhanced survival and increased fecundity . Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele likely becoming rarer—they are "selected against ." Importantly,
8181-578: The overall process, like a step in an assembly line. One example of mutation is wild boar piglets. They are camouflage coloured and show a characteristic pattern of dark and light longitudinal stripes. However, mutations in the melanocortin 1 receptor ( MC1R ) disrupt the pattern. The majority of pig breeds carry MC1R mutations disrupting wild-type colour and different mutations causing dominant black colouring. In asexual organisms, genes are inherited together, or linked , as they cannot mix with genes of other organisms during reproduction. In contrast,
8282-579: The overhaul of its special education practices. Advocates raised concerns about the lack of a competitive bidding process and the Georgia-based company's qualifications, and a former TEA special education director filed a federal complaint about TEA violating state procurement processes. In 2018, the U.S. Department of Education found that "Texas violated federal law by failing to ensure students with disabilities were properly evaluated and provided with an adequate public education." A multi-year strategic plan
8383-527: The presence of hip bones in whales and snakes, and sexual traits in organisms that reproduce via asexual reproduction. Examples of vestigial structures in humans include wisdom teeth , the coccyx , the vermiform appendix , and other behavioural vestiges such as goose bumps and primitive reflexes . However, many traits that appear to be simple adaptations are in fact exaptations : structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in
8484-464: The process. One example is the African lizard Holaspis guentheri , which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation. Within cells, molecular machines such as the bacterial flagella and protein sorting machinery evolved by
8585-601: The ranking system. The Texas Education Agency is funded by the people of the State of Texas , at the direction of their elected legislature and with the consent of the Governor of Texas . The agency's budget must be approved on the legislature's biannual schedule. Revenues for the agency come from the state general fund (primarily sales taxes), the federal government, the Permanent School Fund (a sovereign wealth fund created by
8686-494: The rate of evolution. The two-fold cost of sex was first described by John Maynard Smith . The first cost is that in sexually dimorphic species only one of the two sexes can bear young. This cost does not apply to hermaphroditic species, like most plants and many invertebrates . The second cost is that any individual who reproduces sexually can only pass on 50% of its genes to any individual offspring, with even less passed on as each new generation passes. Yet sexual reproduction
8787-408: The relative importance of selection and neutral processes, including drift. The comparative importance of adaptive and non-adaptive forces in driving evolutionary change is an area of current research . Mutation bias is usually conceived as a difference in expected rates for two different kinds of mutation, e.g., transition-transversion bias, GC-AT bias, deletion-insertion bias. This is related to
8888-582: The same four criteria. According to the TEA, the number of state schools and districts receiving the top ratings of "exemplary" and "recognized" increased from 2,213 in 2005 to 3,380 in 2006. In 2020, all schools were given a "not rated" designator due to the COVID-19 pandemic . In addition to the state ranking, districts and schools can be awarded additional commendations (referred to as Gold Performance acknowledgements) for other noteworthy accomplishments not included in
8989-417: The same strand of DNA to become separated. However, the rate of recombination is low (approximately two events per chromosome per generation). As a result, genes close together on a chromosome may not always be shuffled away from each other and genes that are close together tend to be inherited together, a phenomenon known as linkage . This tendency is measured by finding how often two alleles occur together on
9090-552: The sequence of nucleotides in the DNA. These phenomena are classed as epigenetic inheritance systems. DNA methylation marking chromatin , self-sustaining metabolic loops, gene silencing by RNA interference and the three-dimensional conformation of proteins (such as prions ) are areas where epigenetic inheritance systems have been discovered at the organismic level. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of
9191-406: The spread of antibiotic resistance , as when one bacteria acquires resistance genes it can rapidly transfer them to other species. Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean weevil Callosobruchus chinensis has occurred. An example of larger-scale transfers are the eukaryotic bdelloid rotifers , which have received
9292-532: The state and charter schools . It is also responsible for the safety of students. However, it does not have any jurisdiction over private or parochial schools (whether or not accredited ) nor over home schools . Although school districts are independent governmental entities, TEA has the authority to oversee a district's operations (either involving an individual school or the entire district) if serious issues arise (such as poor standardized test performance, financial distress, or mismanagement). This can be in
9393-408: The state with revenues from public lands), and other sources. * Budget figure is projection; all other years are actual expenditure as reported by TEA After the Uvalde school shooting, Governor Greg Abbott instructed state school safety and education officials to conduct random assessments on access control in Texas public and charter schools. In a letter dated June 1, 2022, Gov. Abbott emphasized
9494-411: The state's largest school district, after the 8.5% goal was met the standard was lowered to 8%. As a result, the district cut hundreds of special education positions, postponed diagnostic evaluations to second grade, and created a list of disqualifying factors that keep students from getting services. TEA issued a no-bid contract for $ 4.4 million to SPEDx in 2017 to analyze student records to assist with
9595-448: The state-approved list. So far, most districts have continued to follow the state-endorsed textbooks, but that trend is expected to change in the next two years as the districts become more cognizant of their available options. Thomas Ratliff, a moderate Republican and the son of former Lieutenant Governor Bill Ratliff of Mount Pleasant , in 2010 unseated the Bryan dentist Don McLeroy ,
9696-640: The survival of individual males. This survival disadvantage is balanced by higher reproductive success in males that show these hard-to-fake , sexually selected traits. Evolution influences every aspect of the form and behaviour of organisms. Most prominent are the specific behavioural and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by cooperating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis . In
9797-642: The system...." Each population within an ecosystem occupies a distinct niche , or position, with distinct relationships to other parts of the system. These relationships involve the life history of the organism, its position in the food chain and its geographic range. This broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural selection. Natural selection can act at different levels of organisation , such as genes, cells, individual organisms, groups of organisms and species. Selection can act at multiple levels simultaneously. An example of selection occurring below
9898-487: Was a result of pressure from officials who claimed that she had given the appearance of criticizing the teaching of intelligent design . In 2009, the board received criticism from more than 50 scientific organizations over an attempt to weaken science standards on evolution . In October 2012, The Revisionaries , a documentary film about the re-election of the chairman of the Texas Board of Education Don McLeroy and
9999-473: Was accredited in 1924. The school was subsequently renamed in honor of R.C. Fisher, who died suddenly at 44. The school closed in 1966. In August 2021, the district broke ground on a memorial to honor the students who attended Athens schools during the era of segregation. Bridges Center, which offered alternative instruction to high school students, closed in 2015. Texas Education Agency accountability ratings system The Texas Education Agency ( TEA )
10100-655: Was first set out in detail in Darwin's book On the Origin of Species . Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) traits vary among individuals with respect to their morphology , physiology , and behaviour; (3) different traits confer different rates of survival and reproduction (differential fitness ); and (4) traits can be passed from generation to generation ( heritability of fitness). In successive generations, members of
10201-410: Was released in 2018. In a grant application to the agency, TEA stated that they will not be able to ensure adequate services for special education students until June 2020. In September 2020, in the midst of several attempts to place Houston ISD under state control, TEA investigators recommended a state-appointed conservator be selected to oversee the district. The current commissioner of education
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