Genome Size and the Evolution of New Genes

Despite the simple nature of the genetic code, there is considerable variation in terms of genome size, from the smallest known genomes - including the proteobacterium Candidatus Carsonella ruddii at less than 160 thousand base pairs, to the largest, such as the Japanese flowering plant Paris japonica at around 150 billion.
 
Despite these extremes, bacteria and archaea generally have around 3,000 genes within their genomes. Because prokaryotes have almost no non-coding sequences, this means that their genomes can be relatively small compared to those of eukaryotes. Smaller genomes also mean less to replicate at each round of cell division - which makes logistical sense for fast reproduction.

Eukaryotes typically have somewhere in the region of 20,000 genes, but their genomes are punctuated by long stretches of non-coding sequence - meaning their genome size does not necessarily translate to complexity. 

Paris japonica’s genome may be over fifty times the size of the human genome - but this is due at least in part to vast amounts of non-coding sequence and probably high levels of duplication - not necessarily more novel genes.

So how do organisms evolve new genes? The answer is typ