NEET Practice Questions (MCQs) with Answers & Solutions

(d) According to Hardy-Weiberg principle, allele frequencies in a population are stable and is constant from generation to generation allele frequencies in a population will remain constant over generation only if the following condition are met
(i) There is no mutation no gene flow and all mating is random.
(ii) All genotypes reproduce equally well (i.e. no natural selection). But, all there conditons rarely met in nature.

(c) The analogous organs are not anatomically similar structures though they perform similar functions. Hence, analogous structures are a result of convergent evolution different structures evolving for the same function and hence, having similarity. Homologous organs developed along different direction due to adaptations to different needs. This is divergent evolution and the structures are homologous.

Population can be defined as a group or assemblage of organisms of the same species that live at a given time in a particular area. In human beings a dominant X-linked gene is necessary for formation of colour sensitive cells the cones, in the retina of eye. The recessive form of this gene is incapable of producing the colour sensitive cones and homozygous recessive female and homozygous recessive males are unable to distinguish between these two colours. As the isolated population do not have any hereditary diseases like colourblindness, so they do not spread accordingly. 

According to the theory of inheritance of acquired characters of Lamarck the Wrestlers, who developed strong body muscles in their life time, must pass this character onto their progeny, but this is not found true. 

Gene pool is defined as the sum total of genes present in a Mendelian population. The study of gene pool tells us the total number of genes, their kinds and variety present in the population.

For a normal distribution the mean, median and mode are actually equivalent. 

(c) Evolution is the sequence of gradual changes which take place in the primitive organisms over million of years in which new species are produced. It is through the constant process of evolution taking place in the organisms since the origin of life that such an enormous variety of plants and animals have come to exist on this earth at present.   

(a) In the devonian period fishes were abundant in fresh water deposits, so that this period is called the age of fishes. By this time some fishes had already invaded the seas. the devonian period shows that much of the land was subjected to seasonal droughts in which abundant rainfall alternated with dry periods in which streams dried up. These conditions had a major influence on the history of fishes and development of terrestrial animals. At the end of the devonian appeared the first land vertebrates, the amphibians.

(b) Genetic drift is the random change in the frequency of alleles in a population over successive generations due to sampling error in the gametes. Each new generation differs from its parental generation with regard to allele frequencies simply because of random variation in the distribution of gametes. Over time, this may lead to certain alleles becoming fixed and others being lost altogether by chance. This process is more rapid in smaller populations or when the alleles are concerned confer no apparent benefit compared to their counterparts. hence, genetic drift can ultimately cause loss of genetic diversity if there are no counteracting factors.

(b) Because there are no living entities possible without the coded organic elements to define their required composite elements, Nucleic acids, are considered the most essential, with the conclusion that it is programmed with sufficient types and number of nucleic-acids. Enzymes and proteins are encoded through critically sequenced nucleic-acids and therefore only exist if programmed nucleic-acids are used.

(b) 

(c) There are some rare cases in medical literation which could be interpreted  as atavisms, that is the reappearance of our ancestor's organs, in which more prolonged traits, already lost by human beings throughout evolution, are expressed again. Such is the case of supranumerary mammary glands, sacral tail etc.