What is the foil method in biology


evolution, general development, transformation, further development. In the biology E. refers to all processes that have reshaped life on earth from its earliest forms to the great diversity found today. The process of E. is neither directly observable nor demonstrable experimentally, but many results from various biological directions can be explained and supported by a theory of E. Typical examples of such findings include homologies that suggest a relationship between two or more groups; i.e. a trait is homologous if it can be traced back to the trait of a common parent species. In this sense, the term homology is also applied to non-morphological characteristics (physiological, molecular, ethological). The occurrence of rudiments and atavisms (atavism) also support the theory of an E. of living beings. Paleontological findings in this context include fossils, for example as main group representatives or as intermediate forms (such as Archeopteryx or Ichtyostega). There are biogeographical distribution phenomena that can be easily explained by theories of allopatric speciation (allopatry) and adaptive radiation and thus by E. Likewise, correspondences during embryonic development serve as evidence of phylogenetic relationships, a fact that was already formulated by E. Haeckel in his basic biogenetic rule.

Evolution factors are, as it were, the engine of the E .; this includes all factors that change the gene frequencies in a population. The most important evolutionary factors are mutation and recombination of DNA in the course of meiosis. In addition, the genetic drift, i.e. the change in gene frequencies through the random selection of genotypes, the gene flow through the immigration and emigration of individuals and the Meiotic drive, the accumulation of certain genotypes due to uneven gamete production, contributes to genetic variability. While the aforementioned factors increase genetic variability, selection leads to selection from the available material; The transmission rate of genes, i.e. the contribution that an individual makes to the gene stock of the next generation and thus the probability with which it will leave genes in the progeny in the long term, is called (Darwinian or, in the case of reproductive support, relatives as Hamiltonian ) fitness designated. Selection steers the evolutionary processes in the direction of the optimal adaptation in each case.

The origin of life. Investigations by planetologists have shown that the earth was habitable at least four billion years ago. On the other hand, paleontologists have already discovered traces of life in rocks that are 3.9 billion years old, so that earthly life only had around 100 million years to develop. The question of the origin of life is the question of the origin of prokaryotes. Most biological researchers favor the thesis that life evolved from inanimate matter, which initially formed molecular aggregates that were possibly capable of replication and metabolism. This process is called chemical E.. and divided into four hypothetical stages: 1) Abiotic synthesis and accumulation of small organic molecules, including amino acids and nucleotides. 2) Their linkage to polymeric macromolecules (including proteins and nucleic acids). 3) The aggregation of abiotic connections to spherical structures (Protobionts) with specific chemical properties. 4) The development of an inheritance mechanism.

The basic possibilities of chemical E. are tested again and again in laboratory experiments. The most famous attempt is probably that Urey Miller experiment, in which a primordial atmosphere of water vapor, hydrogen, methane and ammonia was exposed to electrical discharges and the resulting reaction products were collected in an aqueous solution. Among other things, all 20 proteinogenic amino acids as well as various sugars, lipids, purine and pyrimidine bases and (in the presence of phosphate) also ATP were formed, which could have accumulated on the primordial earth in the oceans in a kind of "primordial soup". The polymerization reactions could have been promoted by the binding of the substrates to clay minerals, whereby metal atoms such as iron and zinc could have acted as catalysts. A role similar to that of clay minerals could also have been played by pyrite, a combination of iron and sulfur, such as that which occurs in the vicinity of so-called "black smokers" on the deep sea floor. In appropriate experiments, the formation of amino acids and their polymerization into polypeptides could be simulated, which has led, among other things, to the hypothesis that life could also have originated on the sea floor under comparable conditions. This theory was supported at the time by the discovery of the first archaebacteria by C. Woese in the vicinity of "black smokers".

Another prerequisite for the development of living organisms is the existence of concentration gradients. These are ensured by the formation of reaction spaces, such as those caused by the formation of microspheres through proteinoids or micelles through fatty acids. Since cosmic dust particles contain nitriles, which react with water to form fatty acids, they offer a good basis for the creation of such reaction spaces. This hypothesis, which postulates that cosmic dust at least played an important role in the origin of life on earth, is also supported by the fact that the self-organization necessary for the creation of living organisms, which can only take place in very specific spatial structures and in specific chronological sequence can take place, in such dust particles very good conditions prevailed. In addition, it has been shown that, in addition to lipids, proteins and nucleic acids can also be formed in them after contact with water. Silicate and sulfidic mineral grains served as reaction-promoting substrates, metals such as iron, nickel and zinc could, as in the previously mentioned hypothesis, take on the role of catalysts; however, the latter could also have been taken over by the nucleic acids formed (for RNA it is assumed that it was formed first) (ribozymes). However, there is also the hypothesis that at least simple self-replication of the RNA in conjunction with polypeptides that may have exhibited enzymatic activity could have led to the development of the first steps of replication and translation of genetic information without an enveloping membrane being present.

If a protobiont had arisen as a hypothetical precursor of the cell in one of the ways described (or through a combination of the same), which would have been capable of self-replication and division (according to I. Prigogine, growing systems become unstable from a certain size and spontaneously disintegrate into two similar smaller ones) , so his offspring would vary, since there would always be mutations in the form of "copying errors". With the model of the hypercycle, M. Eigen has described how replicative systems can arise through cyclic reaction sequences between prebiotic nucleic acids and proteins. At this point the chemical E. goes into a biological E.. about, which takes place in the Darwinian sense through different reproductive successes of differing individuals of a population.