What are the most common prokaryotes (and the smallest cells)?

The population of bacteria in a petri dish doubles every 40 seconds. the population of the bacteria is initially 400 organisms. what unit is most appropriate for the time at which the number of bacteria is 300? hour bacteria per hour second bacteria per second

Up to what percentage of the world's flora consisted of cycads during the triassic period? 100% 75% 50% 20%

All phases of matter may have a fixed mass