It had been found that the proportion of non-repetitive DNA can vary a lot between species. Some E. coli as prokaryotes only have non-repetitive DNA, lower eukaryotes such as C. elegans and fruit fly, still possess more non-repetitive DNA than repetitive DNA. Higher eukaryotes tend to have more repetitive DNA than non-repetitive ones. In some plants and amphibians, the proportion of non-repetitive DNA is no more than 20%, becoming a minority component.