Question

 The Complex forms of organisms evolved probably because...

 A. The type and nature of Genome organization in sexually reproducing organisms. 

 B. Exactly replicated copy of parent genome transferred to offspring.

 C. Complex forms of organisms existed since beginning of the life on earth.

 D. None of the above

Answer 1

Option A

Second option is incorrect because exactly replicated copy of parent genome is not transferred to the offsprings. Instead parent genome undergoes crossing over and independent assortment and then is transferred to the progeny.

Third option is incorrect because when life on earth originated, it was simple unicellular.

First option is correct because the nature and type of genome Organisation in different organisms determine genome complexity. This is not to be related with the size of the genome. It is not always necessary that the organism having largest genome size is more complex. But the genome organisation is the thing which makes different organisms complex.

For example, the bacterial genome is simple because it does not contain introns and any repetitive sequence whereas the Eukaryotic genome contains both are them.

The bacterial genome is simply packed inside the nucleoid where as the Eukaryotic genome is extensively packed with the help of histone proteins.

Apart from genome organisation, sexual reproduction have played a vital role in the evolution of complex organisms. This is because sexual reproduction involves formation and fusion of gametes.

Gametes are haploid cells formed from germline cells by reduction division. During this process, they undergo crossing over and independent assortment, both of which are responsible for the great diversity of organisms that we see on the earth. A third factor is the random fertilization of these gametes. This is also important in generating variations.

Both genome organisation and sexual reproduction are important in giving rise to Complex forms of organisms.