The genomic content of the nucleus is constant for a given species,whereas the extrachromosomal $DNA$ is found to be variable among the members of a population. Explain.

(N/A) The genomic $DNA$ (nuclear $DNA$) is replicated and distributed through a highly regulated process (mitosis/meiosis),ensuring that every cell of a given species contains a constant and identical amount of genetic material.
In contrast,extrachromosomal $DNA$,such as plasmids in bacteria or $DNA$ in mitochondria and chloroplasts,does not follow the same strict segregation pattern.
Plasmids are small,circular,extrachromosomal $DNA$ molecules that can be gained or lost through horizontal gene transfer (conjugation,transformation,transduction).
Similarly,the number of organelles like mitochondria varies depending on the metabolic activity of the cell. Since these organelles contain their own $DNA$,their variable copy number leads to variation in the total amount of extrachromosomal $DNA$ among different members of a population.