Why does a population not level off during the same year it reaches zero population growth ?

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

This question is only for applicants to scholars for medicine or scholars for dental medicine: what aspects about medicine (or dental medicine) intrigue you? describe how these aspects influence your life. (100-650 words)

About how much of the cell mass is watet