Multiple choice Chromosome number is fixed for a species fixed for a community fixed for a ecosystem fixed for a biosphere Reveal answer Fill a bubble to check yourself A Correct answer Explanation Chromosome number is fixed for a species. The lowest number is seen in Haplopapas gracilis (Asteracease), i.e. 2n = 4 and maximum in some Ophiglosum species (pteridophyte), i.e. 2n = 1656.