eukaryotic species. In animals they range more than 3,300-fold, and in land plants they differ by a factor of about 1,000. Protist genomes have been reported to vary more than 300,000-fold in size, but the high end of this range (Amoeba) has been called into question.

Genome size in eukaryotes was thought to be proportional to the complexity of an organism but by the mid-20th century it became apparent that closely related species could differ substantially in