Biology 42
Conjugation in Bacteria
Definition : The unidirectional transfer of DNA from our cell to another through the cytoplasmic bridge is called Conjugation. Introduction : Conjugation was discovered by J. Lederbery and E.L. Tautum in e. Coli During conjugation DNA is transferred from a donor cell to a recipient cell through specialized conjugation tube ( an intercellular connection), […]
Neo – Darwinism (Theory of Evolution)
Neo – Darwinism Definition : Neo-Darwinism is a modified version of Darwin’s theory, that regards evolution as a change in gene frequencies due to mutation, natural selection considered as the most important, although not the only cause for such changes. Or, Definition : Neo – Darwinism is a modified version of Darwin’s theory which takes […]
Recapitulation theory of Haeckel
Recapitulation theory of Haeckel Definition : The theory says Embryonic stages of higher animals resemble the adults of ancestors. Thus, during embryonic development, an organism presents successive stages of its ancestors. Introduction : Ernst Heckel (1811) stated “Ontogeny recapitulates Phylogeny” i.e development of an individual repeats the evolutionary history of the race Generalised features like […]
Mutation Theory of Evolution
Mutation Theory of Evolution Definition : According to this theory, evolution is a discontinuous and jerky process, where new species arise from preexisting species in a single generation. Introduction : Hugo De Vries (Dutch botanist0 suggested the mechanism for variations in species as Mutation Theory. He worked on the plant, evening primrose – O. […]
Derwinism (Theory of Natural Selection)
Derwinism (Theory of Natural Selection) Definition : Darwinism explains the mechanism of evolutionary changes by natural selection by Darwin. Introduction : Darwin’s theory of Natural selection published in 1859 – “ The origin of Species by Natural Selection”. This theory explains the origin of species by means of natural selection and preservation of favorable races in […]
Neo-Lamarkism (Theory of Evolution)
Neo – Lamarkism (Theory of Evolution) Definition : Modified Lamarkism which states that environment induces variation and only germinal variations are inheritable. Introduction : Lamarkism proved to be unsatisfactory in explaining evolution. But then, long forgotten Lamrkism was enlightened with the new knowledge of genetics, giving rise to Neo-Lamarkism. Neo – Lamarkism confirmed that environment plays a […]
Lamarkism (Theory of Evolution)
Lamarkism Theory of Evolution Definition : Theory of inheritance of acquired characters by ham ark can be defined as the variations/changes, developed in an organism (from normal characters) may be due to change in its surrounding environment or in the functioning (use or discuss) of organs, in its lifetime, to fulfill its new needs. Or As the […]
Stanley – Miller Experiment
Definition : (1953) Standey Miller Experimentally proved the formation of simple organic compounds from simpler molecules under reducing conditions. Introduction : The oparin – Holdone hypothesis was effectively proved in the laboratory by Stanley Miller, a student working in the laboratory of Harold Orey. Miller build an apparatus that simulated (i.e. created an artificial primitive […]
Chemical Evolution (Chemogeny)
Definition : The theory of chemical evolution postulates that “Life occurs as a natural result of the evolution of inorganic matter”. Introduction : In 1920’s Oparin and Haldane, developed a hypothesis on the chemical origin of life. They proposed that the primitive atmosphere of earth contained primarily reduced substances like methane, ammonia, and water instead of […]
Formation of Earth – BIG BANG THEORY
Introduction : Big Bang Theory is today’s dominant scientific theory about the origin of the universe. According to this theory. “Universe was created about 18 billion years ago from the random, cosmic explosion of a subatomic ball that hurled (spread) matter and energy in all direction. This newly created matter and energy coagulated into stars, […]
Evolution
Definition : Evolution means Change in time in biology, this means, “Change in biological entities in time” Introduction : Evolution is the process of continuous changes and involves the trends like increased adaptations, the complexity of structures and functional efficiency. Evolution involves the changes, in flora and fauna that have occurred once millions of years […]
Genetic Disorder
Genetic Disorders (1) Autosomal Genetic Disorder : Down’s syndrome or Mongolesm Cri-du-chat syndrome (2) Sex chromosome – linked genetic disorder Turner’s syndrome Klinefelter’s syndrome Definition : Any disorder which results due to chromosomal aberration: addition or deletion of chromosome referred as genetic disorder. Introduction : Genetic disorder which results due to chromosomal aberration […]
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