Evolution Test 8

Mutations can be induced by several methods. The three general approaches used to generate mutations are radiation, chemical and transposon insertion.
In addition to X-rays, other types of radiation treatments that have proven useful include gamma rays and fast neutron bombardment. These treatments can induce point mutations (changes in a single nucleotide) or deletions (loss of a chromosomal segment).
Chemical mutagens work mostly by inducing point mutations. Point mutations occur when a single base pair of a gene is changed. These changes are classified as transitions or transversions. Two major classes of chemical mutagens are routinely used. These are alkylating agents (such as ethyl methane sulphonate (EMS), ethyl ethane sulphonate (EES) and base analogs (5-bromouracil and 2-aminopurine).
Therefore, the correct answer is option D.

Mutations are permanent changes in the DNA. However most mutations are neutral; they either make no change in the expression of any gene, or the changes made do not affect the function of any gene product.

Mutation can be defined as a sudden heritable change in the genetic material of any organism.The cause of mutation is Changes in DNA, Changes in chromosome and  Changes in gene.For example, during cell division, the cell makes a copy of its DNA and sometimes the copy is not quite perfect. That small difference from the original DNA sequence is a mutation. Mutations can also be caused by exposure to specific chemicals or radiation. These agents cause the DNA to break down.

Mutations are the main cause for the evolutionary changes. In this, there will be a sudden or induced change in the sequence of DNA. This mutated gene whether dominant or recessive if selected by nature, through natural selection, spreads to other generations. 

Sexual reproduction involves the formation and fusion of gametes.
This requires formation of gametes with meiosis in diploid organisms or meiosis taking place in zygote if the organism is haploid. Due to meiosis, only 50% of the genetic material is passed to the next generation and fusion of gametes results in a unique combination of the genome.
While asexual reproduction results in offsprings with exact genetic material as their parent reducing chances of variations.
So, the correct option is 'Sexual reproduction'.

Darwinism is an evolutionary theory proposed by Charles Robert Darwin, an English Naturalist. He believed that evolution is a gradual, rather than a sudden biological event. His theory was based on several facts, observations and inferences. They are 1) overproduction, 2) constancy in population, 3) struggle for existence, 4) natural selection.
The prodigality of production or overproduction: Every organism tends to increase its population in large proportions. For example, Paramecium divides by binary fission at the rate of three to four times a day. At this rate, the volume of all the paramecia equals to 10,000 times that of the earth at the end of the 9000th generation in the absence of any check.
Constancy in population: However, such an abnormal increase is not noticed in the population of any species in nature as the offspring die in large number before reaching the reproductive age. It is true that the food and the other sources do not increase in the same proportion as that of the population.

Struggle for existence: As the food sources are limited, severe competition exists among the members of a population. Darwin called it a struggle for existence.

Natural selection: The organisms with less reproductive success are not represented in future generations, however, fit they may be in the struggle for existence. This is called the Natural selection. Herbert Spencer called this phenomenon Survival of the fittest.

Darwinism failed to explain the mechanism by which variations occur. Thus Darwin faced the criticism "DARWINISM EXPLAINS THE SURVIVAL OF THE FITTEST BUT NOT THE ARRIVAL OF THE FITTEST".

So, the correct option is 'It does not explain variations with heredity'

Hugo de Vries, a Dutch botanist proposed mutation theory to explain the mechanism of evolution. His theory was published in 1901 in his book "Die Mutation Theorie". He performed experiments on the evening primrose.
According to him, mutations are sudden and heritable changes which are subjected to natural selection. The frequency of a mutated gene in the population is expected to increase if the gene is selected by nature.

It is a long-standing observation that most mutations are recessive. That is, they do not lead to visible phenotypic effects when in heterozygous combination with the wild-type allele.
Recessive disease mutations are much more common than those that are harmful even in a single copy, because such "dominant" mutations are more easily eliminated by natural selection.

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.

Lamarckism or theory of use and disuse has been disproved in this case. It states that animals acquired characteristics after using certain physical traits constantly.

The earlier organisms were simpler. They gradually changed into complex organisms. They are interrelated because of common origin. They have common shelter and environment. Evolution is generally slow, continuous, irreversible and progressive. The most important requirement for the evolution is variation. The ultimate source of organic evolution is the mutation. One of the most important factors of the development of a new species is the geographical isolation. The ultimate source of organic variation is not natural selection, sex reproduction and hormonal action. Thus, option A is correct.

Geographical isolation is a major factor in the speciation of organisms that reproduce sexually because it interrupts with gene flow. In most of the cases, gene flow must be stopped so that sub-populations become genetically isolated. Changes in allele and genotype frequencies within the populations, as a result of the effect of natural selection on the range of phenotypes produced by mutation and sexual recombination, lead to the formation of races and sub-species.

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.

A gene pool is the collection of different genes within an interbreeding population. The concept of a gene pool usually refers to the sum of all the alleles at all of the loci within the genes of a population of a single species. This is the basic concept behind the theory of natural selection.

 Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the soot-covered surroundings. The phenomenon provides an excellent exapmle of operation of selection in natural conditions.

Industrial melanism, therefore, presents an excellent example of natural selection (proposed by Darwin), but it is not the exapmle of acquired characters proposed by Lamarck.

In caves, due to absence of light, the body of the animal lacks pigmentation. eg: Proteus anguinus. In pythons and related snakes rudimentary pelvic girdle and traces of hind limb are present. They form small clawed projections externally, but internally there are vestiges of an ilium, femur, tibia and a claw. In acquatic birds and flying frog, the feet are webbed which sustain it in the prolonged leaps to which it is adapted.

Genetics and the Origin of Species is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky. It is regarded as one of the most important works of the modern synthesis, and was one of the earliest.

The book genetics and origin of species which deals with theory of evolution was written by Theodosius Dobzhansky . it is regarded as one of the most important work of the modern evolutionary synthesis. Charles Darwin was developed the theory of evolution in the famous book on origin of species by means of natural selection.

Differences in a characteristic that can be clearly observed in a population is known as discontinuous variation. Occurence of 4 horns instead of 2 in goat is an example of Discontinuous variation.