What is the difference between primary succession an secondary succession

Primary succession occurs following an opening of a pristine habitat, for example, a lava flow, an area left from retreated glacier, or abandoned strip mine.

In contrast, secondary succession is a response to a disturbance, for example, forest fire, tsunami, flood, or an abandoned field.

chromosomes carry the genetic information for organisms. also, chromatin is the thread like dna which is located in the nucleus of an organism.