Evolution
- Lafyva
- May 24, 2020
- 8 min read
Updated: Sep 6
But I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of con- ception. Several reasons make me believe in this; but the chief one is the remarkable effect which confine- ment or cultivation has on the functions of the repro- ductive 8)’stem ; this system appearing to be far more susceptible than any other part of the organisation, to the action of any change in the conditions of life.
On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life(first edition)
Publication date1859
The 1909 book titled The Foundations of The Origin of Species
This edition is distinct from the original 1859 work but is significant for understanding the evolution of Darwin's thought.
"Some authors believe it to be as much the function of the reproductive system to produce individual differences, or slight deviations of structure, as to make the child like its parents. But the fact of variations and monstrosities occurring much more frequently under domestication than under nature, and the greater variability of species having wide ranges than of those with restricted ranges, lead to the conclusion that variability is generally related to the conditions of life to which each species has been exposed during several successive generations. In the first chapter I at-tempted to show that changed conditions act in two ways, directly on the whole organization or on certain parts alone, and indirectly through the reproductive system. In all cases there are two factors, the nature of the organism, which is much the most important of the two, and the nature of the conditions."
On 22-24 June 1909 over 400 scientists and dignitaries from 167 different countries gathered at Cambridge to celebrate the centenary of Darwin's birth and the fiftieth anniversary of the publication of On the Origin of Species.
AI Overview
Learn more
According to Darwin, the "nature of the organism" and "conditions of life" significantly influence the variations present within a species, particularly impacting the reproductive system, where these variations can be passed on to offspring through natural selection, leading to evolution over time; essentially, the environment an organism lives in shapes which traits are advantageous and thus more likely to be reproduced in future generations.
(C) It may be supposed that the environment in which the organism is placed controls the nature of the mutations which occur in it, and so directs its evolutionary course ; much as the course of a projectile is controlled by the field of force in which it flies.
(D) It may be supposed that the mutations which an organism undergoes are due to an 'inner urge' (not necessarily connected with its mental state) implanted in its primordial ancestors, which thereby directs its predestined evolution.
The two last suggestions give no particular assistance towards the understanding of adaptation, but each contains at least this element of truth; that however profound our ignorance of the causes of mutation may be, we cannot but ascribe them, within the order of Nature as we know it, either to the nature of the organism, or to that of its surrounding environment, or, more generally, to the interaction of the two.
Variation exists within all populations of organisms. This occurs partly because random mutations arise in the genome of an individual organism, and offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits. The environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment. Because individuals with certain variants of the trait tend to survive and reproduce more than individuals with other, less successful variants, the population evolves.
Gene expression and regulation are mediated by DNA sequences, in most instances, directly upstream to the coding sequences by recruiting transcription factors, regulators, and a RNA polymerase in a spatially defined fashion. Few nucleotides within a promoter make contact with the bound proteins. The minimal set of nucleotides that can recruit a protein factor is called a cis-acting element. This article addresses a powerful mutagenesis strategy that can be employed to define cis-acting elements at a molecular level. Technical details including primer design, saturation mutagenesis, construction of promoter libraries, phenotypic analysis, data analysis, and interpretation are discussed.
This yields a very simple statistical test. The boundary regions are approximately one-third of a gene: Do introns lie preferentially in these regions, or are their positions random? Again, we considered ancient conserved regions, choosing ones that correspond to three-dimensional structures homologous to bacterial genes without introns and to eukaryotic sequences with introns, to ask: Do those intron positions in the eukaryotic homologs tend to lie in the boundary regions or do they not? The two theories predict quite opposite effects. These are all derived introns on the introns-late model, they were added to the preexisting gene, and their positions should be random. The early-intron model predicts that these positions should fall in the boundary regions.
Biological Significance Kissing in the Light of Modern Achievements of Genetics
The role of bio communicators in unicellular prokaryotic organisms (for example, bacteria) is played by plasmids. However, they are not able to perform all the functions inherent in bio communicators. Plasmids carry out active horizontal gene transfer in prokaryotes. Analogues of plasmids for eukaryotes are viruses. Bacteriophages (bacterial viruses) are not bio communicators (migratory organelles) of bacterial cells, and this is indicated by the fact that they forcibly introduce their genetic material into the bacterial cell. Thus, bacteriophages are bio communicators of various eukaryotic cells (their migrating organelles), which carry out and ensure the regulation of various biochemical processes in bacterial cells and their numbers (from the side of the owner of this bio communicator). According to the above information about the acquired and main genomes, a new definition of the term “phenotype” can be given. The phenotype is a manifestation of the totality of genes obtained by vertical and horizontal channels of gene transfer and the result of their interaction. Therefore, the phenotype is the expression (manifestation) of the genotype. The body throughout life - from the moment of fertilization of the egg (the formation of the zygote) to death, has the opportunity to enrich its genotype due to an increase in the share of the acquired genome. This is accomplished by horizontal gene transfer. Information received by the sensor systems (receptors) of the body about the external and internal environment actively affects the change (enrichment or depletion) of the acquired genome of the body. As a result, the phenotype changes. However, these changes affect only the genes of certain cells of certain body tissues. For example, cells of the central nervous system of humans or animals, the immune system, or liver cells change. If changes affect the germ cells, then new signs and properties will begin to be inherited, from generation to generation.
The majority of evolutive movements are degenerative. Progressive cases are exceptional. Characters appear suddenly that have no meaning in the atavistic series. Evolution in no way shows a general tendency toward progress… . The only thing that could be accomplished by slow changes would be the accumulation of neutral characteristics without value for survival. Only important and sudden mutations can furnish the material which can be utilized by selection.
J.B.S. Haldane is where the Equalitarian's theory comes from.
In biology, saltation (from Latin saltus 'leap, jump') is a sudden and large mutational change from one generation to the next, potentially causing single-step speciation. This was historically offered as an alternative to Darwinism.
It has been remarked that unlike what is true of the other founders of population genetics, Haldane’s picture of evolution was not underpinned by a single dominant idea. In this respect Haldane was the outlier. https://www.ias.ac.in/article/fulltext/jgen/096/05/0765-0772
24Fifteen years after the completion of the series, in 1949, when the mathematician, J. Neyman began composing a short treatise on probability and statistics, with a chapter devoted to genetics, he asked Haldane for his most important papers (J. Neyman to Haldane, November 14, 1949, Box 19, UCL). Haldane’s response was unequivocal: “I think my most important work is in the Transactions of the Cambridge Philosophical Society from 1924 to 1936” (Haldane to J. Neyman, November 22, 1949, Box 19, UCL). The details of the statement are inaccurate — only Part I of the “Mathematical Theory” had appeared in the Transactions; the next eight appeared in the Proceedings. https://www.sciencedirect.com/science/article/pii/B9780444515438500058
HALDANE AND THE EMERGENCE OF MODERN EVOLUTIONARY THEORY
The Modern Synthesis Evolution and the Organization of Information https://link.springer.com/book/10.1007/978-3-030-86422-4
Evolutionary biology has been a remarkably dynamic area since its foundation. Its true complexity, however, has been concealed in the last 50 years under an assumed opposition between the “Extended Evolutionary Synthesis” and an “Alternative to the Evolutionary Synthesis”. This multidisciplinary book series aims to move beyond the notion that the development of evolutionary biology is structured around a lasting tension between a Darwinian tradition and a non-Darwinian tradition, once dominated by categories like Darwinian Revolution, Eclipse of Darwinism, Evolutionary Synthesis, and Post-Synthetic Developments. 3.3.2.3 From Phase 1 to Phase 2 of the Synthesis As noted, Gould has discussed the transitions toward the Modern Synthesis in terms of restriction and hardening (Gould 2002). The emergence of neo-Darwinism and the development of population genetics, which I have merely outlined above with a traditional focus upon Fisher, Haldane, and Wright, was the period of restriction. The focus of evolutionary theory was drawn away from saltation and orthogenesis by genetic gradualism and the power of natural selection operating over random variation. Evolutionary accounts now had to make sense in genetic terms, but as Gould notes there was a pluralism about the role of selection and genetic drift and other random phenomena. Much of the work following Fisher, Haldane, and Wright was about bringing population genetics into contact with various areas of biology, including Dobzhansky’s efforts to demonstrate genetic variation in nature, Mayr’s work on systematics and also on speciation, and Simpson’s alignment with paleontology (Mayr 1982; Pigliucci 2007). However, in the final phase of the synthesis natural selection was, according to Gould, afforded prime place as the creative force of evolution, and this was linked to the adoption of what he terms adaptationism, where phenotypes must be “analyzed as problems in adaptation” (Gould 2002: 505). Gould (2002) analyzes the hardening in the work of Dobzhansky, Mayr, and Simpson, showing a gradual shift to the primacy of natural selection and adaptationism from the 1940s and through into the 1960s. While some of this was a result of empirical results gathering momentum for natural selection and adaptationist hypotheses he also gives some credence to Smocovitis’ view that this may have been a social response to World War II, such that evolution by natural selection was linked to progress and improvement in a way that random models of drift simply could not be (Smocovitis 1996).6
Ernst Mayr's interactions with J. B. S. Haldane
Early in this century, only a few biologists accepted that natural selection was the chief cause of evolution, until the independent calculations of John Burdon Sanderson Haldane (1892–1964), Sewall Wright and R. A. Fisher demonstrated that ideal populations subject to Mendel's laws could behave as Darwin had said they would. Evolutionary theorist John Maynard Smith, a student of Haldane's, has raised the question of why Haldane, who was no naturalist, took up the subject of evolution, and he suggests that the answer may have to do with Haldane's lively interest in religion. In fact Maynard Smith's answer has much more evidence in its favour than he knew. https://www.cambridge.org/core/journals/british-journal-for-the-history-of-science/article/abs/j-b-s-haldanes-darwinism-in-its-religious-context/6B762D7020D75D17C0A83354E6B7806E
