Which type of succession (primary or secondary) is going to have the biggest impact on an ecosystem?

Secondary succesion because secondary succession follows a major disturbance, such as a fire or a flood.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.