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Generation in Biological Definition

Abiogenesis

... , in its most general sense, is the hypothetical generation of life from non-living matter. Today, the term ... incorrect. These early concepts of spontaneous generation (referred to here as "Aristotelian abiogenesis" ... abiogenesis , also known as spontaneous generation , (and, in older texts, Generatio aequivoca, ...

Evolution

... frequency of alleles in a population from one generation to the next. Darwin's theory of evolution ... In addition, abiogenesis — the generation of life from non-living matter — has never ... populations, where chance fluctuations from generation ...

Genetic drift

... fitness, on average the number of carriers in one generation is proportional to the number of carriers in the ... But the average is never tallied, because each generation parents the next one only once. Therefore the ... individuals with a rare allele in the originating generation can produce a population that has allele ...

Hardy-Weinberg principle

... states that, under certain conditions, after one generation of random mating , the genotype frequencies at ... for the HWP, is that the alleles for the next generation for any given individual are chosen ... A being dominant, and that in any given generation the number of pure dominants (AA), heterozygotes ...

Mendelian inheritance

... of inheritance that were passed intact from one generation to the next. These units would later come to be ... (white) phenotype look alike in the F 1 (first) generation and show a 3:1 ratio in the F 2 (second) generation Mendel's findings allowed other ...

Punctuated equilibrium

... gradually, with no great changes from one generation to the next. This can be understood by ... short period of time). If the average generation is 7 years, then the given timespan corresponds ... at the minute, gradual rate of only 0.005 cm per generation (= 50 cm / 10000 generations). The theory is ...

Louis Pasteur

... the growth of microorganisms in nutrient broths is not due to spontaneous generation . He exposed boiled broths to air in vessels that contained a filter to ... broth. Thus, Pasteur dealt the death blow to the theory of spontaneous generation and supported germ theory. While Louis Pasteur did not develop germ ...

Memory B cell

... can recognize the pathogen and start to divide. Quickly, they form a new generation of cells, and memory cells. The new generation kills off the pathogen so quickly the body does not become noticeably ...

Parthenogenesis

... but instead hemiclonal , with half the genome passing intact to the next generation while the other half is replaced. In hybridogenetic species, females mate ... offspring got from their own mother. This process continues, so that each generation is half (or hemi-) clonal on the mother's side and half new genetic ...

Alfred Russel Wallace

... at least three times in history: 1. The creation of life from inorganic matter. 2. The introduction of consciousness in the higher animals. 3. The generation of the above-mentioned faculties in mankind. He also believed that the raison d'tre of the universe was the development of the human spirit. (See ...

Antibiotic resistance

... of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics , such as second and third generation cephalosporins , greatly hastens the development of methicillin resistance, even in organisms that have never been exposed to the selective pressure ...

Ecological genetics

... field of population genetics ) studies wild populations of organisms. Studies are often done on insects and other organisms that have short generation times, and thus evolve at fast rates. History Although work on natural populations had been done previously, it is acknowledged that the ...

Epigenetics

... In both cases, the object of study includes how gene regulatory information that is not expressed in DNA sequences is transmitted from one generation (of cells or organisms) to the next - that is (harking back to the Greek prefix), 'in addition to' the genetic information encoded in the DNA. In ...

Evolutionary biology

... evolutionary researchers are taking advantage our extensive understanding of microbial physiology, the ease of microbial genomics , and the quick generation time of some microbes to answer evolutionary questions. Similar features have led to progress in viral evolution, particularly for bacteriophage ...

Experimental evolution

... selection acts upon and what brought about the adaptations and to find out how exactly these mutations work. Because of the large number of generation required for adaptation to occur, evolution experiments are typically carried out with microorganisms such as bacteria or viruses . ...

Heterozygote

... as PP for the dominant homozygote pink flower and pp for the recessive homozygote white flower. When these are crossed, the F1 or second generation will be heterozygote for the colour of the flower and this will be indicated with Pp . All F1 plants will flower pink. Some traits are neither ...

Homeostasis

... occurring systems than negative feedback, but it has its applications. For example, in nerves , a threshold electric potential triggers the generation of a much larger action potential . (See also leverage points .) Ecological homeostasis In the Gaia hypothesis , James Lovelock ...

Jean-Baptiste Lamarck

... that the acquired modifications are common to both sexes, or at least to the individuals which produce the young. Lamarck saw spontaneous generation as being ongoing, with the simple organisms thus created being transmuted over time (by his mechanism) becoming more complex and closer to some ...

Konrad Lorenz

... in the 1970s . Lorenz's most enduring contributions thus seem to be his empirical work, especially on imprinting; his influence on a younger generation of ethologists; and his popular works, which were enormously important in bringing ethology to the attention of the general public and are still ...

Metabolism

... Entner-Doudoroff Pathway , an alternative glycolysis pathway in few bacteria . Pentose phosphate pathway (hexose monophosphate shunt), generation of NADPH from glucose. Protein catabolism , the hydrolysis of proteins into amino acids . Aerobic respiration Electron ...

Metapopulation

... e . Additionally, 1- N of the patches are unoccupied. Each of these may become populated by colonization. Let c be a constant rate of propagule generation for each of the N occupied patches. This give a probability of cN for each unoccupied patch to be colonized. So for each time step, the change ...

Microbiology

... have many traits that make them ideal model organisms : They are small, therefore they do not consume many resources Some have very short generation times (the time needed for division of a bacterial cell in two in optimal conditions; ~30 minutes for E. coli , but 12 to 24 hours for ...

Mitosis

... - that tells the cell to wait before proceeding to anaphase. There are many theories as to how this is accomplished, some of them involving the generation of tension when both microtubules are attached to the kinetochore. When chromosomes are bivalently attached - when both kinetochores are attached ...

Molecular evolution

... Beyond this number of alleles, the selective advantage of presence of those alleles in heterozygous genotypes would be cancelled out by continual generation of less fit homozygous genotypes. These results became important in the formation of the neutral theory, because neutral (or nearly neutral) ...

Modern evolutionary synthesis

... (crossing over of homologous chromosomes during meiosis ). Evolution consists primarily of changes in the frequencies of alleles between one generation and another as a result of genetic drift , gene flow and natural selection . Speciation occurs gradually when populations are reproductively ...

Antibiotic resistance

... of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics , such as second and third generation cephalosporins , greatly hastens the development of methicillin resistance, even in organisms that have never been exposed to the selective pressure ...

Magnetic resonance imaging

... precise nature of the relationship between neural activity and the BOLD signal is a subject of current research. The BOLD effect also allows for the generation of high resolution 3D maps of the venous vasculature within neural tissue. Interventional MRI Because of the lack of harmful effects on the ...

Origin of life

... Research into the origin of life is the modern incarnation of the ancient concept of abiogenesis . Abiogenesis, in its most general sense, is the generation of life from non-living matter. The term is primarily used in the context of biology and the origin of life. Abiogenesis was long considered to be a ...

Population genetics

... and another set of laws that map the resulting population ( P 2 ) back to genotype space ( G 2 ) where Mendelian genetics can predict the next generation of genotypes, thus completing the cycle. Even leaving aside for the moment the non-Mendelian aspects revealed by molecular genetics , this is ...

Red Queen

... the metaphor Red Queen represents the situation in nature where creatures must adapt quickly to changing environmental threats just to survive from generation to generation. In Lewis Carroll 's Through the Looking Glass , from which the metaphor is originally derived, Alice complains that she has to ...

Retrovirus

... Central dogma of molecular biology . Reverse transcriptase activity outside of retroviruses has been found in almost all eukaryotes, enabling the generation and insertion of new copies of retrotransposons into the host genome. Because reverse transcription is missing the usual "proofreading" of DNA ...

Rudolf Steiner

... as something intended to be alive and metamorphic. Nor was Steiner shy about saying that his works would gradually become obsolete, and that each generation should rewrite them. Individual freedom and spiritual independence are among the values Steiner most emphasized in his books and lectures. ...

Species

... regarded as separate species. See also microspecies under apomixis , for species that reproduce without meiosis or mitosis so that each generation is genetically identical to the previous generation. In practice, these definitions often coincide, and the differences between them are more a ...

Mitosis

... - that tells the cell to wait before proceeding to anaphase. There are many theories as to how this is accomplished, some of them involving the generation of tension when both microtubules are attached to the kinetochore. When chromosomes are bivalently attached - when both kinetochores are attached ...

Thylakoid

... , NADPH, or both in photosynthesis. The stacks connect by membranous channels as a single functional compartment. The molecular mechanism of ATP generation in chloroplasts is similar to that in mitochondria . ...

Unsolved problems in biology

... time and under specific conditions? What is the complete function of the regulator genes ? The building block of life may be a precursor to a generation of electronic devices and computers , but what are the electronic properties of DNA? Does Junk DNA function as molecular garbage? ...

Vestibular system

... Using these direct connections, eye movements lag the head movements by less than 10 ms, one of the fastest reflexes in the human body. The automatic generation of eye movements from movements of the head is called vestibulo-ocular reflex , or short VOR . This reflex, combined with the push-pull ...

Virus evolution

... viruses , have fairly high mutation rates (on the order of one point mutation or more per genome per round of replication in RNA viruses) and short generation times. As a consequence, many viruses can adapt to changes in their environment within months. Virus evolution is an important aspect of the ...

Astrobiology

... figures in much science fiction as the fictional science of the biology of alien organisms. This use of the term demonstrates the speculative generation of possible models of such life, e.g. silicon -based. Search for extraterrestrial life As of 2005 , there is no definite evidence of ...
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