Tag: the paths traversed by life

Hugo de vries was born in Haarlem, Netherlands. He was a Professor of Botany, when he began his genetic experiments with plants in 1880. De Vries believed species evolve from other species through sudden, large changes of character traits. De Vries based this 'theory of mutation' on work he did using Oenothera lamarckiana - the evening Primrose. He observed that the original plant would occasionally have offspring with significant phenotypic differences such as leaf shape and plant sizes. Some of the offspring would pass the new 'sport (mutation) to their progeny, these de Vries designated as new species.

According to Hugo de Vres, new species are not formed by continuous variations but by sudden appearance of variations, which he named as mutations. Hugo de Vries stated that mutations are heritable and persist in successive generations. Thus, option D is correct.

Hugo de Vries was a Dutch botanist, one of the independent rediscoveries of Mendelism, put forward his views regarding the formation of new species in 1901. He also met some of the objections found in Darwins theory. According to him, new species are not formed by continuous variations but by sudden appearance of variations, which he named as mutations. 

In a random mating population in equilibrium, mutations bring about a change in gene frequency. Mutations are non-directional.

The concept of sudden genetic change which breeds true in a species is represented as a mutation. Any sudden or spontaneous change in character which is inheritable is known as mutation. It is defined as the changing of the structure of a gene, resulting in a variant form which may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes. 

Mutation theory of evolution was proposed by Hugo De Vries. According to him, new species are not formed by continuous variations but by sudden appearance of variations which he named as mutations. Hugo de Vries stated that mutations are heritable and persist in successive generations. He conducted his experiments on Oenothera Lamarckiana, (evening primrose) and found several aberrant types. 

The most successful post-Darwinian saltationist was Hugo de Vries. He dominated evolutionary thought during the first decade of the twentieth century. His theories, which achieved an enormous popularity, grew out of his own experimentation using evening primrose (Oenothera lamarckiana). Thus, option D is correct. 'Father of Genetics' is Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Thomas Hunt Morgan was an American evolutionary biologist, geneticist and embryologist and science author, who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Cyril Dean Darlington was an English biologist, geneticist and eugenicist, who discovered the mechanics of chromosomal crossover, its role in inheritance and therefore its importance to evolution. Thus, other options are wrong.

Neo-Darwinism, Theory of evolution that represents a synthesis of Charles Darwin's theory in terms of natural selection and modern population genetics. The term was first used after 1896 to describe the theories of August Weismann (18341914), who asserted that his germ-plasm theory made impossible the inheritance of acquired characteristics and supported natural selection as the only major process that would account for biological evolution. A few supporters of neo darwinism are Romanes, Wallace, Fisher, Huxley, Ford, Haldane, Sewall Wright, Ernst Haeckel, August Weismann, Herbert Spencer and Hugo de Vries etc. 

• In biology, a mutation is the alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA.
•  Mutations result from errors during DNA replication or other types of damage to DNA such as may be caused by exposure to radiation or carcinogens.
• Hence, gene frequency in a population remains stable, unless and until there is a mutation. 
• So, the correct answer is 'Mutation'.