Mutational theory of evolution - class-X

Hugo de Vries gave a theory of evolution, called 'Mutation theory' which states that evolution is a jerky process where new varieties and species are formed by mutation.

Hugo de Vries proposed the Mutation theory (A=3). Julian Huxley is associated with the modern synthesis and the multiplication of species (B=2). Jean Baptiste Lamarck proposed the inheritance of acquired characters (C=1).

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'.

Mutations are sudden changes in the characteristics of organisms due to chemical changes in the genetic material. The theory of mutation was proposed by Hugo De Vries. Charles Darwin gave the theory of natural selection and Neo-Darwinism is an advanced version of darwins theory.

The term mutation was introduced by Hugo de Vries, while working on evening primrose. He observed aberrent types in $F _1$ generation of two pure breeding varieties. The sudden appearance of new characters was termed as mutation, which he defined as sudden, discontinuous, inheritable changes in genetic material. 

The concept of sudden genetic change, which breeds true in an organism is visualized 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.

Hugo de Vries studied inheritance of flower colour in Oenothera lamarckiana (evening primrose) and proposed mutation theory that says that mutations are sudden, random, and inheritable and discontinuous variations which serve as raw material for evolution. 

a) Theory of evolution was given by De Vries in 1901 which states that evolution is a process where new species are formed due to mutations that functions as a raw material for evolution.

Example for harmful effect of mutation: Oncogenes are harmful mutations can cause cells to become malignant and can ultimately lead to cancer. Mutations are mostly harmful and sometimes neutral (silent mutations)

According to Dobzhansky, mutations, which help organisms in its survival, in the changing environment are accumulated in its genetic composition by natural selection. Mutations are now considered as the ultimate source of organic evolution. By mutations, some old genes can be replaced by new genes in a population to develop changes and thus, mutations play important part in the process of organic evolution.
Thus, the correct answer is option (D), 'Mutation'.

Hugo de Vries gave mutation theory and felt the importance of chance events i.e., mutations during evolution. This was against Darwinian view of evolution as a slow directional process. Mutations are random chance events and result in sudden evolution of characters in a single or few generations.

Mutations are the raw materials of evolution. 

It is sudden heritable change in germplasm.

According to Devries the evolution is very fast like horse running

movement, but not slowly like snails movement as said by Darwin.

Devries also said that there are no middle forms between the ancestor

and new species.

Point mutation refers to the single nucleotide change in genes or single amino acid change in proteins. These changes lead to variability in population and ultimately leads to evolution. Meiosis during sexual reproduction produces new combination of already existing alleles and genes through crossing over but does not creates any new alleles. Gene duplication and divergences are rare events as compared to point mutation. Chromosomal aberrations will bring changes in entire chromosome, not individual genes and / or proteins.

Hugo de Vries, a Dutch Botanist formulated the Mutation theory. According to him, "new species are not formed by continuous variations but by the sudden appearance of variations", which he named as variations. He stated that mutations are heritable and persisted in successive generations.

De Vries discovered new forms among a display of the evening primrose (Oenothera lamarckiana) growing wild in an abandoned potato field. Taking seeds from these, he found that they produced many new varieties in his experimental gardens; he introduced the term mutations for these suddenly appearing variations.

Hugo de Vries had discovered different morphological forms/abberants/variations in primrose/ Oenothera lamarckiana 

According to De Vries theory of evolution,

According to De Vries theory of evolution:

Hugo de Vries proposed the mutation theory .He worked on a flowered evening primrose, he observed the sudden appearance of several expressions

Hugo de Vries after his work on Evening Primose, put forth his theory explaining the structural changes in gene structures, called mutation as the cause of variations. Only large, single step and abrupt mutation termed as saltation are capable enough to drive the process of evolution.

• Mutations are the sudden changes that takes place in the DNA sequence of an organism causing structural changes in genes. 
  
• These are the permanent changes that can be either induced or occur naturally leading to the variation in the populations. Mutations is essential for speciation since variations are the raw material for evolution.
  

De Vries gave his mutation theory on organic evolution while working on Oenothera lamarckiana. Oenothera lamarckiana is an annual plant commonly called as evening primose. De Vries in his experiment observed that original plant showed some offsprings with different phenotypes. These mutations were passed from offsprings to their progeny. However, late it was observed that the variations were due to chromosomal segregations and not due to mutations.

• For a mutation to be evolutionary successful, it must occur in Germplasm DNA since germline mutations are the only one that can be passed on to offspring, when either a mutated sperm or oocyte come together to form a zygote.
  
• After this fertilization event occurs, germ cells divide rapidly to produce all of the cells in the body, causing this mutation to be present in every somatic and germline cell in the offspring; this is also known as a constitutional mutation.
  

Concept of mutations was put forth by Hugo de Vries who worked on evening Primose. He stated that mutation causes evolution and not the minor variations that were suggested by Darwin. Mutations are sudden, random and directionless while Darwinian variations are small and directional.

• The theory of mutation given by Hugo de Vries suggested that evolution is fueled by the occurrence of the discontinuous process called mutation, that arises in the genetic material suddenly and are transmitted to the next generation. 
• These mutations serve as raw material for evolution as they may provide a selective advantage to an individual. The selective advantage would allow an individual to reproduce successfully and hence, the natural selection would lead to evolution.

• Hooke's reputation in the history of biology largely rests on his book Micrographia, published in 1665. 
• Micrographia contains some physiological descriptions of Minute Bodies made by Magnifying Glasses with Observations and Inquiries through various lenses.
  
• On the Origin of Species (or, more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life), published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology.
• Hugo Marie de Vries was a Dutch botanist and one of the first geneticists.
• He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution.
• A swan neck flask is a particular shape of plastic or glass tube leading into a test tube or other vessel.
• The "swan neck" significantly slows down the motion of air through the tube, and particles in the air, such as bacteria, become trapped on moisture on its inner surfaces. Louis Pasteur used  Swan-necked flask experiment for supporting the idea of the germ theory of disease.
• So, the correct answer is 'A- 4, B- 3, C- 1, D- 2'.

Recaptulation theory was modified in the light of evolution as biogentic law by a German biologists - Ernst Haeckel in 1968 AD. It states that ontogeny repeats phylogeny which means that an individual during its own development (ontogeny) passes through ancestral listor (Phylogeny).

A transformation is an adjustment in DNA, the inherited material of life. A creature's DNA influences what it looks like, how it carries on, and its physiology. So an adjustment in a living being's DNA can cause changes in all parts of its life. Changes are basic to advancement; they are the crude material of hereditary variety.                                                                             

So, the correct option is 'Mutations'.

Germplasm is living hereditary assets, for example, seeds or tissues that are kept up with the end goal of creature and plant reproducing, protection, and other research employment. Germplasm accumulation is vital for the support of organic decent variety and sustenance security.

According to De Vries theory of evolution:

Variation was first explained by Hugo De Vries in 1901 while studying evening primrose species. He suggested that species are not formed by continuous changes but with sudden changes called mutation. Thus, the correct answer is 'De Vries.'

Hugo De Vries gave Mutation theory in 1901. He worked on plant Oenothera lamarckiana, commonly known as evening primrose and found several aberrant types. When the plant was self-pollinated and its seeds were allowed to grow, the majority of F$ _1$ plants were similar to the parents, but a few were different plants. Same results were found in F$ _2$ generation. He resulted in that origin of species is through sudden, large changes of traits from another species and these sudden changes are due to Mutation in the gene pool which passes from one generation to another. Later on, it was revealed that most of the variants isolated from Oenothera lamarckiana were due its anomalous chromosome behaviour i.e., chromosome forms multiple rings at meiosis and chromosomal end segments only involves in recombination (low-level crossing over) and plant shows complex heterozygosity i.e., during meiosis maternal and paternal chromosomes are arranged in alternate order. Thus, the correct answer is ‘Complex heterozygote with anomalous chromosome behaviour.’

1. The work of Thomas Malthus 'Principle of population' inspired Darwin's study of evolution.
   2. Paul Kammarer studied the pattern of inheritance on Proteus anguimia, commonly called 'The midwife toad'.
   3. Hugo de Vries brought forward the idea of mutations after his Workin on Oenothera lamarckiana (evening primose).
   4. Bernard kettleweli studies industrial melanisation on Biston betularia.
   So, the correct option is 'All are correct'.