Tag: other theories of evolution

• Hugo de Vries in 1901 put forward a theory of evolution, called mutation theory. The theory states that evolution is a jerky process where new varieties and species are formed by mutations (discontinuous variations) that function as a raw material of evolution.
• Mutation theory can not explain the phenomenon of mimicry (i.e. the resemblance between mimic and model), protective coloration and relationship between position of nectaries in flowers and length of proboscis of insects that pollinate them.
  
  

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 evolutionary synthesis. The book popularized the work of population genetics to other biologists and influenced their appreciation for the genetic basis of evolution. In his book, Dobzhansky applied the theoretical work of Sewall Wright to the study of natural populations, allowing him to address evolutionary problems in a novel way during his time. Dobzhansky implements theories of mutation, natural selection and speciation throughout his book to explain habits of populations and the resulting effects on their genetic behavior. 

Genecology is the field of science, which uses theories from both ecology and genetics to modify according to the environment, while simultaneously developing resistance.  

First complete theory of evolution was given by Lamarck (1809). According to him, organism are capable of changing their form, size, colour, agility etc.

Biogenetic law was given by Ernst Haeckel in 1868 A.D. It states that ontogamy recaptulates phylogeny.

Heritability is the part of phenotype variation in a population. This can be attributed to genetic variations in the organisms in that population. This is the factor which describes the chances of evolution occurring in that population on the basis of the genetic differences. 

Physical separation of groups preventing the gene flow between them leads to geographical isolation. Incompatible differences in reproductive structures refer to as mechanical isolation. Different periods of attainment of sexual maturity lead to temporal isolation. Hybrid sterility is one of the post-zygotic isolation. Incompatible premating behaviour leading to no attraction between groups for mating is termed as behavioural isolation. Thus, the correct answer is E.

Physical separation of groups preventing the gene flow between them leads to geographical isolation. Incompatible differences in reproductive structures leading to prevention of cross-fertilization refer to as mechanical isolation. Different periods of attainment of sexual maturity lead to temporal isolation. Hybrid sterility is one of the post-zygotic isolation. Incompatible premating behaviour leading to no attraction between groups for mating is termed as behavioural isolation. Thus, the correct answer is B.

Genetic variation results in the evolution. It results due to mutation in the genetic material resulting in a permanent change. The process of natural selection directly creates genetic variation. Natural selection will change the allele frequencies in the population. This in turn will create genetic variation due to loss of certain alleles during natural selection. Mutation and genetic changes occur spontaneously and change in the environment does stimulate it. The higher the heterozygosity in a population, the higher genetic variation is seen in the population. 

Natural selection is a process governed by changes in environmental factors, these factors produce stress on the organisms. That compels the organisms to undergo changes, in case the organism undergoes changes suitable to the environment, that is, it is suited to survive in the environment will also pass on those traits to the next generation, until the next change occurs. This is natural selection.